Department of Medicine, The Johns Hopkins University, Baltimore, Maryland 21205
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Hypoxia (0%
O2) evokes a late-phase,
endothelium-dependent contractile response in porcine isolated
pulmonary arteries that may be caused by a cyclooxygenase-independent,
endothelium-derived contractile factor. The aim of this study was to
further analyze the mechanism underlying this hypoxic response.
Proximal porcine pulmonary arterial rings were suspended for isometric
tension recording in organ chambers. Hypoxia (0%
O2) caused a late-phase, endothelium-dependent contractile response that was not inhibited by
the endothelin (ET)A-receptor
antagonist BQ-123 (106 M),
by the ETB-receptor antagonist
BQ-788 (10
7 M), or by their
combination. In contrast, ET-1 caused a concentration-dependent contraction of arterial rings that was inhibited by BQ-123
(10
6 M) and a relaxation
that was abolished by BQ-788
(10
7 M) or by endothelial
cell removal. Therefore, the endothelium-dependent contraction to
hypoxia is not mediated by ET. Hypoxia caused only relaxation in
endothelium-denuded rings. However, when a pulmonary valve leaflet, a
rich source of pulmonary endothelial cells, was placed into the lumen
of endothelium-denuded rings, hypoxia caused a late-phase contractile
response that was similar to that observed in arterial rings with
native endothelium. This hypoxic contraction persisted in the presence
of indomethacin (10
5 M) and
N-nitro-L-arginine
methyl ester (3 × 10
5
M) to block cyclooxygenase and nitric oxide synthase, respectively. These results suggest that hypoxic contraction of pulmonary arteries is
mediated by a diffusible, contractile factor released from hypoxic
endothelial cells. This contractile mediator is distinct from ET.
endothelium; hypoxia; endothelinA receptor; endothelinB receptor; pulmonary valve leaflet; pulmonary artery; endothelium-derived contractile factor
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
THE ROLE OF ENDOTHELIUM in mediating or modulating hypoxic pulmonary vasoconstriction has not been clearly defined. Hypoxia causes an immediate, transient contraction of isolated pulmonary and systemic arteries that is endothelium dependent and mediated by inhibition of the basal activity of the endothelium-derived dilator nitric oxide (NO) (11, 13, 17, 21, 30). Hypoxic constriction in the intact pulmonary circulation does not involve this mechanism (2, 5), which might suggest that the constriction is endothelium independent. Indeed, hypoxia can cause a direct contraction of isolated vascular smooth muscle cells (23, 25), presumably by inhibiting K+ currents (27, 40). Although modulation of endothelium-derived dilators may not mediate hypoxic pulmonary constriction, altered activity of endothelium-derived constrictor mediators may play an important role in initiating or amplifying smooth muscle constriction in response to hypoxia. Kovitz et al. (21) observed a late-phase, endothelium-dependent contraction to hypoxia in porcine isolated arteries that is not mediated by inhibition of dilator mediators. On the basis of, in part, a theoretical analysis, Kovitz et al. concluded that this hypoxic contraction was mediated by an endothelium-derived contractile factor (EDCF). A similar mechanism was proposed for a late-phase hypoxic contraction in rat isolated pulmonary arteries (22). Previous studies have suggested that the EDCF endothelin (ET) may play a role in hypoxic pulmonary vasoconstriction: 1) production of ET can increase during hypoxia (20) and 2) inhibition of ET receptors can attenuate hypoxic vasoconstriction in the intact pulmonary circulation (4, 6, 8, 26). However, this proposal remains controversial (9, 16, 38). The aim of the present study was to further analyze the mechanism underlying the late-phase hypoxic contraction and to determine whether the mediator was ET.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Blood Vessel Preparation
Male pigs (~25 kg) were anesthetized with ketamine (700 mg im) followed by pentobarbital sodium (12.5 mg/kg iv). The pigs were then killed by exsanguination through the femoral arteries. Proximal pulmonary arteries (8- to 12-mm ID) were isolated and cleared of adherent connective tissue (21). Rings were obtained by dividing the vessel into 5-mm-long segments. In some rings, the endothelium was removed by gently rubbing the intimal surface with a cotton swab and was confirmed during the course of each experiment by the loss of a relaxant response to acetylcholine (10Experimental Protocols
Role of ET. To analyze the influence of ET-receptor antagonists on the responses to ET or hypoxia, the rings were incubated for 30 min in the presence and absence of BQ-123 (10Responses to hypoxia were evaluated as previously described (21). During contraction of the arteries with phenylephrine (to 50% of KCl maximum), O2 tension was decreased in a stepwise fashion from 16 to 10, 4, and 0%. The level of O2 was decreased once the response to the previous level had stabilized. Responses to hypoxia were also evaluated as an abrupt change from 16 to 0% O2. At 16% O2, PO2 was 120-127 mmHg; at 10% O2, PO2 was 77-81 mmHg; at 4% O2, PO2 was 40-43 mmHg; and at 0% O2, PO2 was 8-12 mmHg.
Transfer experiments. To determine whether the hypoxic mediator was a diffusible mediator, transfer experiments were performed with pulmonary valve leaflets as a source of endothelial cells. Valve leaflets were dissected from the pulmonary outflow tract and stored at 4°C in a control solution until required in the experimental protocol. A concentration response to phenylephrine was determined in endothelium-denuded and endothelium-containing arterial rings. The phenylephrine was removed from the chambers, and the tension of the rings was allowed to return to baseline. The passive tension (5 g) was then relaxed by 2 g, the organ baths were lowered, and a pulmonary valve leaflet was carefully placed inside the endothelium-denuded arterial rings (Fig. 1). Control rings were treated in the same manner except no leaflet was inserted. The organ chambers were raised, and the passive tension was returned to 5 g. Arterial rings were then contracted to the 50% effective dose level of tension with phenylephrine and exposed to hypoxia. Pulmonary valves and arteries were obtained from the same animals.
|
The influence of valve placement on the reactivity of pulmonary arterial rings to phenylephrine was also determined in separate experiments. Concentration-response curves to phenylephrine were generated before and after placement of valve leaflets. In some experiments, valve leaflets were first incubated in distilled water (4°C for 4 h) to damage the endothelium and to determine the stearic effects of the valve on vascular reactivity.
Drugs and Solutions
Acetylcholine, N-nitro-L-arginine methyl ester (L-NAME), and phenylephrine hydrochloride were obtained from Sigma. Bradykinin was obtained from Calbiochem. BQ-123 and BQ-788 were obtained from American Peptide, and ET-1 was obtained from Peninsula Laboratories. The drugs were dissolved in distilled water and kept on ice during the course of the experiment except for ET and bradykinin, which were dissolved in acetic acid followed by dilution in distilled water (final chamber concentration of acetic acid was 0.001% vol/vol); BQ-123, which was dissolved in dimethyl sulfoxide followed by dilution in distilled water (final chamber concentration of dimethyl sulfoxide was 0.01% vol/vol); and BQ-788, which was dissolved in methanol followed by dilution in distilled water (final chamber concentration of methanol was 0.04% vol/vol). These concentrations of solvents had no effect on the hypoxic reactivity or the responses to constrictor or dilator agonists. All chemicals were the highest purity available. Stock solutions were prepared each day. All concentrations are expressed as the final molar concentration in the organ chamber.Data Analysis
Results are expressed as means ± SE. Concentration-response curves to ET determined under quiescent conditions are expressed as a percentage of the maximum response to KCl. Responses to ET or hypoxia determined during contraction to phenylephrine are expressed as a percentage of the precontraction. To compare concentration-response curves to ET, the effective concentration of agonist causing X% of the maximal contraction to KCl (ECX,KCl) was determined by regression analysis of the concentration-effect curves. Antagonist dissociation constants (KB) were determined with the formula KB = [B]/(CR ![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Responses to ET-1
Under quiescent conditions, ET-1 caused a concentration-dependent contraction of pulmonary arterial rings with endothelium. Endothelium removal increased the response to ET-1, causing an upward shift in the concentration-effect curve (Fig. 2).
|
The response to ET-1 was inhibited by the
ETA-receptor antagonist BQ-123
(106 M), which caused a
rightward shift of the concentration-effect curve with no change in the
maximum response in rings with and without endothelium (Fig. 2). The
log KB for
BQ-123 calculated at the EC50,KCl
level was 6.99 ± 0.18 in endothelium-denuded rings (n = 5 animals). In
endothelium-denuded rings, contractions with ET-1 were not
significantly influenced by the
ETB-receptor antagonist BQ-788 (3 × 10
7 M) either in
the presence or absence of BQ-123
(10
6 M; Fig. 2). However,
in endothelium-intact arterial rings, the addition of BQ-788 (3 × 10
7 M) significantly
enhanced the response to ET in both the presence and absence of BQ-123
(10
6 M).
In arterial rings with endothelium that were contracted with
phenylephrine, ET-1 (3 × 109 M) caused a biphasic
response consisting of an initial relaxation followed by a sustained
contraction (Fig. 3). The relaxation was abolished by the ETB-receptor
antagonist BQ-788 (3 × 10
7 M) or by removal of the
endothelium. The contraction with ET was increased by BQ-788 (3 × 10
7 M) or by endothelium
removal and was abolished by the
ETA-receptor antagonist BQ-123
(10
6 M). BQ-788
(3 × 10
7 M) had no
effect on the response to ET in endothelium-denuded rings (Fig. 3).
|
Effect of ET-Receptor Antagonists on Responses to Hypoxia
During a contraction with phenylephrine (50% maximal response), moderate hypoxia (10-4% O2) caused a graded relaxation that was similar in rings with and without endothelium. Severe hypoxia (0% O2) caused a transient increase followed by a slowly developing and sustained increase in tension in endothelium-containing rings but no significant change in tension in denuded rings (Fig. 4). The ET-receptor antagonists BQ-123 (10
|
Transfer of Endothelial Mediators From Pulmonary Valve Leaflets
During contraction with phenylephrine (to 50% of maximal response), bradykinin (10
|
As previously demonstrated (21), abrupt exposure to severe hypoxia (16-0% O2) caused relaxation of endothelium-denuded rings contracted with phenylephrine (to 50% of maximal response; Fig. 5). However, the presence of a pulmonary valve leaflet in endothelium-denuded rings converted this response into a slowly developing sustained contractile response (Fig. 5). This response was similar to the endothelium-dependent response observed in pulmonary arteries with native endothelial cells (21).
In arterial rings without endothelium contracted with phenylephrine (to
50% of maximal response), moderate hypoxia (10-4% O2) caused a graded relaxation,
and severe hypoxia (0% O2)
caused no further significant change in tension (Fig.
6). Placement of a pulmonary valve leaflet
in endothelium-denuded rings did not alter the response of the arterial
ring to moderate hypoxia (10-4% O2) but uncovered a late-phase
contraction to severe hypoxia (0% O2; Fig. 6). The magnitude of this
valve-dependent, late-phase hypoxic contraction was the same as that
observed in rings with native endothelium. This valve-dependent
contraction was still observed in the presence of indomethacin
(105 M) and
L-NAME (3 × 10
5 M) to inhibit
cyclooxygenase and NO synthase, respectively (Fig. 6).
|
The placement of a pulmonary valve leaflet in the lumen of an
endothelium-denuded ring depressed contractile responses to phenylephrine, causing a parallel rightward shift in the
concentration-response curve without affecting the maximum response
(Fig. 7). The inhibitory effect of the
valve was not influenced by
L-NAME (3 × 105 M) + indomethacin
(10
5 M) or by prior
incubation of the valve leaflet in distilled water (4°C for 4 h;
Fig. 7).
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In porcine isolated pulmonary arteries, severe hypoxia (0% O2) evokes a late-phase, endothelium-dependent contractile response that is not mediated by inhibition of dilator mediators (21). On the basis of, in part, a theoretical analysis, Kovitz et al. (21) suggested that this hypoxic contraction was mediated by a cyclooxygenase-independent EDCF. In the present study, the EDCF ET-1 caused contraction of the proximal porcine pulmonary artery by stimulating smooth muscle ETA receptors and relaxation by stimulating endothelial ETB receptors. However, inhibition of the ETA receptor (and/or the ETB receptor) did not inhibit the late-phase, endothelium-dependent contraction to hypoxia (0% O2). A pulmonary valve leaflet, used as a source of endothelial cells, restored the hypoxic contraction to endothelium-denuded rings. Our results suggest, therefore, that the late-phase, endothelium-dependent hypoxic constriction is mediated by a diffusible EDCF distinct from ET.
ET-1, -2, and -3 are synthesized by many different cell types, although ET-1 appears to be produced exclusively by endothelial cells (1, 39). There are also three known ET receptors, two of which (ETA and ETB) have been cloned with ~60% homology. ETA and ETB receptors are located on vascular smooth muscle and mediate contraction (1, 33, 36), whereas ETB receptors are also located on endothelial cells mediating relaxation via increased NO and/or prostacyclin production (12, 31). A putative ETC receptor, selective for ET-3, has been cloned (18) and may contribute to vascular smooth muscle contraction. Hypoxia has been demonstrated to increase ET production in isolated resistance arteries (28) and intact lungs (34) and may (20) or may not (24) increase ET-1 production from cultured endothelial cells. There has generally been agreement that ET-receptor antagonists attenuate the pulmonary hypertension and vascular remodeling associated with chronic hypoxia (4, 6, 8). However, the role of ET in acute hypoxic vasoconstriction is controversial. The ETA-receptor antagonist BQ-123 attenuated acute hypoxic vasoconstriction in an in vivo rat study (26), although this has not been a consistent finding. In isolated canine or rat arteries, blockade of ETA receptors with BQ-123 did not alter the contractile response to hypoxia (9, 16, 38). However, these and other studies of isolated arteries have focused on immediate and transient endothelium-dependent contractions to hypoxia that are mediated by inhibition of dilator mediators rather than by the release of an EDCF. Our in vitro model of hypoxic constriction, which appears to be mediated by an EDCF, is therefore a novel model to evaluate a role for ET in hypoxic pulmonary constriction.
Our results demonstrate, in the proximal porcine pulmonary artery, that
ET-1-induced contraction was inhibited by BQ-123, with a
KB (100 nM)
consistent with antagonism of ETA
receptors (3, 14). ET-1 also caused a relaxation that was abolished by
endothelial removal and by BQ-788, a selective
ETB-receptor antagonist (15).
Therefore, in the proximal porcine pulmonary artery, ET-1 mediates
contraction via the ETA receptor
on the smooth muscle and relaxation via endothelial
ETB receptors (35). Despite their
potency at inhibiting contractile responses to ET-1, the ET-receptor
antagonists did not inhibit the endothelium-dependent, late-phase
hypoxic contraction in the proximal pulmonary artery, implying that ET
does not play a role in mediating this response. However, it is
possible that hypoxia augmented the activity of a distinct ET receptor
on vascular smooth muscle that was not inhibited by these antagonists
(e.g., ETC). Indeed, BQ-123
caused a nonparallel shift in the ET-1 concentration-response curve, being more potent at low compared with high levels of tension. For
example, in endothelium-denuded rings, BQ-123 caused a significantly greater shift in the curve at the
EC30,KCl level compared with the
EC100,KCl level of tension
[log shifts in the concentration-response curve of 1.3 ± 0.2 (20-fold shift) and 0.55 ± 0.14 (3.5-fold shift), respectively;
P < 0.05;
n = 5 rings].
(EC30,KCl and
EC100,KCl levels are equivalent to
~20 and 70%, respectively, of the maximal response to ET-1.) This
pattern was not influenced by blockade of
ETB receptors (BQ-788) and may
therefore reflect ET-1-induced activation of a
non-ETA,
non-ETB receptor of low activity
(e.g., ETC) (10). However, ET-1
(3 × 109 M), when
given to endothelium-denuded rings during anoxia (0% O2), caused a contraction that
was still abolished by the
ETA-receptor antagonist BQ-123
(10
6 M; data not shown).
These results indicate that hypoxia does not uncover a novel ET
receptor and that ET-1 does not mediate the late-phase,
endothelium-dependent contraction to hypoxia.
To further characterize the nature of the hypoxic mediator, transfer experiments were performed with pulmonary valve leaflets as a source of endothelial cells. Although endothelium-denuded pulmonary arterial rings normally relax in response to hypoxia, the presence of a valve leaflet in endothelium-denuded rings restored the endothelium-dependent contraction to severe hypoxia (0% O2). The contraction persisted after L-NAME and indomethacin, confirming that the contraction was not mediated by inhibition of endothelial dilator mediators but rather indicated the release of a diffusible contractile factor by the endothelium. Placing the leaflet into an endothelium-denuded ring caused a rightward shift in the phenylephrine concentration-effect curve that was unaffected by L-NAME and indomethacin or by pretreatment of the valve with distilled water. This suggests that the leaflet does not release significant amounts of dilator mediators under basal conditions but that it does exert a slight mechanical effect on arterial contractility. Indeed, although the presence of the valve in endothelium-denuded arteries restored the late endothelium-dependent contractile response, it did not restore the initial, transient endothelium-dependent contraction to moderate hypoxia (21) (Fig. 6). This transient response is mediated by hypoxic inhibition of the basal activity of endothelium-derived NO (21).
The role of endothelium in mediating or modulating hypoxic pulmonary vasoconstriction in vivo has not been clearly defined. Hypoxia has been demonstrated to directly produce contraction in cultured pulmonary arterial smooth cells in the absence of endothelium (25). Hypoxia may initially increase intracellular Ca2+ through the release of stores in the sarcoplasmic reticulum or by directly inhibiting the delayed rectifier K+ channels in smooth muscle cells, leading to depolarization, opening of voltage-operated Ca2+ channels, and the influx of extracellular Ca2+ (27, 40). The Ca2+ influx may stimulate further sustained increases in intracellular Ca2+ via Ca2+-induced Ca2+ release from internal stores, resulting in smooth muscle contraction (7, 27, 40). The endothelium, by releasing a contractile factor, may amplify this response (29). The mechanisms controlling the activity of this hypoxic mediator were not investigated in the present study. The mediator could be released in response to hypoxia (20, 21) or it could be released continuously, with hypoxia modulating its activity on the vascular smooth muscle. The late-phase, endothelium-dependent contraction to hypoxia was observed in pulmonary but not in systemic arteries. Isolated porcine iliac arteries (n = 6) exposed to anoxia for 45 min relaxed by 97 ± 3% of the phenylephrine contraction. This is in keeping with previous findings in isolated rat systemic arteries (22). Differences in the activity of this factor may therefore contribute to the heterogeneous effects of hypoxia in the pulmonary and systemic circulations and to pathophysiological increases in pulmonary vascular resistance.
In summary, hypoxic pulmonary endothelial cells release a diffusible, cyclooxygenase-independent contractile factor that mediates hypoxic constriction in isolated pulmonary arteries. This factor is distinct from ET. The nature of the factor and the mechanisms controlling its activity remain to be determined.
![]() |
ACKNOWLEDGEMENTS |
---|
This study was supported by National Heart, Lung, and Blood Institute Grant HL-09385-01 to S. P. Gaine.
![]() |
FOOTNOTES |
---|
Present address of S. P. Gaine: Dept. of Medicine, University of Maryland, Baltimore, MD 21201.
Present address of and address for reprint requests: N. A. Flavahan, Heart and Lung Institute, The Ohio State Univ., 524 Medical Research Facility, 420 West 12th Ave., Columbus, OH 43210-1214.
Received 23 June 1997; accepted in final form 30 December 1997.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Arai, H.,
S. Hori,
I. Aramori,
H. Ohkubo,
and
J. Nakanishi.
Cloning and expression of a cDNA encoding an endothelin receptor.
Nature
348:
730-732,
1990[Medline].
2.
Archer, S. L.,
J. P. Tolins,
L. Raij,
and
E. K. Weir.
Hypoxic pulmonary vasoconstriction is enhanced by inhibition of the synthesis of an endothelium derived relaxing factor.
Biochem. Biophys. Res. Commun.
164:
1198-1205,
1989[Medline].
3.
Bax, W. A.,
and
P. R. Saxena.
The current endothelin receptor classification: time for reconsideration?
Trends Pharmacol. Sci.
15:
379-386,
1994[Medline].
4.
Bonvallet, S. T.,
M. R. Zamora,
K. Hasunuma,
K. Sato,
N. Hanasato,
D. Anderson,
K. Sato,
and
T. J. Stelzner.
BQ123, an ETA-receptor antagonist, attenuates hypoxic pulmonary hypertension in rats.
Am. J. Physiol.
266 (Heart Circ. Physiol. 35):
H1327-H1331,
1994
5.
Brashers, V. L.,
M. J. Peach,
and
C. E. Rose.
Augmentation of hypoxic pulmonary vasoconstriction in the isolated perfused rat lung by in vitro antagonists of endothelium-dependent relaxation.
J. Clin. Invest.
82:
1495-1502,
1988[Medline].
6.
Chen, S. J.,
Y. F. Chen,
Q. C. Meng,
J. Durand,
V. S. Dicarlo,
and
S. Oparil.
Endothelin-receptor antagonist bosentan prevents and reverses hypoxic pulmonary hypertension in rats.
J. Appl. Physiol.
79:
2122-2131,
1995
7.
Cornfield, D. N.,
T. Stevens,
I. F. McMurtry,
S. H. Abman,
and
D. M. Rodman.
Acute hypoxia causes membrane depolarization and calcium influx in fetal pulmonary artery smooth muscle cells.
Am. J. Physiol.
266 (Lung Cell. Mol. Physiol. 10):
L469-L475,
1994
8.
DiCarlo, V. S.,
S. J. Chen,
Q. C. Meng,
J. Durand,
M. Yano,
Y. F. Chen,
and
S. Oparil.
ETA-receptor antagonist prevents and reverses chronic hypoxia-induced pulmonary hypertension in rat.
Am. J. Physiol.
269 (Lung Cell. Mol. Physiol. 13):
L690-L697,
1995
9.
Douglas, S. A.,
L. M. Vickery-Clark,
and
E. H. Ohlstein.
Endothelin-1 does not mediate hypoxic vasoconstriction in canine isolated blood vessels: effect of BQ-123.
Br. J. Pharmacol.
108:
418-421,
1993[Medline].
10.
Flavahan, N. A.,
T. J. Rimele,
J. P. Cooke,
and
P. M. Vanhoutte.
Characterization of the postjunctional alpha1- and alpha2-adrenoceptors activated by exogenous and nerve-released norepinephrine in the canine saphenous vein.
J. Pharmacol. Exp. Ther.
230:
699-705,
1984[Abstract].
11.
Graser, T.,
and
P. M. Vanhoutte.
Hypoxic contraction of canine coronary arteries: role of endothelium and cGMP.
Am. J. Physiol
261 (Heart Circ. Physiol. 30):
H1769-H1777,
1991
12.
Hirata, Y.,
T. Emori,
S. Eguchi,
K. Kanno,
T. Imai,
K. Ohta,
and
F. Marumo.
Endothelin receptor subtype B mediates synthesis of nitric oxide by cultured bovine endothelial cells.
J. Clin. Invest.
91:
1367-1373,
1993[Medline].
13.
Holden, W. E.,
and
E. McCall.
Hypoxia-induced contractions of porcine pulmonary artery strips depend on intact endothelium.
Exp. Lung Res.
7:
101-112,
1984[Medline].
14.
Ihara, M.,
K. Ishikawa,
T. Fukoroda,
T. Saeki,
K. Funabashi,
T. Fukami,
H. Suda,
and
M. Yano.
In vitro biological profile of a highly potent novel endothelin (ET) antagonist BQ-123 selective for the ETA receptor.
J. Cardiovasc. Pharmacol.
12:
S11-S14,
1992.
15.
Ishikawa, K.,
M. Ihara,
K. Noguchi,
T. Mase,
N. Mino,
T. Saeki,
T. Fukuroda,
T. Fukami,
S. Ozaki,
T. Nagase,
Biochemical and pharmacological profile of a potent and selective endothelin B-receptor antagonist, BQ-788.
Proc. Natl. Acad. Sci. USA
91:
4892-4896,
1994[Abstract].
16.
Ishizaki, T.,
T. Higashi,
K. Shigemori,
M. Takeoka,
T. Nakai,
S. Miyabo,
and
N. F. Voelkel.
Endogenous ETA receptors do not modulate acute hypoxic vasoconstriction.
Appl. Cardiopulm. Pathophysiol.
5:
153-159,
1995.
17.
Johns, R. A.,
J. M. Linden,
and
M. J. Peach.
Endothelium-dependent relaxation and cyclic GMP accumulation in rabbit pulmonary artery are selectively impaired by moderate hypoxia.
Circ. Res.
65:
1508-1515,
1989[Abstract].
18.
Karne, S.,
C. K. Jayawickreme,
and
M. R. Lerner.
Cloning and characterization of an endothelin-3 specific receptor (ETC receptor) from Xenopus laevis dermal melanophores.
J. Biol. Chem.
268:
19126-19133,
1993
19.
Kenakin, T.
Pharmacologic Analysis of Drug Receptor Interaction. New York: Raven, 1993.
20.
Kourembanas, S.,
P. A. Marsden,
L. P. McQuillan,
and
D. V. Faller.
Hypoxia induces endothelin gene expression and secretion in cultured human endothelium.
J. Clin. Invest.
88:
1054-1057,
1991[Medline].
21.
Kovitz, K. L.,
T. D. Aleskowitch,
J. T. Sylvester,
and
N. A. Flavahan.
Endothelium-derived contracting and relaxing factors contribute to hypoxic responses of pulmonary arteries.
Am. J. Physiol.
265 (Heart Circ. Physiol. 34):
H1139-H1148,
1993
22.
Leach, R. M.,
T. P. Robertson,
C. H. C. Twort,
and
J. P. Ward.
Hypoxic vasoconstriction in rat pulmonary and mesenteric arteries.
Am. J. Physiol.
266 (Lung Cell. Mol. Physiol. 10):
L223-L231,
1994
23.
Madden, J. A.,
M. S. Vadula,
and
V. P. Kurup.
Effects of hypoxia and other vasoactive agents on pulmonary and cerebral artery smooth muscle cells.
Am. J. Physiol.
263 (Lung Cell. Mol. Physiol. 7):
L384-L393,
1992
24.
Markewitz, B. A.,
D. E. Kohan,
and
J. R. Michael.
Hypoxia decreases endothelin-1 synthesis by rat lung endothelial cells.
Am. J. Physiol.
269 (Lung Cell. Mol. Physiol. 13):
L215-L220,
1995
25.
Murray, T. R.,
L. Chen,
B. E. Marshall,
and
E. J. Macarak.
Hypoxic contraction of cultured pulmonary vascular smooth muscle cells.
Am. J. Respir. Cell Mol. Biol.
3:
457-465,
1990[Medline].
26.
Oparil, S.,
S. J. Chen,
Q. C. Meng,
T. S. Elton,
M. Yano,
and
Y. F. Chen.
Endothelin-A receptor antagonist prevents acute hypoxia-induced pulmonary hypertension in the rat.
Am. J. Physiol.
268 (Lung Cell. Mol. Physiol. 12):
L95-L100,
1995
27.
Post, J. M.,
J. R. Hume,
S. L. Archer,
and
E. K. Weir.
Direct role for potassium channel inhibition in hypoxic pulmonary vasoconstriction.
Am. J. Physiol.
262 (Cell Physiol. 31):
C882-C890,
1992
28.
Rakugi, H.,
Y. Tabuchi,
M. Nakamaru,
M. Nagano,
K. Higashimori,
H. Mikami,
T. Ogihara,
and
N. Suzuki.
Evidence for endothelin-1 release from resistance vessels of rats in response to hypoxia.
Biochem. Biophys. Res. Commun.
169:
973-977,
1990[Medline].
29.
Robertson, T. P.,
P. I. Aaronson,
and
J. P. Ward.
Hypoxic vasoconstriction and intracellular Ca2+ in pulmonary arteries: evidence for PKC-independent Ca2+ sensitization.
Am. J. Physiol.
268 (Heart Circ. Physiol. 37):
H301-H307,
1995
30.
Rubanyi, G. M.,
and
P. M. Vanhoutte.
Hypoxia releases a vasoconstrictor substance from the canine vascular endothelium.
J. Physiol. (Lond.)
364:
45-56,
1985[Abstract].
31.
Sakuri, T.,
M. Yanagisawa,
Y. Takuwa,
H. Miyazaki,
S. Kimura,
K. Goto,
and
T. Masaki.
Cloning of a cDNA encoding a non-isopeptide selective subtype of the endothelin receptor.
Nature
348:
732-735,
1990[Medline].
32.
Salvaterra, C. G.,
and
W. F. Goldman.
Acute hypoxia increases cytosolic calcium in cultured pulmonary arterial myocytes.
Am. J. Physiol.
264 (Lung Cell. Mol. Physiol. 8):
L323-L328,
1993
33.
Shetty, S. S.,
T. Okada,
R. L. Webb,
D. DelGrande,
and
R. W. Lappe.
Functionally distinct endothelin B receptors in vascular endothelium and smooth muscle.
Biochem. Biophys. Res. Commun.
191:
459-464,
1993[Medline].
34.
Shirakami, G.,
K. Nakao,
Y. Saito,
T. Magaribuchi,
M. Jougasaki,
M. Mukoyama,
H. Arai,
K. Hosoda,
S. Suga,
Y. Ogawa,
Acute pulmonary alveolar hypoxia increases lung and plasma endothelin-1 levels in conscious rats.
Life Sci.
48:
969-976,
1991[Medline].
35.
Sudjarwo, S. A.,
M. Hori,
M. Takai,
Y. Urade,
T. Okada,
and
H. Karaki.
A novel subtype of endothelin B receptor mediating contraction in swine pulmonary vein.
Life Sci.
53:
431-437,
1993[Medline].
36.
Sumner, M. J.,
T. R. Cannon,
J. W. Mundin,
D. G. White,
and
I. S. Watts.
Endothelin ETA and ETB receptors mediate vascular smooth muscle contraction.
Br. J. Pharmacol.
107:
858-860,
1992[Abstract].
37.
Takeoka, M.,
T. Ishizaki,
A. Sakai,
S. W. Chang,
K. Shigemori,
T. Higashi,
and
G. Ueda.
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[Medline].
38.
Wong, J., P. A. Vanderford, J. W. Winters, R. Chang, S. J. Soifer, and J. R. Fineman.
Endothelin-1 does not mediate acute hypoxic pulmonary
vasoconstriction in the intact newborn lamb. J. Cardiovasc. Pharmacol. 22, Suppl. 8: S262-S266, 1993.
39.
Yanagisawa, M.,
H. Kurihara,
S. Kimura,
Y. Tomobe,
M. Kobayashi,
Y. Mitsui,
Y. Yazaki,
K. Goto,
and
T. Masaki.
A novel potent vasoconstrictor peptide produced by vascular endothelial cells.
Nature
332:
411-415,
1988[Medline].
40.
Yuan, X.,
W. F. Goldman,
M. L. Tod,
L. J. Rubin,
and
M. P. Blaustein.
Hypoxia reduces potassium currents in cultured rat pulmonary but not mesenteric arterial myocytes.
Am. J. Physiol.
264 (Lung Cell. Mol. Physiol. 8):
L116-L123,
1993