Thromboxane synthase and TP receptor mRNA in rat kidney and brain: effects of salt intake and ANG II

Christopher S. Wilcox and William J. Welch

Division of Nephrology and Hypertension and Center for Hypertension and Renal Disease Research, Georgetown University Medical Center, Washington, DC 20007


    ABSTRACT
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

A TP receptor (TP-R) mimetic causes salt-sensitive hypertension and renal afferent arteriolar vasoconstriction. TP-Rs mediate effects of ANG II on renal vascular resistance and drinking. Therefore, we investigated the hypothesis that thromboxane A2 synthase (TxA2-S) and/or TP-R expression is regulated by salt and/or ANG II. Rats (n = 6) received high-salt (HS) or low-salt (LS) diets. Additional HS-diet rats received ANG II while other HS- and LS-diet rats received the AT1 receptor (AT1-R) antagonist losartan. Excretion of thromboxane B2 by conscious rats was increased with the HS diet compared with the LS diet (126 ± 10 vs. 48 ± 5 pmol/24 h, respectively; P < 0.01). The mRNA abundance for TP-Rs (relative to beta -actin) in the kidney cortex was enhanced 30% by the HS diet (P < 0.001) and was reduced 50% by the addition of ANG II (P < 0.001). However, during losartan administration, the effects of salt were reversed; mRNA more than doubled during the LS diet (P < 0.001). Similarly, the mRNA abundance for TP-Rs in the brain stem was reduced by 50% with the addition of ANG II (P < 0.001) and during losartan administration was almost doubled by the LS diet (P < 0.001). The mRNA abundance for TxA2-S in the kidney cortex also was increased many times with the HS diet (P < 0.001). In contrast, the mRNA for TxA2-S in the brain was unaffected by salt. ANG II did not affect TxA2-S at either site. During losartan administration, TxA2-S increased modestly in the brain stem with the LS diet. mRNA abundance for TP-Rs in the kidney cortex and brain stem is suppressed by ANG II acting on AT1-Rs. In the absence of AT1-Rs, expression of TP-Rs at both sites is enhanced by LS intake. In contrast, ANG II does not affect the mRNA abundance for TxA2-S. Expression of TxA2-S is enhanced by HS intake in the kidney cortex but by LS intake in the brain stem only during losartan administration. Thus TP-Rs are strongly dependent on ANG II acting on AT1-Rs, whereas TxA2-S is regulated differentially in the kidney cortex and brain stem by salt intake.

thromboxane A2; prostaglandins; angiotensin II; losartan; angiotensin receptor blocker; thromboxane prostanoid receptor


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

THROMBOXANE A2 (TXA2) IS GENERATED from PGH2 by TxA2 synthase (TxA2-S). TxA2-S is expressed in the kidney (53). TxA2, PGH2, and isoprostanes, such as 8-iso-PGF2alpha , and stable mimetics, such as U-46619, are agonists for the TP receptor (TP-R) (14, 17). TP-Rs are expressed in the blood vessels and in kidney microvessels, glomeruli, mesangial cells, thick ascending limbs (TALs) of the loops of Henle, and collecting ducts (1, 10, 11, 48).

Several lines of evidence suggest that TxA2-S and TP-Rs in the kidney are regulated by salt intake or ANG II. Thus hypertension in response to a prolonged infusion of U-46619 is enhanced by high-salt (HS) intake (55). U-46619 enhances the sympathetic nervous system of conscious rats (13) and the vasoconstrictive tubuloglomerular feedback (TGF) response of anesthetized rats. Both of these effects are enhanced by an HS diet (56). Moreover, the effects of U-46619 on TGF correlate with the abundance of the mRNA for TP-Rs in kidney and glomeruli of rats on different salt intakes. Thus the kidney is sensitive to TP-R activation, and this response is salt dependent. However, effects of salt on TxA2-S expression or on thromboxane B2 (TxB2) excretion are not clear.

The brain also generates TxA2 (6, 8, 44-47) and expresses TP-Rs (12, 34) on glial cells and astrocytes (12, 18, 34, 35). The intracerebroventricular administration of U-46619 increases blood pressure. This pathway also is sensitive to salt. Thus the increase in blood pressure with intracerebroventricular U-46619 is enhanced by HS intake (12). The drinking response to central ANG II is blunted by intracerebroventricular injection of a TP-R antagonist (19). A TP-R mimetic and ANG II, when given into the brain, synergize to promote drinking (19). Thus the brain-TP-R pathway apparently interacts with salt intake and ANG II, but the mechanism is unclear.

Vasoconstrictor PGs enhance many of the effects of ANG II. Thus blockade of TP-Rs, and in some studies blockade of TxA2-S, blunts or prevents the pressor response to infused ANG II (32, 33, 62), the development of renovascular hypertension in the two-kidney, one-clip Goldblatt or aortic coarctation models of renovascular hypertension in the rat (23, 59, 60), the increase in renal vascular resistance during ANG II infusion (24, 31, 62) and the dipsogenic response to intracerebroventricular ANG II infusion (19). These data implicate TxA2-S and/or TP-Rs in the renal and central nervous system actions of ANG II. Therefore, we investigated the hypothesis that dietary salt intake or ANG II regulate the mRNA abundance for TP-Rs and TxA2-S in the kidney cortex and brain stem.


    METHODS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Studies were undertaken on male Sprague-Dawley rats weighing 200-250 g. Animals were habituated in their cages to a standard rat chow (Na+ content 0.3 g/100 g; Ralston Purina) for 5 days before randomization. Thereafter, all rats were fed a regulated diet with identical composition except for the NaCl (Teklad, Madison, WI). The Na+ content of the HS diet was 3 g/100 g, and for the LS diet it was 0.03 g/100 g. The LS diet is sufficient for normal growth over an 8- to 10-day period. Rats were studied after 6 days on each protocol.

Protocols. Rats were studied according to the following protocols: 1) series A; group 1, HS intake (n = 6); group 2, LS intake (n = 6); and group 3, HS+ANG II intake (n = 6); and 2) series B; group 4, HS+losartan intake (n = 6); and group 5, LS+losartan intake (n = 6). Rats in series A and B were analyzed separately.

Before starting the 6 days of a regulated diet, animals in group 3 were anesthetized with pentobarbital sodium (50 mg/kg ip; Abbott Laboratories, North Chicago, IL) and fitted with a subcutaneous osmotic minipump (Alza, Palo Alto, CA) to deliver ANG II at 200 ng · kg-1 · min-1. In a prior series, our laboratory found that this protocol increased the mean arterial pressure from 107 to 129 mmHg and reduced the renal blood flow from 9.6 to 8.0 ml · min-1 · g-1 (9). Animals in series B were given losartan (1 mg/ml) in the drinking water.

Excretion of TxB2. Rats were studied on day 6 of LS or HS diets. They were accommodated for 1 day to metabolism cages, and for the next 24 h a urine sample was collected from the cage. Urine was collected into containers with streptomycin (2,000 IU), penicillin G (2,000 IU), and amphotericin B (5 µg) to prevent microbial growth. It was centrifuged, separated from sediment, and stored at -70°C until analyzed for TxB2. These rats were separate from those used for mRNA studies.

The details of the assay, including dual system purification by organic excretion and thin-layer chromatography, individual sample recovery, limits of detection, intra- and interassay coefficients of variation, cross-reactivity, and validation against gas chromatography mass spectroscopy, have been published (57).

Extraction and analysis of mRNA. For preparation of the kidney (56) and brain (12), groups of rats were anesthetized on day 6 of the protocol with thiobarbital (Inactin, 100 mg/kg ip; Research Biochemicals International, Natick, MA). The chest was opened, and the left ventricle was punctured to flush the organs with ice-cold 0.154 NaCl. The entire brain stem (dissected free from the cerebellum, midbrain, and cortex) and one kidney were removed, cleared of connective tissue, and placed in ice-cold saline solution. The kidney was cut longitudinally and a segment of cortex was removed. Total RNA was extracted by using RNA ATAT-60 (Tel-test B, Friendswood, TX). The mRNA was reverse transcribed with oligo(dT)16 as the primer and murine leukemia virus RT by using an RNA PCR kit (PerkinElmer, Branchburg, NJ). The primers used for PCR for the TP-R gene product were selected from the published cDNA sequences of the rat TP-R (GenBank accession no. D32080) (1). For TxA2-S, the sense was 5'-TTCCTGCAGATGGTGCTGGATG-3' and the antisense was 5'-AGGTATGTGATGAAGGAGAGCG-3' (235 bp) and TxA2-S (64) (GenBank accession no. D31798) (49) as described previously (12). For the TP-R, the sense was 5'- TGGACTGGCGTGCCACTGAT-3' and the antisense was 5'-AGCAAGGGCATCCAACACACCGTG-3' (502 bp). The primers for the TP-R were selected to amplify the alpha - and beta -isoforms of the receptor (30). beta -Actin was selected as the "housekeeper gene" for comparison, because beta -actin mRNA abundance in the rat kidney is independent of salt intake (56). The sense primer was 5'-GATCAAGATCATTGCTCCTC-3', and the antisense was 5'-TGTACAATCAAAGTCCTCAG-3' (426 bp). We detected no differences in beta -actin expression in the kidneys or brain stem in the different groups used in these protocols. Therefore, the amounts of TP-R and TxA2-S cDNAs were normalized by the amounts of beta -actin cDNA. The reaction mixture contained 50 pmol of each primer, 1.25 mM deoxynucleotide mixture, 2.5 µl Taq DNA polymerase, 10 mM Tris (pH 10), 50 mM KCl, and 1.5 mM MgCl2 and was carried out by the following protocol. After an initial melting temperature of 94°C for 4 min, there were 30 s of denaturation at 94°C, 45 s of annealing at 60°C, and 45 s of extension at 72°C for 7 min. The PCR product was analyzed on a 1.5% agarose gel stained with ethidium bromide and visualized under ultraviolet light. The size of the products was compared with rat kidney cDNA probes for TP-Rs (1) and TxA2-S (49), kindly provided by Dr. Kazu Takeuchi (Tokohu University, Sendai, Japan). To verify authenticity of the PCR products, amplified TP-R and TxA2-S cDNAs from the rat kidney cortex and brain stem were purified with Microcon (Amicon, Beverly, MA) and sequenced with an AmpliTaq cycle sequencing kit (PerkinElmer).

Care was taken to optimize conditions for the RT-PCR. For all products, pilot studies were undertaken with graded amounts of cDNA to ensure that product (as assessed by densitometry) increased log-linearly with the cDNA amount in the ranges tested. Negative controls were undertaken by PCR without prior RT and by RT-PCR of the buffer used.

Statistical analysis. The data were subjected to ANOVA to assess the effects of salt intake (group 1 vs. 2; series A) and ANG II (group 1 vs. 3; series A) and of salt intake during losartan administration (group 4 vs. 5; series B). Data are presented as means ± SE.

The studies were designed to test two a priori hypotheses. First, the expression of mRNA for TxA2-S or TP-Rs could be stimulated by ANG II independently of salt intake. This was refuted if there was no significant difference in mRNA abundance in a comparison of HS intake with HS+ANG II intake. Second, the expression of mRNA for TxA2-S or TP-Rs could be stimulated by salt intake independently of AT1 receptors (AT1-Rs). This was refuted if there was no significant difference between LS+losartan intake and HS+losartan intake.


    RESULTS
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

The 24-h excretion of TxB2 by conscious rats is shown in Fig. 1. It is apparent that excretion is increased significantly by 6 days of HS intake compared with LS intake.


View larger version (10K):
[in this window]
[in a new window]
 
Fig. 1.   Values are means ± SE and represent excretion of thromboxine B2 (TxB2) by conscious rats after 6 days of accommodation to a high-salt (HS) or low-salt (LS) diet.

The mRNA abundance for TP-Rs (relative to beta -actin) extracted from the kidney cortex and brain stem during HS, LS, and HS+ANG II intake are shown in Fig. 2. For the kidney but not the brain, HS intake enhanced the mRNA for TP-Rs by 30% (P < 0.001). For both the kidney and the brain, the abundance of TP-Rs during HS intake was reduced by ~50% by ANG II infusion (P < 0.001). We conclude that ANG II infusion inhibits mRNA for TP-Rs in the kidney cortex and brain stem independently of salt intake.


View larger version (20K):
[in this window]
[in a new window]
 
Fig. 2.   Values are means ± SE and represent mRNA abundance for TP receptors expressed as density relative to beta -actin comparing kidney cortex (A) with brain stem (B) in rats adapted to HS, LS, or HS+ANG II intake. ns, Not significant.

During losartan administration, LS intake led to a large increase in the mRNA for TP-Rs in the kidney cortex (2-fold) and brain stem (60%) (Fig. 3). Thus salt restriction stimulates TP-R expression in the kidney and brain independently of AT1-Rs.


View larger version (46K):
[in this window]
[in a new window]
 
Fig. 3.   Values are means ± SE and represent mRNA abundance for TP receptors expressed as density relative to beta -actin comparing kidney cortex (A) with brain stem (B) in rats adapted to HS and LS intake during losartan administration.

The mRNA abundance for TxA2-S (relative to beta -actin) in the kidney cortex and brain stem during HS, LS, and HS+ANG II intake is shown in Fig. 4. The TxA2-S abundance in the kidney was increased >20-fold during HS intake, whereas the abundance in the brain was not changed significantly. Unlike TP-Rs, there were no effects of ANG II during HS intake.


View larger version (23K):
[in this window]
[in a new window]
 
Fig. 4.   Values are means ± SE and represent mRNA abundance for thromboxine A2 synthase by conscious rats after 6 days of accommodation to an HS or LS diet expressed as density relative to beta -actin comparing kidney cortex (A) with brain stem (B) in rats adapted to HS, LS, or HS+ANG II intake.

During losartan administration, there was a similar effect of salt intake on TxA2-S in the kidney (Fig. 5) as seen in the absence of losartan (Fig. 4). However, during losartan administration there was an increase in mRNA for TxA2-S in the brain stem during LS intake of 60%. We conclude that salt intake has divergent effects on TxA2-S expression in the kidney and brain. Salt loading stimulates expression in the kidney, and salt restriction stimulates expression in the brain. These effects are largely independent of ANG II and AT1-Rs.


View larger version (43K):
[in this window]
[in a new window]
 
Fig. 5.   Values are means ± SE and represent mRNA abundance for thromboxine A2 synthase expressed as density relative to beta -actin comparing kidney cortex (A) with brain stem (B) in rats adapted to HS and LS during losartan administration.


    DISCUSSION
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

Our laboratory found previously that HS intake enhances mRNA abundance for TP-Rs in the kidney cortex and glomeruli (56). This was confirmed in the present study. The main new findings are that this effect of HS intake to increase mRNA abundance for TP-Rs is specific for the kidney because it is not found in the brain stem and is dependent on ANG II and AT1-Rs at both sites. Remarkably, during losartan administration, the increased TP-R expression in the kidneys seen during HS intake is reversed, and in both the kidney and the brain, TP-R expression is increased substantially by salt restriction when the effects of AT1-Rs are prevented by losartan. These data demonstrate that the prominent effect on TP-R expression in these protocols is suppression by ANG II acting on AT1-Rs. This action of ANG II apparently conceals an effect of salt restriction to enhance expression that is seen only during AT1-R blockade. Because ANG II levels diminish during HS intake and ANG II suppresses the expression of TP-Rs, the increase in TP-Rs in the kidneys with HS intake may be ascribed to a loss of the inhibitory effect of ANG II acting on AT1-Rs. Similar to TP-Rs, the mRNA abundance for TxA2-S also increases with HS intake in the kidney, although it is not changed in the brain. However, ANG II does not change the expression of TxA2-S in the kidney or brain. Moreover, the increase in TxA2-S with HS intake in the kidney and with LS intake in the brain persists during losartan administration. We conclude that the major determinant of TxA2-S expression is salt intake independent of ANG II and AT1-Rs. These data indicate the quite distinct effects of ANG II on the regulation of the mRNAs for TP-Rs and TxA2-S.

Rat glomeruli and mesangial cells contain high-affinity binding sites for TP-R ligands (10, 14). The distribution of TP-R protein within the kidney has been studied by immunocytochemistry. Receptors are located on arterial walls, microvessels, glomeruli, proximal tubules, TALs, distal tubules, and collecting ducts (4, 48). In situ hybridization studies have located the mRNA for TP-Rs in glomeruli, afferent and efferent arterioles, the luminal aspects of the TALs, macula densa cells, collecting ducts (1), and the renal medulla (27). Receptor-mediated contractile responses to TP-R activation have been shown in isolated glomerular mesangial cells and renal afferent arterioles (16, 25, 28, 43). A thromboxane mimetic enhances NaCl reabsorption in the loop of Henle and enhances the TGF responses (58). These data suggest that TP-Rs are distributed to renal microvessels, glomeruli, macula densa cells, and tubules of the kidney. TP-Rs also are expressed in the brain (3), where they are distributed to glial cells and astrocytes (12, 18, 34).

We considered two explanations for the reduction of TP-R expression by ANG II. First, this could represent ligand-associated receptor downregulation (39). ANG II stimulates phopholipases that substantially enhance PG formation in the kidney (26, 29). ANG II infusion increases renal excretion of TxB2, implying enhanced renal TxA2 generation (26). Indeed, blockade of TxA2-S or TP-Rs blunts the renal vasoconstriction with prolonged ANG II infusion (31, 62). An increase in vasoconstriction has been ascribed to PGH2, which also activates TP-Rs (22). Moreover, ANG II leads to oxidative stress and an enhanced excretion of 8-iso-PGF2alpha (41, 42). Thus all the identified ligands of the TP-R are generated in response to ANG II infusion. Ligand-associated downregulation of TP-Rs could account for the reduced expression of TP-Rs in the kidney during ANG II infusion and the enhancement during AT1-R blockade with losartan.

A second possible explanation derives from the evidence that losartan also blocks TP-Rs (7, 21). Therefore, the losartan-induced increase in mRNA for TP-Rs may represent upregulation of the receptor during pharmacological blockade. It is not clear how this could explain the large effects of salt intake on TP-R expression during losartan administration.

The protein for TxA2-S is expressed in renal microvessels, interstitial fibroblasts, and macrophages (36, 40), and in the distal nephron of the kidney (37). Isolated glomeruli and glomerular mesangial cells and podocytes release TxB2 and therefore presumably express TxA2-S (29). Microdissected nephron segments also release TxB2. The largest sites for release are glomeruli, TALs, and collecting ducts (2). Thus TxA2 can be widely synthesized in the kidney. In the brain, TxA2 is synthesized predominantly in glia (44, 45). Very large quantities of TxB2 are released from the brain in response to hypoperfusion or trauma (6, 8, 46). However, we are not aware that the regulation of TxA2-S in the kidney or brain has been studied directly.

The cause for the salt-dependent, but ANG II- and AT1-R-independent, increase in mRNA abundance for TxA2-S in the kidney is not clear. This is analogous to the salt-dependent, but ANG II- and AT1-R-independent, expression of mRNA and protein for nitric oxide synthase type I in the kidney cortex and macula densa cells (51, 52). It demonstrates that the kidney contains potentially unique mechanisms that would provide it with the potential to enhance the generation of nitric oxide in the juxtaglomerular apparatus during LS intake and of TxA2 during HS intake. This could contribute to kidney-specific regulation of vascular tone during changes in salt intake. The large increase in TxA2-S mRNA expression in the kidney cortex observed during HS intake may explain the finding that renal TxB2 excretion (and hence TxA2 generation in the body) increases two- to threefold during HS intake compared with LS intake (Fig. 1).

These results suggest that during LS intake there is normally a powerful stimulus for expression of TP-Rs in kidney cortex and brain stem. However, an associated increase in ANG II, acting on AT1-Rs, feeds back to reverse the effect of salt in the kidney and prevent the effect in the brain stem. This is analogous to studies of cyclooxygenase-2 (COX-2) in the kidney cortex. COX-2 expression is enhanced during LS intake; this effect is exaggerated by blockade of ANG II generation with an angiotensin-converting enzyme inhibitor (15). This has led to the hypothesis that ANG II feeds back to blunt salt-induced changes in COX-2 expression. The major difference in the renal regulation of TP-Rs and COX-2 appears to be in the relative importance of ANG II, which is predominant for TP-Rs, resulting in an actual reversal of the direct effects of salt on TP-R expression in the kidney.

A limitation of our study is the use of mRNA to assess receptor or enzyme function. However, there is a correlation among several findings with mRNA expression in the present series and functional data. Thus the 10-fold increase in TxA2-S mRNA expression in the kidney with HS intake (Fig. 4) is mirrored by a two- to threefold increase in TxB2 excretion (Fig. 1). The increase in TP-R mRNA expression in the kidney with HS intake (Fig. 2) is mirrored by the increased responsiveness of the afferent arteriole to U-46619 microperfused into the renal interstitium during HS intake (56) and the greater increase in blood pressure (55) and sympathetic nervous system activity (13) in response to prolonged infusion of U-46619 during HS intake. The finding that the expression of TP-R mRNA in the brain stem is downregulated by ANG II (Fig. 2) may be relevant to the interaction between ANG II and TP-Rs in the brain in the control of drinking (19).

Perspectives. There are several implications of our study. First, the upregulation of TP-Rs and TxA2-S in the kidney cortex during HS intake may contribute to the prohypertensive role of vasoconstrictor PGs in salt-dependent forms of hypertension, such as ANG II-salt hypertension (32), DOCA-salt (20, 38), or the Dahl salt-sensitive rat (50, 54, 63). Our laboratory had shown previously that hypertonic NaCl infusion selectively increases the release of TxB2 into urine and renal lymph (61). An accompanying increase in afferent and efferent arteriolar resistance is blocked by inhibition of COX or TxA2-S (5). The present finding that HS intake enhances TxB2 excretion and enhances TP-Rs and TxA2-S in the kidney cortex suggests that salt loading could increase TxA2 generation and response to TP-R activation. Third, HS intake potentiates the increase in blood pressure that occurs during a prolonged infusion of a TP-R mimetic (55) and the increase in afferent arteriolar vasoconstriction during local microperfusion of a TP-R mimetic into the kidney (56). This correlates with an increase in the mRNA for TP-Rs in the kidney during salt loading. Therefore, these new findings that salt intake and/or ANG II regulates TP-R and TxA2-S mRNA expression in the kidney and brain likely have functional significance.


    ACKNOWLEDGEMENTS

We are grateful to Dr. Bo Peng for technical assistance and Sharon Clements for the preparation of this manuscript.


    FOOTNOTES

This work was supported by National Institutes of Health Grants DK-49870, DK-36079, and PO1-HL-68686-01 and funds from the George E. Schreiner Chair of Nephrology.

Address for reprint requests and other correspondence: C. S. Wilcox, Div. of Nephrology and Hypertension, Georgetown Univ. Medical Ctr., 3800 Reservoir Rd., NW PHC F6003, Washington, DC 20007 (E-mail: wilcoxch{at}georgetown.edu).

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.

10.1152/ajprenal.00256.2002

Received 16 July 2002; accepted in final form 5 November 2002.


    REFERENCES
TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES

1.   Abe, T, Takeuchi K, Takahashi N, Tsutsumi E, Taniyama Y, and Abe K. Rat kidney thromboxane receptor: molecular cloning, signal transduction, and intrarenal expression localization. J Clin Invest 96: 657-664, 1995[ISI][Medline].

2.   Bonvalet, JP, Pradelles P, and Farman N. Segmental synthesis and actions of prostaglandins along the nephron. Am J Physiol Renal Fluid Electrolyte Physiol 253: F377-F387, 1987[Abstract/Free Full Text].

3.   Borg, C, Lim CT, Yeomans DC, Dieter JP, Komiotis D, Anderson EG, and Le Breton GC. Purification of rat brain, rabbit aorta, and human platelet thromboxane A2/prostaglandin H2 receptors by immunoaffinity chromatography employing anti-peptide and anti-receptor antibodies. J Biol Chem 269: 6109-6116, 1994[Abstract/Free Full Text].

4.   Bresnahan, BA, Le Breton GC, and Lianos EA. Localization of authentic thromboxane A2/prostaglandin H2 receptor in the rat kidney. Kidney Int 49: 1207-1213, 1996[ISI][Medline].

5.   Bullivant, EMA, Wilcox CS, and Welch WJ. Intrarenal vasoconstriction during hyperchloremia: role of thromboxane. Am J Physiol Renal Fluid Electrolyte Physiol 256: F152-F157, 1989[Abstract/Free Full Text].

6.   Chemtob, S, Beharry K, Rex J, Varma DR, and Aranda JV. Changes in cerebrovascular prostaglandins and thromboxane as a function of systemic blood pressure: cerebral blood flow autoregulation of the newborn. Circ Res 67: 674-682, 1990[Abstract].

7.   Chlopicki, S, Koda M, Chabielska E, Buczko W, and Gryglewski RJ. Antiplatelet action of losartan involves TXA2 receptor antagonism but not TXA2 synthase inhibition. J Physiol Pharmacol 51: 715-722, 2000[ISI][Medline].

8.   Demediuk, P, and Faden AI. Traumatic spinal cord injury in rats causes increases in tissue thromboxane but not peptidoleukotrienes. J Neurosci Res 20: 115-121, 1988[ISI][Medline].

9.   Deng, X, Welch WJ, and Wilcox CS. Role of nitric oxide in short-term and prolonged effects of angiotensin II on renal hemodynamics. Hypertension 27: 1173-1179, 1996[Abstract/Free Full Text].

10.   Folger, WH, Halushka PV, Wilcox CS, and Guzman NJ. Characterization of rat glomerular thromboxane A2 receptors: comparison to rat platelets. Eur J Pharmacol 227: 71-78, 1992[Medline].

11.   Folger, WH, Lawson D, Wilcox CS, and Mehta JL. Response of rat thoracic aortic rings to thromboxane mimetic U-46,619: roles of endothelium-derived relaxing factor and thromboxane A2 release. J Pharmacol Exp Ther 258: 669-675, 1991[Abstract].

12.   Gao, H, Peng B, Welch WJ, and Wilcox CS. Central thromboxane receptors: mRNA expression and mediation of pressor responses. Am J Physiol Regul Integr Comp Physiol 272: R1493-R1500, 1997[Abstract/Free Full Text].

13.   Gao, H, Welch WJ, Dibona GF, and Wilcox CS. Sympathetic nervous system and hypertension during prolonged TXA2/PGH2 receptor activation in rats. Am J Physiol Heart Circ Physiol 273: H734-H739, 1997[Abstract/Free Full Text].

14.   Halushka, PV, Allan CJ, and Davis-Bruno KL. Thromboxane A2 receptors. J Lipid Mediat Cell Signal 12: 361-378, 1995[ISI][Medline].

15.   Harris, RC, and Breyer MD. Physiological regulation of cyclooxygenase-2 in the kidney. Am J Physiol Renal Physiol 281: F1-F11, 2001[Abstract/Free Full Text].

16.   Hayashi, K, Loutzenhiser R, and Epstein M. Direct evidence that thromboxane mimetic U-44,069 preferentially constricts the afferent arteriole. J Am Soc Nephrol 8: 25-31, 1997[Abstract].

17.   Imig, JD, Kitiyakara C, and Wilcox CS. Arachidonate metabolites. In: The Kidney: Physiology and Pathophysiology, edited by Seldin DW, and Giebisch G.. New York: Raven, 2000, p. 875-889.

18.   Kitanaka, J, Hashimoto H, Sugimoto Y, Sawada M, Negishi M, Suzumura A, Marunouchi T, Ichikawa A, and Baba A. cDNA cloning of thromboxane A2 receptor from rat astrocytes. Biochim Biophys Acta 1265: 220-223, 1995[ISI][Medline].

19.   Kitiyakara, C, Welch WJ, Verbalis JG, and Wilcox CS. Role of thromboxane receptors in the dipsogenic response to central angiotensin II. Am J Physiol 10: R865-R869, 2002.

20.   Kosugi, T, Ikeda T, Gomi T, Ushijima T, and Okada J. Glomerular thromboxane contributes to pressor response in deoxycorticosterone acetate-salt hypertension. Prostaglandins Leukot Essent Fatty Acids 58: 129-133, 1998[ISI][Medline].

21.   Li, P, Ferrario CM, and Brosnihan KB. Losartan inhibits thromboxane A2-induced platelet aggregation and vascular constriction in spontaneously hypertensive rats. J Cardiovasc Pharmacol 32: 198-205, 1998[ISI][Medline].

22.   Lin, L, Balazy M, Pagano PJ, and Nasjletti A. Expression of prostaglandin H2-mediated mechanism of vascular contraction in hypertensive rats: relation to lipoxygenase and prostacyclin synthase activities. Circ Res 74: 197-205, 1994[Abstract].

23.   Lin, L, Mistry M, Stier CT, and Nasjletti A. Role of prostanoids in renin-dependent and renin-independent hypertension. Hypertension 17: 517-525, 1991[Abstract].

24.   Lin, L, and Nasjletti A. Role of endothelium-derived prostaglandin in angiotensin-induced vasconstriction. Hypertension 18: 158-164, 1991[Abstract].

25.   Loutzenhiser, R, Epstein M, Horton C, and Sonke P. Reversal of renal and smooth muscle actions of the thromboxane mimetic U-44069 by diltiazem. Am J Physiol Renal Fluid Electrolyte Physiol 250: F619-F626, 1986[Abstract/Free Full Text].

26.   Luft, FC, Wilcox CS, Unger T, Kuhn R, Demmert G, Rohmeiss P, Ganten D, and Sterzel RB. Angiotensin-induced hypertension in the rat: sympathetic nerve activity and prostaglandins. Hypertension 14: 396-403, 1989[Abstract].

27.   Mannon, RB, Coffman TM, and Mannon PJ. Distribution of binding sites for thromboxane A2 in the mouse kidney. Am J Physiol Renal Fluid Electrolyte Physiol 271: F1131-F1138, 1996[Abstract/Free Full Text].

28.   Mene, P, and Dunn MJ. Contractile effects of TxA2 and endoperoxide analogues on cultured rat glomerular mesangial cells. Am J Physiol Renal Fluid Electrolyte Physiol 251: F1029-F1035, 1986[Abstract/Free Full Text].

29.   Mene, P, Simonson MS, and Dunn MJ. Physiology of the mesangial cell. Physiol Rev 69: 1347-1424, 1989[Free Full Text].

30.   Miggin, SM, and Kinsella T. Expression and tissue distribution of the mRNAs encoding the human thromboxane A2 receptor (TP) alpha  and beta  isoforms. Biochim Biophys Acta 1425: 543-559, 1998[ISI][Medline].

31.   Mistry, M, Muirhead EE, Yamaguchi Y, and Nasjletti A. Renal function in rats with angiotensin II-salt-induced hypertension: effect of thromboxane synthesis inhibition and receptor blockade. J Hypertens 8: 75-83, 1990[ISI][Medline].

32.   Mistry, M, and Nasjletti A. Role of pressor prostanoids in rats with angiotensin II-salt-induced hypertension. Hypertension 11: 758-762, 1988[Abstract].

33.   Mistry, M, and Nasjletti A. Contrasting effect of thromboxane synthase inhibitors and a thromboxane receptor antagonist on the development of angiotensin II-salt-induced hypertension in rats. J Pharmacol Exp Ther 253: 90-94, 1990[Abstract].

34.   Nakahata, N, Ishimoto H, Kurita M, Ohmori K, Takahashi A, and Nakanishi H. The presence of thromboxane A2 receptors in cultured astrocytes from rabbit brain. Brain Res 583: 100-104, 1992[ISI][Medline].

35.   Nakahata, N, Matsuoka I, Ono T, and Nakanishi H. Thromboxane A2 activates phospholipase C in astrocytoma cells via pertussis toxin-insensitive G-protein. Eur J Pharmacol 162: 407-417, 1989[ISI][Medline].

36.   Nüsing, R, Goerig M, Habenicht AJ, and Ullrich V. Selective eicosanoid formation during HL-60 macrophage differentiation. Regulation of thromboxane synthase. Eur J Biochem 212: 317-376, 1993.

37.   Nüsing, R, and Ullrich V. Immunoquantitation of thromboxane synthase in human tissues. Eicosanoids 3: 175-180, 1990[ISI][Medline].

38.   Osanai, T, Kikuchi T, Yokono Y, Matsumura H, Minami O, Akiba R, Eidoh H, Konta A, Kanazawa T, Onodera K, Metoki H, and Oike Y. Role of renomedullary thromboxane A2 in development of DOCA-salt hypertension. Clin Exp Hypertens 13: 159-188, 1991.

39.   Pratico, D, O'Mahony D, Lawson J, Kinsella T, and FitzGerald GA. Cellular activation by thromboxane A2 and 8-epi-PGF2alpha . In: Eicosanoids and Other Bioactive Lipids in Cancer, Inflammation and Radiation Injury 2: Part A, , edited by Honn KV, Nigam S, and Marnett LJ.. New York and London: Plenum, 1997, p. 229-233.

40.   Ramos, EL, Barri YM, Croker BP, Clapp WL, Peterson JC, and Wilcox CS. Thromboxane synthase expression in renal transplant patients with rejection. Transplantation 59: 490-494, 1995[ISI][Medline].

41.   Reckelhoff, JF, Zhang H, Srivastava K, Roberts LJII, Morrow JD, and Romero JC. Subpressor doses of angiotensin II increase plasma F2-isoprostanes in rats. Hypertension 35: 476-479, 2000[Abstract/Free Full Text].

42.   Romero, JC, and Reckelhoff JF. Role of angiotensin and oxidative stress in essential hypertension. Hypertension 34: 943-949, 1999[Abstract/Free Full Text].

43.   Schnackenberg, CG, Welch WJ, and Wilcox CS. TP receptor-mediated vasoconstriction in microperfused afferent arterioles: role of O<UP><SUB>2</SUB><SUP>−</SUP></UP> and NO. Am J Physiol Renal Physiol 279: F302-F308, 2000[Abstract/Free Full Text].

44.   Seregi, A, Keller M, and Hertting G. Are cerebral prostanoids of astroglial origin? Studies on the prostanoid forming system in developing rat brain and primary cultures of rat astrocytes. Brain Res 404: 113-120, 1987[ISI][Medline].

45.   Seregi, A, Keller M, Jackisch R, and Hertting G. Comparison of the prostanoid synthesizing capacity in homogenates from primary neuronal and astroglial cell cultures. Biochem Pharmacol 33: 3315-3318, 1984[ISI][Medline].

46.   Shohami, E, Rosenthal J, and Lavy S. The effect of incomplete cerebral ischemia on prostaglandin levels in rat brain. Stroke 13: 494-499, 1982[Abstract].

47.   Sirko, S, Bishal I, and Coceani F. Prostaglandin formation in the hypothalamus in vivo: effect of pyrogens. Am J Physiol Regul Integr Comp Physiol 256: R616-R624, 1989[Abstract/Free Full Text].

48.   Takahashi, N, Takeuchi K, Abe T, Sugawara A, and Abe K. Immunolocalization of rat thromboxane receptor in the kidney. Endocrinology 137: 5170-5173, 1996[Abstract].

49.   Takeuchi, K, Tsutsumi E, Abe T, Takahashi N, Kato T, Taniyama Y, Ikeda Y, and Abe K. Assignment of rat thromboxane synthase gene (Tbxas) to chromosome 4q21-q22 by fluorescence in situ hybridization. Cytogenet Cell Genet 76: 47-48, 1997[ISI][Medline].

50.  Tobian L, Uehara Y, and Iwai J. Prostaglandin alterations in barely hypertensive Dahl S rats. Prostaglandins 378-383, 1919.

51.   Tojo, A, Kimoto M, and Wilcox CS. Renal expression of constitutive NOS and DDAH: separate effects of salt intake and angiotensin. Kidney Int 58: 2075-2083, 2000[ISI][Medline].

52.   Tojo, A, Madsen K, and Wilcox CS. Expression of immunoreactive nitric oxide synthase isoforms in rat kidney: effects of dietary salt and losartan. Jpn Heart J 36: 389-398, 1995[ISI][Medline].

53.   Tsutsumi, E, Takeuchi K, Abe T, Takahashi N, Kato T, Taniyama Y, Ikeda Y, Ito S, and Abe K. Rat kidney thromboxane synthase: cDNA cloning and gene expression regulation in hydronephrotic kidney. Prostaglandins 53: 423-431, 1997[Medline].

54.   Uehara, Y, Tobian L, Iwai J, Ishii M, and Sugimoto T. Alterations of vascular prostacyclin and thromboxane A2 in Dahl genetical strain susceptible to salt-induced hypertension. Prostaglandins 33: 727-738, 1987[Medline].

55.   Welch, WJ, Ahlstrom NG, and Wilcox CS. Mechanism of hypertension during prolonged infusion of thromboxane mimetic. Eur J Int Med 2: 277-280, 1992.

56.   Welch, WJ, Peng B, Takeuchi K, Abe K, and Wilcox CS. Salt loading enhances rat renal TxA2/PGH2 receptor expression and TGF responses to U-46,619. Am J Physiol Renal Physiol 273: F976-F983, 1997[Abstract/Free Full Text].

57.   Welch, WJ, and Wilcox CS. Modulating role for thromboxane in the tubuloglomerular feedback response in the rat. J Clin Invest 81: 1843-1849, 1988[ISI][Medline].

58.   Welch, WJ, and Wilcox CS. Potentiation of tubuloglomerular feedback in the rat by thromboxane mimetic. Role of macula densa. J Clin Invest 89: 1857-1865, 1992[ISI][Medline].

59.   Wilcox, CS, Cordozo J, and Welch WJ. AT1 and TxA2/PGH2 receptors maintain hypertension throughout 2K,1C Goldblatt hypertension in the rat. Am J Physiol Regul Integr Comp Physiol 271: R891-R896, 1996[Abstract/Free Full Text].

60.   Wilcox, CS, and Lin L. Vasoconstrictor prostaglandins in angiotensin-dependent and renovascular hypertension. J Nephrol 6: 124-133, 1993.

61.   Wilcox, CS, Roddis S, Peart WS, Gordon D, and Lewis GP. Intrarenal prostaglandin release: effects of arachidonic acid and hyperchloremia. Kidney Int 28: 43-50, 1985[ISI][Medline].

62.   Wilcox, CS, Welch WJ, and Snellen H. Thromboxane mediates renal hemodynamic response to infused angiotensin II. Kidney Int 40: 1090-1097, 1991[ISI][Medline].

63.   Yamashita, W, Ito Y, Weiss MA, Ooi BS, and Pollak VE. A thromboxane synthetase antagonist ameliorates progressive renal disease of Dahl-S rats. Kidney Int 33: 77-83, 1988[ISI][Medline].

64.   Yokoyama, C, Miyata A, Ihara H, Ullrich V, and Tanabe T. Molecular cloning of human platelet thromboxane A synthase. Biochem Biophys Res Commun 178: 1479-1484, 1991[ISI][Medline].


Am J Physiol Renal Fluid Electrolyte Physiol 284(3):F525-F531
0363-6127/03 $5.00 Copyright © 2003 the American Physiological Society