Division of Pulmonary and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21224
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ABSTRACT |
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To determine the role of endothelium
in hypoxic pulmonary vasoconstriction (HPV), we measured vasomotor
responses to hypoxia in isolated seventh-generation porcine pulmonary
arteries < 300 µm in diameter with (E+) and without
endothelium. In E+ pulmonary arteries, hypoxia decreased the vascular
intraluminal diameter measured at a constant transmural pressure. These
constrictions were complete in 30-40 min; maximum at
PO2 of 2 mmHg; half-maximal at
PO2 of 40 mmHg; blocked by exposure to
Ca2+-free conditions, nifedipine, or ryanodine; and absent
in E+ bronchial arteries of similar size. Hypoxic constrictions were
unaltered by indomethacin, enhanced by indomethacin plus
NG-nitro-L-arginine methyl ester,
abolished by BQ-123 or endothelial denudation, and restored in
endothelium-denuded pulmonary arteries pretreated with
1010 M endothelin-1 (ET-1). Given previous demonstrations
that hypoxia caused contractions in isolated pulmonary arterial
myocytes and that ET-1 receptor antagonists inhibited HPV in intact
animals, our results suggest that full in vivo expression of HPV
requires basal release of ET-1 from the endothelium to facilitate
mechanisms of hypoxic reactivity in pulmonary arterial smooth muscle.
vascular smooth muscle; internal diameter; calcium; acetylcholine; U-46619; potassium chloride
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INTRODUCTION |
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OVER THE LAST DECADE, two fundamentally different hypotheses about the mechanisms of hypoxic pulmonary vasoconstriction (HPV) have emerged. According to one (73), hypoxia inhibits voltage-dependent potassium (KV) channels in plasma membranes of pulmonary arterial myocytes, leading to depolarization, Ca2+ influx through voltage-dependent Ca2+ channels, and contraction. According to the other (50), hypoxia acts on endothelium to stimulate production and release of the potent vasoconstrictor peptide endothelin (ET)-1, which mediates HPV by activating ETA receptors on smooth muscle. Both hypotheses have considerable experimental support. On one hand, hypoxia inhibited KV currents, increased membrane potential and intracellular Ca2+ concentration ([Ca2+]i), and caused contraction in isolated pulmonary arterial smooth muscle cells (7, 8, 15, 42, 47, 53, 54, 56, 70, 82). On the other, ET-1 receptor antagonists blocked HPV in intact animals (23, 24, 50, 71, 78).
The major site of HPV is thought to be small distal pulmonary arteries
(1, 21, 59). In myocytes isolated from distal pulmonary
arteries of the pig, we found that hypoxia inhibited KV
channels, increased [Ca2+]i, and decreased
cell length; however, these effects were quite small (58).
If the cells were pretreated with a low concentration of ET-1
(1010 M), which itself had no effect on cell length or
[Ca2+]i, the magnitude of hypoxic
contraction increased eightfold. Because ET-1 receptor antagonists
inhibited HPV in intact animals (23, 24, 50, 71, 78),
these results suggested that full expression of HPV in vivo might
require release of ET-1 from the endothelium to facilitate mechanisms
of hypoxic reactivity in pulmonary arterial smooth muscle.
The purpose of the present study was to test this possibility. First, we characterized the time course, PO2 dependence, and Ca2+ dependence of hypoxic constriction in small [intraluminal diameter (ID) < 300 µm] distal porcine pulmonary arteries and determined whether hypoxic vasoconstriction occurred in bronchial arteries of similar size. Next, we determined whether hypoxic constriction in pulmonary arteries was endothelium dependent and performed experiments to clarify the mechanism of this dependence.
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METHODS |
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Preparation of isolated arteries. Male pigs (20-25 kg) were anesthetized with ketamine (30 mg/kg im) followed by pentobarbital sodium (12.5 mg/kg iv). After the animal was exsanguinated from the femoral arteries, the lungs were rapidly removed and placed in ice-cold Krebs-Ringer bicarbonate (KRB) solution containing (in mM) 118.3 NaCl, 4.7 KCl, 1.2 MgSO4, 1.2 KH2PO4, 2.5 CaCl2, 25.0 NaHCO3, and 11.1 glucose. Under a dissecting microscope, 1-mm segments of pulmonary arteries (OD 100-150 µm) were isolated from seventh-generation branches in the left upper lobe. Bronchial arteries of similar size were isolated from the outer surface of segmental bronchi. The vessels were placed in a chamber filled with KRB solution, cannulated at one end with a glass micropipette, and secured with 12-0 nylon monofilament suture. KRB solution was infused slowly through the pipette until the artery was completely filled. In some pulmonary arteries, endothelial cells were disrupted by gently rubbing the intraluminal surface with a steel wire (diameter 70 µm). These vessels were then perfused with 2 ml of air bubbles followed by 2 ml of KRB solution (perfusion pressure < 5 mmHg). The other end of the vessel was cannulated with a second micropipette filled with KRB solution. Both cannulas were connected to a reservoir that was adjusted to set the transmural pressure (Ptm) to the desired value. Ptm was measured with a pressure transducer positioned at the level of the vessel lumen. The chamber was covered, and the vessels were superfused at 20 ml/min with recirculating KRB solution (total volume 50 ml) gassed with 16% O2-5% CO2-79% N2 and maintained at 37°C. The same gas mixture flowed over the surface of the superfusate in the covered chamber. To measure the vascular ID, the chamber was placed on the stage of an inverted microscope (Nikon TMS-F) connected to a video camera (Panasonic CCTV camera). The vascular image was projected onto a video monitor, and the ID was determined with a video dimension analyzer (Living Systems Instrumentation, Burlington, VT). ID and Ptm were recorded continuously (Gould, Cleveland, OH).
Experimental protocols.
Initially, isolated arteries were allowed to equilibrate for 20 min at
a Ptm of 10 mmHg. Ptm was then increased to 20 (pulmonary arteries) or 40 (bronchial arteries) mmHg and held constant.
To test viability, the vessels were exposed first to KCl (60 mM) and
then to the thromboxane A2 agonist U-46619
(108 M) followed by acetylcholine (ACh;
10
6 M). After the responses had stabilized (5-10
min), the agonists were washed out of the chamber by 15-20 min of
nonrecirculating superfusion with fresh KRB solution. Vessels in which
the ID decreased <30% after KCl and U-46619 were excluded.
Endothelium-intact (E+) vessels were excluded if ACh reversed the
U-46619 contraction by <50%. These criteria were not applied to E+
pulmonary arteries subjected to Ca2+-free conditions or
nifedipine (see below). Endothelium-denuded (E
) vessels were excluded
if ACh caused any vasodilation. In some preparations, viability tests
were repeated at the end of the experiment.
Drugs.
ACh, Indo, and L-NAME were purchased from Sigma (St. Louis,
MO); BQ-123 and ET-1 were from American Peptide (Sunnyvale, CA); U-46619 was from Cayman Chemical (Ann Arbor, MI); and nifedipine, caffeine, and ryanodine were from Calbiochem (La Jolla, CA). Stock solutions of ACh, L-NAME, ET-1, and caffeine were prepared
each day in deionized water and stored at 4°C until used. Indo was dissolved each day in an aqueous solution of NaHCO3
(2.35 × 102 M). Stock solutions of BQ-123 and
nifedipine in ethanol and ryanodine in dimethyl sulfoxide were stored
at
60°C and diluted with deionized water before use. Concentrations
are expressed as final molar concentrations in the superfusate.
Data analysis.
t-Tests and one-, two- or three-factor analysis of variance
were used for statistical analysis of the data, taking repeated measures into account when appropriate. When analysis of variance yielded a significant F-ratio, the least significant
difference was calculated to permit pairwise comparison among means or
Dunnett's test was used to compare means to a control value.
P values 0.05 were taken to indicate significance.
Values are means ± SE. On each experimental day, two vessels from
the same animal were subjected to different protocols; therefore,
n is the number of both animals and vessels in each group.
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RESULTS |
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Viability tests.
Under normoxic conditions at the beginning of the experiment, the ID
measured at a Ptm of 20 mmHg (ID20) was greater
in E+ than in E pulmonary arteries (Table
1). KCl and U-46619 caused vigorous
constriction in both E+ and E
arteries. ACh reversed constrictions
induced by U-46619 in E+ arteries but had no effect in E
arteries.
Responses of E+ bronchial arteries to KCl, U-46619, and ACh were
similar to those of E+ pulmonary arteries.
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Responses of pulmonary and bronchial arteries to hypoxia.
Decreasing the O2 concentration from 16 to 7, 4, or 0% for
30 min caused PO2 in the chamber superfusate to
decrease rapidly from 114 ± 1 to 49 ± 1, 29 ± 1, and
2 ± 3 mmHg, respectively (Fig. 2A). On reoxygenation with
16% O2, PO2 increased rapidly,
reaching 113 ± 2 mmHg at 60 min. When the O2
concentration was maintained at 16% throughout the experiment,
PO2 averaged 116 ± 2 mmHg.
PCO2 and pH were constant at 33 ± 0.2 mmHg and 7.40 ± 0.003, respectively.
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Ca2+ dependence of HPV.
Vasoconstrictor responses to KCl were virtually abolished in
pulmonary arteries subjected to Ca2+-free conditions or
nifedipine (ID20 =
9 ± 6 and
7 ± 2% of control ID20, respectively, compared with
69 ± 2% in untreated arteries; P < 0.0001;
Table 1). Vasoconstrictor responses to U-46619 were also reduced but
less severely (
ID20 =
26 ± 5 and
18 ± 4% of control ID20, respectively, compared with
46 ± 2% in untreated arteries; P < 0.0001;
Table 1). Vasodilator responses to ACh were not altered
(
ID20 = 91 ± 14 and 74 ± 16% of
U-46619-induced constrictions, respectively, compared with 112 ± 5% in untreated arteries; P > 0.05; Table 1).
Caffeine did not alter the vasomotor tone in arteries treated with
ryanodine (
ID20 = 11 ± 7%; P = 0.13).
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Endothelium and endothelin dependence of HPV.
As shown in Fig. 5, ID20 in
E+ pulmonary arteries exposed to 4% O2 for 60 min
decreased relative to ID20 in normoxic E+ arteries (ID20 at 60 min =
71 ± 14 and
25 ± 10 µm, respectively; P < 0.0001). In E
pulmonary
arteries, this hypoxic vasoconstriction was abolished
(
ID20 at 60 min =
4 ± 10 and
6 ± 14 µm in normoxic and hypoxic E
arteries, respectively;
P = 0.999). Compared with untreated E+ arteries,
ID20 measured before hypoxic exposure in untreated E
arteries was decreased (162 ± 9 µm; P < 0.01).
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DISCUSSION |
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HPV has been thoroughly studied in intact animals and isolated lungs. These preparations provide consistent and physiologically relevant responses but impose significant limitations on mechanistic investigation. More reduced preparations permit more precise intervention but may yield inconsistent responses of uncertain relevance (63). In the present study, we used small distal porcine pulmonary arteries to determine whether HPV was endothelium dependent. We chose the pig as our experimental animal because HPV is vigorous in this species (9, 62) and porcine lungs are large enough to permit dissection of small distal pulmonary arteries. We studied seventh-generation pulmonary arteries < 300 µm in diameter because small distal pulmonary arteries are thought to be the major site of HPV (1, 21, 59). We measured changes in vasomotor tone as changes in ID at a constant Ptm because HPV normally occurs locally and does not alter pulmonary arterial pressure and because this measurement may more accurately reflect properties of in vivo arteries in which contraction is neither isometric nor isotonic (17).
As shown in Fig. 2, physiological decreases in PO2 caused vigorous sustained vasoconstriction in our preparation. Relative to the gradual vasoconstriction caused during normoxia by intrinsic tone (38, 40), hypoxic vasoconstriction began 5-10 min after the onset of exposure and appeared to be complete within 30-40 min (Figs. 2A and 5). Maximum HPV decreased ID20 62 µm or ~40% of the constrictor response to 60 mM KCl (Fig. 2A, Table 1). HPV was half-maximal at a PO2 of 40 mmHg (Fig. 2B). In isolated and intact lungs, HPV occurred somewhat more rapidly, requiring 10-15 min to achieve initial plateau responses, which were half-maximal at O2 tensions of 30-60 mmHg (3, 9, 61, 62). In isolated ferret lungs, maximum HPV was 38% of the maximum vasoconstrictor response to KCl (16). Thus, in terms of magnitude, PO2 dependence, and temporal characteristics, hypoxic vasoconstriction in our isolated arteries was similar to that in intact and isolated lungs.
Although severe hypoxia caused sustained vasoconstriction in arteries (Fig. 2, 0% O2), it caused vasoconstriction followed by vasodilation in isolated lungs (62). Vasodilation to severe hypoxia was probably caused by deterioration of the vascular smooth muscle energy state, activation of ATP-dependent K+ (KATP) channels, hyperpolarization, decreased Ca2+ influx through voltage-dependent Ca2+ channels, and relaxation (33, 76, 77). This sequence may have not have occurred in our arteries because unlike in isolated lungs perfused at a constant flow, intraluminal pressures (and, therefore, Ptm) did not increase during HPV, resulting in a lower workload on pulmonary arterial smooth muscle and better maintenance of smooth muscle energy state and tone during severe hypoxia.
Vasoconstriction elicited by severe hypoxia (0% O2) was not reversible in isolated arteries (Fig. 2). Indeed, reoxygenation after 0% O2 caused further constriction. Even in arteries exposed to 4% O2, where HPV was reversible, transient constriction was observed on reoxygenation. The mechanism of this constriction remains to be determined; however, because it occurred with reoxygenation, it may have been mediated by reactive oxygen species (27, 79). Injury due to reactive oxygen species may explain depression of the vasoconstrictor responses to KCl and the vasodilator responses to ACh seen after reoxygenation (Fig. 1). Because vasoconstrictor responses to U-46619 (and, therefore, contractile ability) were unchanged, these results suggest that voltage-dependent Ca2+ channels and NO responsiveness in smooth muscle and/or ACh-induced NO production in endothelium were dysfunctional after reoxygenation. Further studies are needed to confirm these results and determine the underlying mechanisms. Because of the possibility of reoxygenation injury, we utilized single exposures to 4% O2 to elicit HPV in subsequent experiments.
In more proximal pulmonary arteries, hypoxic responses were typically triphasic (early transient contraction followed by relaxation and late sustained contraction) and did not occur unless the arteries were subjected to 0% O2 after some special treatment such as precontraction with vasoactive agonists or prolonged exposure to moderate hypoxia (22, 30, 32, 63). In small (OD < 300 µm) distal pulmonary arteries of the cat, increases in isometric tension caused by decreases in PO2 from >400 to 250, 150, 100, 50, or 20 mmHg were transient, and the peaks of these contractions were half-maximal at a PO2 of 100 mmHg (41). These differences may be attributable to species, arterial size or locus, or method of measurement. Because increases in vasomotor tone were measured as increases in isometric tension, deterioration of energy state may have contributed to hypoxic relaxation in proximal pulmonary arteries (33) and the transience of hypoxic constriction in small distal pulmonary arteries (41). We are unaware of previous attempts to assess hypoxic responses in pulmonary arteries from measurements of ID at a constant Ptm.
HPV in intact animals and isolated lungs and hypoxia-induced increases in [Ca2+]i in pulmonary arterial myocytes were inhibited by L-type Ca2+ channel antagonists (2, 8, 28, 45, 67) and potentiated by agonists of these channels (8, 44, 66), indicating that HPV required influx of extracellular Ca2+ through sarcolemmal L-type Ca2+ channels. Our findings that Ca2+-free conditions or nifedipine prevented HPV in isolated pulmonary arteries (Fig. 4) support this view and demonstrate further similarity between the hypoxic responses of our preparation and those of intact and isolated lungs. It has been suggested that inhibition of HPV by Ca2+ channel antagonists could be due to nonspecific decreases in baseline tone (55). Because baseline ID20 in nifedipine-treated E+ arteries was higher than in untreated E+ arteries, this possibility cannot be ruled out.
Some investigators reported that depletion of Ca2+ stores in the SR with ryanodine and caffeine, which activate SR ryanodine receptors, or thapsigargin and cyclopiazonic acid, which inhibit SR Ca2+ uptake, inhibited hypoxia-induced increases in myocyte [Ca2+]i (15, 56, 70). Our observations that ryanodine blocked HPV in isolated pulmonary arteries are consistent with these findings and support the proposal that HPV is triggered by release of SR Ca2+, which then acts on sarcolemmal ion channels to cause depolarization and Ca2+ influx through voltage-dependent Ca2+ channels (15, 52). Alternatively, HPV could be mediated by an initial influx of Ca2+ through voltage-dependent Ca2+ channels, leading to Ca2+-induced Ca2+ release from the SR and sustained elevation of [Ca2+]i (8). Further work is required to evaluate these possibilities.
Although hypoxia caused vigorous vasoconstriction in pulmonary arteries, it did not alter the ID in bronchial arteries (Fig. 3). These results are consistent with previous studies (6, 48) of systemic arteries in which hypoxia had no effect or caused vasodilation. We used bronchial arteries because these vessels could be isolated from the same organ and studied in the same manner as pulmonary arteries, thereby minimizing the influence of methodological factors on our results. The only methodological difference was Ptm, which was higher in bronchial arteries to reflect in vivo conditions; however, it is unlikely that the higher Ptm prevented hypoxic constriction in bronchial arteries because these vessels constricted vigorously to KCl and U-46619 (Table 1). It is more likely that the hypoxic responses of pulmonary and bronchial arteries were different due to intrinsic differences in reactivity.
The similarities in temporal characteristics, PO2 dependence, and Ca2+ dependence of hypoxic vasoconstriction between small porcine pulmonary arteries and isolated and intact lungs and the absence of this response in bronchial arteries suggested that studies in small porcine pulmonary arteries could help to clarify the mechanisms of in vivo HPV; therefore, we used this preparation to determine if HPV was endothelium dependent.
As shown in Fig. 5, endothelial denudation abolished HPV in these
vessels. This effect was not due to denudation-induced injury to
vascular smooth muscle because E arteries constricted vigorously to
KCl and U-46619 (Table 1). Neither was it due to decreased baseline
vasomotor tone (55) because ID20 before
hypoxic exposure was smaller than in E+ arteries, suggesting that
baseline tone had increased. Rather, it must have been due to
elimination of some endothelial influence on vascular smooth muscle.
Endothelium can release relaxing factors, such as NO and prostacyclin,
and contracting factors, such as endothelin and thromboxane; therefore, HPV could be due to a hypoxia-induced decrease in relaxing factor activity or a hypoxia-induced increase in contracting factor
activity. Alternatively, basal release of endothelial factors might
facilitate the mechanisms of HPV intrinsic to vascular smooth muscle.
To evaluate these possibilities, we determined how Indo,
L-NAME, and BQ-123 altered HPV in E+ arteries and whether
ET-1 restored HPV in E
arteries.
Liu and Sylvester (38) have shown that
L-NAME (3 × 105 M) blocked the
vasodilator responses to ACh in this preparation, indicating inhibition
of NO synthase, and that BQ-123 (3 × 10
6 M) blocked
the vasoconstrictor responses to ET-1, indicating inhibition of
ETA receptors. Measurement of prostaglandins
D2, E2, and F2
, 6-keto
prostaglandin F1
, and thromboxane B2
production by gas chromatography/mass spectrometry indicated that Indo
(10
6 M) blocked cyclooxygenase in isolated proximal
porcine pulmonary arterial rings (Shimoda T, Sylvester J, Undem B, and
Hubbard W, unpublished data). Indo (10
5 M),
L-NAME (3 × 10
5 M), or BQ-123 (3 × 10
6 M) did not alter the vasoconstrictor responses to
KCl or U-46619 in small porcine pulmonary arteries (38).
Finally, ID20 measured before hypoxic exposure was not
different among untreated E+ arteries and E+ arteries treated with
Indo, Indo plus L-NAME, or BQ-123, suggesting similar
baseline vasomotor tone. These results indicate that our
pharmacological interventions had the intended effects on the
endothelium and did not have unintended nonspecific effects on vascular
smooth muscle.
As shown in Fig. 6, HPV was unaltered by Indo, enhanced by Indo plus L-NAME, and abolished by BQ-123. Many studies in isolated and intact lungs (16, 19, 34, 39, 68, 72, 74) have demonstrated enhancement of HPV by inhibitors of cyclooxygenase and NO synthase alone or in combination. Like our results, these data indicate that cyclooxygenase products and NO modulated but did not mediate HPV. In contrast, antagonists of ETA receptors blocked HPV in intact and isolated lungs (11, 14, 23, 24, 50, 57, 71, 78) and acute hypoxia increased ET-1 production in intact and isolated lungs and cultured endothelium (20, 25, 29, 60, 64). These data are consistent with the effects of BQ-123 shown in Fig. 6 and suggest that ET-1 mediated HPV.
Other observations question this possibility. ET-induced pulmonary vasoconstriction, unlike HPV, reversed very slowly (4, 43), perhaps due to prolonged receptor binding (75). ET-1 caused transient vasodilation during HPV, perhaps by activating KATP channels in vascular smooth muscle or ETB receptors and NO production in endothelium (10, 18, 20, 35-37, 80). Some investigators (11, 46, 51) were unable to demonstrate that hypoxia increased pulmonary ET-1 production. Others (20, 64) found that hypoxia-induced increases in ET-1 concentration occurred much later than or did not correlate with HPV. Thus the role of ET-1 in HPV may be more subtle than direct concentration-dependent activation of smooth muscle contraction.
To reconcile these discrepancies as well as the observations that
isolated pulmonary arterial myocytes contract to hypoxia (42, 47,
58), we hypothesized that the basal production of ET-1 by the
endothelium allowed full expression of HPV in vivo by facilitating
mechanisms of hypoxic reactivity in vascular smooth muscle. To test
this hypothesis, we determined whether exposure to a low concentration
of ET-1 (1010 M) would restore HPV in E
pulmonary
arteries. We used 10
10 M because Liu and Sylvester
(38) previously found that this concentration was at the
threshold for contraction in these vessels. As shown in Fig. 7, ET-1
priming almost completely restored HPV in E
arteries
(
ID20 at 30 min =
39 ± 8 µm or ~70% of
the response to 4% O2 in untreated E+ arteries). These
results are supportive of our hypothesis and consistent with previous
observations by Sham et al. (58) in freshly isolated
smooth muscle cells from these vessels in which ET-1 priming
potentiated an otherwise small but significant hypoxic contraction
nearly eightfold.
ET-1 could facilitate HPV in several ways. In pulmonary arterial myocytes, ET-1 priming potentiated hypoxic contraction but did not alter hypoxia-induced increases in [Ca2+]i, suggesting an increase in myofilament Ca2+ sensitivity (58). ET-1 is known to have this effect in both systemic and pulmonary arterial smooth muscle (13, 49), and increased Ca2+ sensitivity has been proposed to contribute to hypoxic responses in precontracted rat pulmonary arteries (54, 72). Other possibilities include an increased open probability of Ca2+ channels (26) and a depolarized resting membrane potential (69). The latter could make sarcolemmal KV channels more susceptible to hypoxic inactivation, thought by some investigators to be an important early step in HPV (73). It was recently suggested that ET-1 might facilitate HPV by preventing hypoxic activation of KATP channels in pulmonary vascular smooth muscle (57); however, glibenclamide, an KATP antagonist, did not alter HPV in isolated ferret lungs exposed to moderate hypoxia (76). Further studies are needed to evaluate these possibilities.
It is possible that agonists other than ET-1 could facilitate HPV. This might explain why ET-1 receptor antagonists sometimes did not inhibit HPV in intact animals (81), isolated lungs (65), or pulmonary arteries (12, 31). In support of this possibility, Sato et al. (57) found that ETA receptor antagonists blocked HPV in intact and isolated rat lungs but not in isolated lungs costimulated with angiotensin II. Such data emphasize that our results should not be extended to other preparations, conditions, or species without experimental confirmation of applicability. Nevertheless, it is interesting to note that the inhibitory effect of ETA receptor antagonists on HPV in vivo has been reasonably consistent across species (5, 14, 23, 24, 50, 57, 71, 78), suggesting that ET-1 may play a pivotal physiological role.
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FOOTNOTES |
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Address for reprint requests and other correspondence: J. T. Sylvester, Division of Pulmonary and Critical Care Medicine, The Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224.
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 20 September 2000; accepted in final form 15 November 2000.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Al-Tinawi, A,
Krenz GS,
Rickaby DA,
Linehan JH,
and
Dawson CA.
Influence of hypoxia and serotonin on small pulmonary vessels.
J Appl Physiol
76:
56-64,
1994
2.
Archer, SL,
Yankovich RD,
Chesler E,
and
Weir EK.
Comparative effects of nisoldipine, nifedipine and bepridil on experimental pulmonary hypertension.
J Pharmacol Exp Ther
233:
12-17,
1985[Abstract].
3.
Barer, GR,
Howard P,
and
Shaw JW.
Stimulus-response curves for the pulmonary vascular bed to hypoxia and hypercapnia.
J Physiol (Lond)
211:
139-155,
1970[ISI][Medline].
4.
Chatfield, BA,
McMurtry IF,
Hall SL,
and
Abman SH.
Hemodynamic effects of endothelin-1 on ovine fetal pulmonary circulation.
Am J Physiol Regulatory Integrative Comp Physiol
261:
R182-R187,
1991
5.
Chen, SJ,
Chen YF,
Meng QC,
Durand J,
Dicarlo VS,
and
Oparil S.
Endothelin-receptor antagonist bosentan prevents and reverses hypoxic pulmonary hypertension in rats.
J Appl Physiol
79:
2122-2131,
1995
6.
Coburn, RF,
Grubb B,
and
Aronson RD.
Effect of cyanide on oxygen tension-dependent mechanical tension in rabbit aorta.
Circ Res
44:
368-378,
1979[ISI][Medline].
7.
Cornfield, DN,
Stevens T,
McMurtry IF,
Abman SH,
and
Rodman DM.
Acute hypoxia increases cytosolic calcium in fetal pulmonary artery smooth muscle cells.
Am J Physiol Lung Cell Mol Physiol
265:
L53-L56,
1993
8.
Cornfield, DN,
Stevens T,
McMurtry IF,
Abman SH,
and
Rodman DM.
Acute hypoxia causes membrane depolarization and calcium influx in fetal pulmonary artery smooth muscle cells.
Am J Physiol Lung Cell Mol Physiol
266:
L469-L475,
1994
9.
De Canniere, D,
Stefanidis C,
Hallemans R,
Delcroix M,
Brimioulle S,
and
Naeije R.
Stimulus-response curves for hypoxic pulmonary vasoconstriction in piglets.
Cardiovasc Res
26:
944-949,
1992[ISI][Medline].
10.
Deleuze, PH,
Adnot S,
Shiiya N,
Roudot Thoraval F,
Eddahibi S,
Braquet P,
Chabrier PE,
and
Loisance DY.
Endothelin dilates bovine pulmonary circulation and reverses hypoxic pulmonary vasoconstriction.
J Cardiovasc Pharmacol
19:
354-360,
1992[ISI][Medline].
11.
Doi, S,
Smedira N,
and
Murray PA.
Pulmonary vasoregulation by endothelin in conscious dogs after left lung transplantation.
J Appl Physiol
88:
210-218,
2000
12.
Douglas, SA,
Vickery-Clark LM,
and
Ohlstein EH.
Endothelin-1 does not mediate hypoxic vasoconstriction in canine isolated blood vessels: effect of BQ-123.
Br J Pharmacol
108:
418-421,
1993[ISI][Medline].
13.
Evans, AM,
Cobban HJ,
and
Nixon GF.
ETA receptors are the primary mediators of myofilament calcium sensitization induced by ET-1 in rat pulmonary artery smooth muscle: a tyrosine kinase independent pathway.
Br J Pharmacol
127:
153-160,
1999
14.
Franco-Cereceda, A,
and
Holm P.
Selective or nonselective endothelin antagonists in porcine hypoxic pulmonary hypertension?
J Cardiovasc Pharmacol
31, Suppl1:
S447-S452,
1998[ISI][Medline].
15.
Gelband, CH,
and
Gelband H.
Ca2+ release from intracellular stores is an initial step in hypoxic pulmonary vasoconstriction of rat pulmonary artery resistance vessels.
Circulation
96:
3647-3654,
1997
16.
Gottlieb, JE,
McGeady M,
Adkinson NF, Jr,
and
Sylvester JT.
Effects of cyclo- and lipoxygenase inhibitors on hypoxic vasoconstriction in isolated ferret lungs.
J Appl Physiol
64:
936-943,
1988
17.
Halpern, W,
and
Kelley M.
In vitro methodology for resistance arteries.
Blood Vessels
28:
245-251,
1991[ISI][Medline].
18.
Hasunuma, K,
Rodman DM,
O'Brien RF,
and
McMurtry IF.
Endothelin 1 causes pulmonary vasodilation in rats.
Am J Physiol Heart Circ Physiol
259:
H48-H54,
1990
19.
Hasunuma, K,
Yamaguchi T,
Rodman DM,
O'Brien RF,
and
McMurtry IF.
Effects of inhibitors of EDRF and EDHF on vasoreactivity of perfused rat lungs.
Am J Physiol Lung Cell Mol Physiol
260:
L97-L104,
1991
20.
Helset, E,
Kjaeve J,
Bjertnaes L,
and
Lundberg JM.
Acute alveolar hypoxia increases endothelin-1 release but decreases release of calcitonin gene-related peptide in isolated perfused rat lungs.
Scand J Clin Lab Invest
55:
369-376,
1995[ISI][Medline].
21.
Herold, CJ,
Wetzel RC,
Robotham JL,
Herold SM,
and
Zerhouni EA.
Acute effects of increased intravascular volume and hypoxia on the pulmonary circulation: assessment with high-resolution CT.
Radiology
183:
655-662,
1992[Abstract].
22.
Holden, WE,
and
McCall E.
Hypoxia-induced contractions of porcine pulmonary artery strips depend on intact endothelium.
Exp Lung Res
7:
101-112,
1984[ISI][Medline].
23.
Holm, P,
Liska J,
Clozel M,
and
Franco-Cereceda A.
The endothelin antagonist bosentan: hemodynamic effects during normoxia and hypoxic pulmonary hypertension in pigs.
J Thorac Cardiovasc Surg
112:
890-897,
1996
24.
Holm, P,
Liska J,
and
Franco-Cereceda A.
The ETA receptor antagonist, BMS-182874, reduces acute hypoxic pulmonary hypertension in pigs in vivo.
Cardiovasc Res
37:
765-771,
1998[ISI][Medline].
25.
Horio, T,
Kohno M,
Yokokawa K,
Murakawa K,
Yasunari K,
Fujiwara H,
Kurihara N,
and
Takeda T.
Effect of hypoxia on plasma immunoreactive endothelin-1 concentration in anesthetized rats.
Metabolism
40:
999-1001,
1991[ISI][Medline].
26.
Inoue, Y,
Oike M,
Nakao K,
Kitamura K,
and
Kuriyama H.
Endothelin augments unitary calcium channel currents on the smooth muscle cell membrane of guinea-pig portal vein.
J Physiol (Lond)
423:
171-191,
1990[Abstract].
27.
Katusic, ZS.
Superoxide anion and endothelial regulation of arterial tone.
Free Radic Biol Med
20:
443-448,
1996[ISI][Medline].
28.
Kennedy, T,
and
Summer W.
Inhibition of hypoxic pulmonary vasoconstriction by nifedipine.
Am J Cardiol
50:
864-868,
1982[ISI][Medline].
29.
Kourembanas, S,
Marsden PA,
McQuillan LP,
and
Faller DV.
Hypoxia induces endothelin gene expression and secretion in cultured human endothelium.
J Clin Invest
88:
1054-1057,
1991[ISI][Medline].
30.
Kovitz, KL,
Aleskowitch TD,
Sylvester JT,
and
Flavahan NA.
Endothelium-derived contracting and relaxing factors contribute to hypoxic responses of pulmonary arteries.
Am J Physiol Heart Circ Physiol
265:
H1139-H1148,
1993
31.
Lazor, R,
Feihl F,
Waeber B,
Kucera P,
and
Perret C.
Endothelin-1 does not mediate the endothelium-dependent hypoxic contractions of small pulmonary arteries in rats.
Chest
110:
189-197,
1996
32.
Leach, RM,
Robertson TP,
Twort CH,
and
Ward JP.
Hypoxic vasoconstriction in rat pulmonary and mesenteric arteries.
Am J Physiol Lung Cell Mol Physiol
266:
L223-L231,
1994
33.
Leach, RM,
Sheehan DW,
Chacko VP,
and
Sylvester JT.
Energy state, pH, and vasomotor tone during hypoxia in precontracted pulmonary and femoral arteries.
Am J Physiol Lung Cell Mol Physiol
278:
L294-L304,
2000
34.
Leeman, M,
de Beyl VZ,
Biarent D,
Maggiorini M,
Melot C,
and
Naeije R.
Inhibition of cyclooxygenase and nitric oxide synthase in hypoxic vasoconstriction and oleic acid-induced lung injury.
Am J Respir Crit Care Med
159:
1383-1390,
1999
35.
Lippton, HL,
Cohen GA,
Knight M,
McMurtry IF,
Gillot D,
Arena F,
Summer W,
and
Hyman AL.
Evidence for distinct endothelin receptors in the pulmonary vascular bed in vivo.
J Cardiovasc Pharmacol
17:
S370-S373,
1991[ISI][Medline].
36.
Lippton, HL,
Cohen GA,
McMurtry IF,
and
Hyman AL.
Pulmonary vasodilation to endothelin isopeptides in vivo is mediated by potassium channel activation.
J Appl Physiol
70:
947-952,
1991
37.
Liska, J,
Holm P,
Owall A,
and
Franco-Cereceda A.
Endothelin infusion reduces hypoxic pulmonary hypertension in pigs in vivo.
Acta Physiol Scand
154:
489-498,
1995[ISI][Medline].
38.
Liu, Q,
and
Sylvester JT.
Development of intrinsic tone in isolated pulmonary arterioles.
Am J Physiol Lung Cell Mol Physiol
276:
L805-L813,
1999
39.
Liu, SF,
Crawley DE,
Barnes PJ,
and
Evans TW.
Endothelium-derived relaxing factor inhibits hypoxic pulmonary vasoconstriction in rats.
Am Rev Respir Dis
143:
32-37,
1991[ISI][Medline].
40.
Madden, JA,
al-Tinawi A,
Birks E,
Keller PA,
and
Dawson CA.
Intrinsic tone and distensibility of in vitro and in situ cat pulmonary arteries.
Lung
174:
291-301,
1996[ISI][Medline].
41.
Madden, JA,
Dawson CA,
and
Harder DR.
Hypoxia-induced activation in small isolated pulmonary arteries from the cat.
J Appl Physiol
59:
113-118,
1985
42.
Madden, JA,
Vadula MS,
and
Kurup VP.
Effects of hypoxia and other vasoactive agents on pulmonary and cerebral artery smooth muscle cells.
Am J Physiol Lung Cell Mol Physiol
263:
L384-L393,
1992
43.
Mann, J,
Farrukh IS,
and
Michael JR.
Mechanisms by which endothelin 1 induces pulmonary vasoconstriction in the rabbit.
J Appl Physiol
71:
410-416,
1991
44.
McMurtry, IF.
BAY K 8644 potentiates and A23187 inhibits hypoxic vasoconstriction in rat lungs.
Am J Physiol Heart Circ Physiol
249:
H741-H746,
1985
45.
McMurtry, IF,
Davidson AB,
Reeves JT,
and
Grover RF.
Inhibition of hypoxic pulmonary vasoconstriction by calcium antagonists in isolated rat lungs.
Circ Res
38:
99-104,
1976[Abstract].
46.
Medbo, S,
Yu XQ,
Asberg A,
and
Saugstad OD.
Pulmonary hemodynamics and plasma endothelin-1 during hypoxemia and reoxygenation with room air or 100% oxygen in a piglet model.
Pediatr Res
44:
843-849,
1998[Abstract].
47.
Murray, TR,
Chen L,
Marshall BE,
and
Macarak EJ.
Hypoxic contraction of cultured pulmonary vascular smooth muscle cells.
Am J Respir Cell Mol Biol
3:
457-465,
1990[ISI][Medline].
48.
Namm, DH,
and
Zucker JL.
Biochemical alterations caused by hypoxia in the isolated rabbit aorta. Correlation with changes in arterial contractility.
Circ Res
32:
464-470,
1973[Medline].
49.
Nishimura, J,
Moreland S,
Ahn HY,
Kawase T,
Moreland RS,
and
van Breemen C.
Endothelin increases myofilament Ca2+ sensitivity in alpha-toxin-permeabilized rabbit mesenteric artery.
Circ Res
71:
951-959,
1992[Abstract].
50.
Oparil, S,
Chen SJ,
Meng QC,
Elton TS,
Yano M,
and
Chen YF.
Endothelin-A receptor antagonist prevents acute hypoxia-induced pulmonary hypertension in the rat.
Am J Physiol Lung Cell Mol Physiol
268:
L95-L100,
1995
51.
Perreault, T,
Stewart DJ,
Cernacek P,
Wu X,
Ni F,
De Marte J,
and
Giaid A.
Newborn piglet lungs release endothelin-1: effect of alpha-thrombin and hypoxia.
Can J Physiol Pharmacol
71:
227-233,
1993[ISI][Medline].
52.
Post, JM,
Gelband CH,
and
Hume JR.
[Ca2+]i inhibition of K+ channels in canine pulmonary artery. Novel mechanism for hypoxia-induced membrane depolarization.
Circ Res
77:
131-139,
1995
53.
Post, JM,
Hume JR,
Archer SL,
and
Weir EK.
Direct role for potassium channel inhibition in hypoxic pulmonary vasoconstriction.
Am J Physiol Cell Physiol
262:
C882-C890,
1992
54.
Robertson, TP,
Aaronson PI,
and
Ward JP.
Hypoxic vasoconstriction and intracellular Ca2+ in pulmonary arteries: evidence for PKC-independent Ca2+ sensitization.
Am J Physiol Heart Circ Physiol
268:
H301-H307,
1995
55.
Robertson, TP,
Hague D,
Aaronson PI,
and
Ward JP.
Voltage-independent calcium entry in hypoxic pulmonary vasoconstriction of intrapulmonary arteries of the rat.
J Physiol (Lond)
525:
669-680,
2000
56.
Salvaterra, CG,
and
Goldman WF.
Acute hypoxia increases cytosolic calcium in cultured pulmonary arterial myocytes.
Am J Physiol Lung Cell Mol Physiol
264:
L323-L328,
1993
57.
Sato, K,
Morio Y,
Morris KG,
Rodman DM,
and
McMurtry IF.
Mechanism of hypoxic pulmonary vasoconstriction involves ETA receptor-mediated inhibition of KATP channel.
Am J Physiol Lung Cell Mol Physiol
278:
L434-L442,
2000
58.
Sham, JSK,
Crenshaw BR,
Shimoda LA,
and
Sylvester JT.
Effects of hypoxia in porcine pulmonary arterial myocytes: roles of KV channel and endothelin-1.
Am J Physiol Lung Cell Mol Physiol
279:
L262-L272,
2000
59.
Shirai, M,
Sada K,
and
Ninomiya I.
Effects of regional alveolar hypoxia and hypercapnia on small pulmonary vessels in cats.
J Appl Physiol
61:
440-448,
1986
60.
Shirakami, G,
Nakao K,
Saito Y,
Magaribuchi T,
Jougasaki M,
Mukoyama M,
Arai H,
Hosoda K,
Suga S,
Ogawa Y,
Yamada T,
Mori K,
and
Imura H.
Acute pulmonary alveolar hypoxia increases lung and plasma endothelin-1 levels in conscious rats.
Life Sci
48:
969-976,
1991[ISI][Medline].
61.
Suggett, AJ,
Mohammed FH,
Barer GR,
Twelves C,
and
Bee D.
Quantitative significance of hypoxic vasoconstriction in the ferret lung.
Respir Physiol
46:
89-104,
1981[ISI][Medline].
62.
Sylvester, JT,
Harabin AL,
Peake MD,
and
Frank RS.
Vasodilator and constrictor responses to hypoxia in isolated pig lungs.
J Appl Physiol
49:
820-825,
1980
63.
Sylvester, JT,
Sham JSK,
Shimoda LA,
and
Liu Q.
Cellular mechanisms of acute hypoxic pulmonary vasoconstriction.
In: Respiratory-Circulatory Interactions in Health and Disease, edited by Scharf SM,
Pinsky MR,
and Magder S.. New York: Dekker, 2001, vol. 157, p. 315-359. (Lung Biol Health Dis Ser)
64.
Takeda, S,
Nakanishi K,
Inoue T,
and
Ogawa R.
Delayed elevation of plasma endothelin-1 during unilateral alveolar hypoxia without systemic hypoxemia in humans.
Acta Anaesthesiol Scand
41:
274-280,
1997[ISI][Medline].
65.
Takeoka, M,
Ishizaki T,
Sakai A,
Chang SW,
Shigemori K,
Higashi T,
and
Ueda G.
Effect of BQ123 on vasoconstriction as a result of either hypoxia or endothelin-1 in perfused rat lungs.
Acta Physiol Scand
155:
53-60,
1995[ISI][Medline].
66.
Tolins, M,
Weir EK,
Chesler E,
Nelson DP,
and
From AH.
Pulmonary vascular tone is increased by a voltage-dependent calcium channel potentiator.
J Appl Physiol
60:
942-948,
1986
67.
Tucker, A,
McMurtry IF,
Grover RF,
and
Reeves JT.
Attenuation of hypoxic pulmonary vasoconstriction by verapamil in intact dogs.
Proc Soc Exp Biol Med
151:
611-614,
1976[Abstract].
68.
Tucker, A,
and
Reeves JT.
Nonsustained pulmonary vasoconstriction during acute hypoxia in anesthetized dogs.
Am J Physiol
228:
756-761,
1975[ISI][Medline].
69.
Turner, JL,
and
Kozlowski RZ.
Relationship between membrane potential, delayed rectifier K+ currents and hypoxia in rat pulmonary arterial myocytes.
Exp Physiol
82:
629-645,
1997[Abstract].
70.
Vadula, MS,
Kleinman JG,
and
Madden JA.
Effect of hypoxia and norepinephrine on cytoplasmic free Ca2+ in pulmonary and cerebral arterial myocytes.
Am J Physiol Lung Cell Mol Physiol
265:
L591-L597,
1993
71.
Wang, Y,
Coe Y,
Toyoda O,
and
Coceani F.
Involvement of endothelin-1 in hypoxic pulmonary vasoconstriction in the lamb.
J Physiol (Lond)
482:
421-434,
1995[Abstract].
72.
Ward, JP,
and
Robertson TP.
The role of the endothelium in hypoxic pulmonary vasoconstriction.
Exp Physiol
80:
793-801,
1995[Abstract].
73.
Weir, EK,
and
Archer SL.
The mechanism of acute hypoxic pulmonary vasoconstriction: the tale of two channels.
FASEB J
9:
183-189,
1995
74.
Weir, EK,
McMurtry IF,
Tucker A,
Reeves JT,
and
Grover RF.
Prostaglandin synthetase inhibitors do not decrease hypoxic pulmonary vasoconstriction.
J Appl Physiol
41:
714-718,
1976
75.
Westcott, JY,
Henson J,
McMurtry IF,
and
O'Brien RF.
Uptake and metabolism of endothelin in the isolated perfused rat lung.
Exp Lung Res
16:
521-532,
1990[ISI][Medline].
76.
Wiener, CM,
Dunn A,
and
Sylvester JT.
ATP-dependent K+ channels modulate vasoconstrictor responses to severe hypoxia in isolated ferret lungs.
J Clin Invest
88:
500-504,
1991[ISI][Medline].
77.
Wiener, CM,
and
Sylvester JT.
Effects of glucose on hypoxic vasoconstriction in isolated ferret lungs.
J Appl Physiol
70:
439-446,
1991
78.
Willette, RN,
Ohlstein EH,
Mitchell MP,
Sauermelch CF,
Beck GR,
Luttmann MA,
and
Hay DW.
Nonpeptide endothelin receptor antagonists. VIII: attenuation of acute hypoxia-induced pulmonary hypertension in the dog.
J Pharmacol Exp Ther
280:
695-701,
1997
79.
Wolin, MS.
Reactive oxygen species and vascular signal transduction mechanisms.
Microcirculation
3:
1-17,
1996[Medline].
80.
Wong, J,
Vanderford PA,
Fineman JR,
Chang R,
and
Soifer SJ.
Endothelin-1 produces pulmonary vasodilation in the intact newborn lamb.
Am J Physiol Heart Circ Physiol
265:
H1318-H1325,
1993
81.
Wong, J,
Vanderford PA,
Winters JW,
Chang R,
Soifer SJ,
and
Fineman JR.
Endothelin-1 does not mediate acute hypoxic pulmonary vasoconstriction in the intact newborn lamb.
J Cardiovasc Pharmacol
22, Suppl8:
S262-S266,
1993[ISI][Medline].
82.
Yuan, XJ,
Goldman WF,
Tod ML,
Rubin LJ,
and
Blaustein MP.
Hypoxia reduces potassium currents in cultured rat pulmonary but not mesenteric arterial myocytes.
Am J Physiol Lung Cell Mol Physiol
264:
L116-L123,
1993