Chronic Blockade of Nitric Oxide Synthase and Endothelin Receptors During Pregnancy in the Rat: Effect on Reactivity of the Uterine Artery In Vitro

Abstract

Objective: To investigate the effects of chronic blockade of nitric oxide (NO) production and endothelin (ET-1) receptor antagonism on edothelial and vascular smooth muscle function of the uterine artery in vitro obtained from nonpregnant and pregnant rats.

Methods: Pregnant or nonpregnant Wistar rats wee either treated orally for up to 18 days with the NO synthase inhibitor N^ω-nitro-L-arginine methyl ester (L-NAME), the ET_A-/ET_B-receptor antagonist bosentan, or both, or they received no treatment (controls). Absolute contractile force as well as endothelium-dependent and -independent vascular reactivity of uterine arteries were determined in vitro. Isometric tension was recorded. ANOVA and the Mann-Whitney U test were used for statistical analysis.

Results: Pregnancy increased obsolute tension (mN/mm) elicited in uterine arteries by ET-1 (P < .01), serotonin (P < .05), norepinephrine (P < .02), and KCl (P < .0001). Chronic treatment with L-NAME or L-NAME plus bosentan, but not with bosentan alone, reduced contractions to KCl in pregnant and nonpregnant rats (P < .005-.0001), while pregnancy-induced enhancement in tension development remained unchanged in all groups (P < .005). After exposure of uterine arteries to L-NAME in vitro, vascular sensitivity to ET-1 was augmented in uterine arteries of pregnant but not of nonpregnant animals (P < .05).

L-NAME-pretreatmetn did not influence the pregnancy-induced increase of vascular sensitivity to acetylcholine but reduced maximal relaxation in nonpregnant animals (P < .05). In addition, pregnancy diminished sensitivity of uterine arteries to sodium nitroprusside (P < .002), which was abolished by chronically administered L-NAME. Bosentan had no influence on vasodilation in vitro.

Conclusion: Neither endothelin-1 nor nitric oxide seem to contribute to the augmented tension to depolarization and receptor-operated stimulation of vascular smooth muscle cells in rat uterine arteries during pregnancy. In addition, pregnancy is associated with increased NO production in uterine arteries, as evidenced by augmented endothelium-dependent relaxations, increased NO release by endothelin-1, and decreased sensitivity to sodium nitroprusside.

Keywords

Acetylcholine bosentan endothelium endothelin-1 Nω-nitro-L-arginine methyl ester (L-NAME)uterine arteries rats

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References

1. Blizard DA , Folk TG . Resource sharing in rat gestation: role of maternal cardiovascular hemodynamics. Am J Physiol 1990;258:R1299-R1307.

2. Robertson WB , Brosens I , Dixon G . Uteroplacental vascular pathology. Eur J Obstet Gynecol Reprod Biol 1975;5:47-65.

3. Ni Y , May V , Braas K , Osol G . Pregnancy augments uteroplacental vascular endothelial growth factor gene expression and vasodilator effects. Am J Physiol 1997;273-H938-H944.

4. Weiner CP , Lizasoain I , Baylis SA , Knowles RG , Charles IG , Moncada S . Induction of calcium-dependent nitric oxide synthases by sex hormones. Proc Natl Acad Sci USA 1994;91:5212-5216.

5. Magness RR , Shaw CE , Phernetton TM , Zheng J , Bird IM . Endothelial vasodilator production by uterine and systemic arteries. II. Pregnancy effects on NO synthase expression. Am J Physiol 1997;272:H1730-H1740.

6. Rosenfeld CR , Cox BE , Roy T , Magness RR . Nitric oxide contributes to estrogen-induced vasodilation of the ovine uterine circulation. J Clin Invest 1996;98:2158-2166.

7. Ni Y , Meyer M , Osol G . Gestation increases nitric oxidemediated vasodilation in rat uterine arteries. Am J Obstet Gynecol 1997;176:856-864.

8. Sladek SM , Magness RR , Conrad KP . Nitric Oxide and pregnancy. Am J Physiol 1997;272:R441-R463.

9. Weiner CP , Thompson LP , Liu K , Herrig JE . Endothelium-derived relaxing factor and indomethacin-sensitive contracting factor alter arterial contractile responses to thromboxane during pregnancy. Am J Obstet Gynecol 1992;166:1171-1181.

10.

10. Conrad KP , Colpoys MC . Evidence against the hypothesis that prostaglandins are the vasodepressor agents of pregnancy. J Clin Invest 1986;7:236-245.

11.

11. Magness RR , Rosenfeld CR , Hassan A , Shaul PW . Endothelial vasodilator production by uterine and systemic arteries. I. Effects of ANG II on PGI2 and NO in pregnancy. Am J Physiol 1996;270:H1914-H1923.

12.

12. Weiner CP , Liu KZ , Thompson L , Herrig J , Chestnut D . Effect of pregnancy on endothelium and smooth muscle: their role in reduced adrenergic sensitivity. Am J Physiol 1991;261:1275-1283.

13.

13. Yanagisaa M , Kurihara H , Kimura S , et al. A novel potent vasoconstrictor peptide produced by vascular endothelial cells. Nature 1988;332:411-415.

14.

14. Arai H , Hori S , Aramori I , Ohkubo H , Nakanishi S . Cloning and expression of cDNA encoding an endothelin receptor. Nature 1990:348:370-373.

15.

15. Sakurai T , Yanagisawa M , Takura Y , Cloning of a cDNA encoding a non-isopeptide-selective subtype of the endothelin receptor. Nature 1990;348:732-735.

16.

16. Seo B , Oemar BS , Siebenmann R , von Segesser L , Lüscher TF . Both ETA- and ETB-receptors mediate contraction to endothelin-1 in human blood vessels. Circulation 1994;89:1202-1208.

17.

17. Warner TF , Mitchell JA , de Nucci G , Vane JR . Endothelin-1 and endothelin-3 release EDRF from isolated perfused arterial vessels of the rat and the rabbit. J Cardiovase Pharmacol 1989;13(Suppl 5):85-88.

18.

18. Metha JL , Lawson DL , Yang BC , Metha P , Nichols WW . Modulation of vascular tone by endothelin-1: role of preload, endothelial integrity and concentration of endothelin-1. Br J Pharmacol 1992;106:127-132.

19.

19. Haynes WG , Webb Dj . Contribution of endogenous generation of endothelin-1 to basal vascular tone. Lancet 1994;344:852-854.

20.

20. Lopez JA , Armstrong ML , Piegors DJ , Heistad DD . Vascular responses to endothelin-1 in atheorosclerotic primates. Atherosclerosis 1990;10:1113-1118.

21.

21. Kamoi K , Sudo N , Ishibashi M , Yamaji T . Plasma endothlin-1 levls in patints with pregnancy-induced hypertension. N Engl J Med 1990;323:1486-1487.

22.

22. Harvey-Wilkes KB , Nielsen HC , D'Alton ME . Elevated endothelin levels are associated with increased placental resistance. Am J Obstet Gynecol 1996;174:1599-1604.

23.

23. Clozed M , Breu V , Cassal JM , et al. Pathophysiological role of endothelin revealed by the first orally active endothelin receptor antagonist. Nature 1993;365:759-761.

24.

24. Raschack M , Unger L , Riechers H , Klinge D . Receptor selectivity of endothelin antagonists and preventin of vasoconstriction and endothelin-induced sudden death. J Cardiovasc Pharmacol 1995;26(Suppl 3):397-399.

25.

25. Haynes WG , Ferro CJ , O'Kane KPJ , Somerville D , Lomax CC , Webb DJ . Systemic endothelin receptor blockade decreases peripheral vascular resistance and blood pressure in humans. Circulation 1996;93:1860-1870.

26.

26. Wight E , Küng CF , Moreau P , Takase H , Lüscher TF . Chronic blockade of nitric oxide-synthase and endothelin receptors during pregnancy in the rat: effect on pregnancy outcome. J Soc Gynecol Invest 1998;5:132-139.

27.

27. Takase H , Moreau P , Küng CF , Nava E , Lüscher TF . Antihypertensive therapy prevents endothelial dysfunction in chronic nitric oxide deficiency. Effect of verapamil and trandolapril. Hypertensin 1996;27:25-31.

28.

28. Clozel M , Breu V , Gray GA , et al. Pharmacological characterization of bosentan, a new potent orally active nonpeptide endothelin receptor antagonist. J Pharmacol Exp Ther 1994;270:228-235.

29.

29. Mulvany MJ , Halpern W . Contractile properties of small arterial resistance vessels in spontaneously hypertensive and normotensive rats. Circ Res 1977;41:19-26.

30.

30. Wallenstein S , Zucker CL , Fleiss JL . Some statistical methods useful in circulation research. Circ Res 1980;47:1-9.

31.

31. Molnár M , Sütö T , Tóth T , Hertelendy F . Prolonged blockade of nitric oxide synthesis in gravid rats produces sustained hypertension, proteinura, thrombocytopenia, and intrauterine growth retardation. Am J Obstet Gynecol 1994;170:1458-1466.

32.

32. Diket AL , Pierce MR , Munshi UK , et al. Nitric oxide inhibition causes intrauterine growth retardation and hind-limb disruptions in rats. Am J Obstet Gynecol 1994;171:1243-1250.

33.

33. Helmbrecht GD , Farhat MY , Merrill S , et al. The role of nitric oxide in maintenance of uterine artery vascular tone during pregnancy. Am J Obstet Gynecol 1995;172:318-318.

34.

34. Yallampalli C . Garfield RE . Inhibition of nitric oxide synthesis in rats during pregnancy produces signs similar to those of preeclampsia. Am J Obstet Gynecol 1993;169:1316-1320.

35.

35. Cipolla M , Osol G . Hypertrophic and hyperplastic effects of pregnancy on the rat uterine wall. Am J Obstet Gynecol 1994;171:805-811.

36.

36. Osol G , Cipolla M . Interaction of myogenic and adrenergic mechanisms in isolated, pressurized uterine radial arteries from late-pregnant and nonpregnant rats. Am J Obstret Gynecol 1993;168:697-705.

37.

37. Dubin D , Pratt RE , Cooke JP , Dzau VJ . ENdothelin, a potent vasoconstrictor, is a vascular smooth muscle mitogen. J Vasc Med Biol 1989;1:13-17.

38.

38. Steele SC , Warren Ay , Johnson IR . Effect of the vascular endothelium on norepinephrine-induced contractions in uterine radial arteries from the nonpregnant and pregnant human uterus. Am J Obstet Gynecol 1993;168:1623-1628.

39.

39. Garg UC , Hassid A . Nitric oxide-generating vasodilators and 8-bromo-cyclic guanosine monophosphate inhibit mitogenesis and proliferation of cultured rat smooth muscle cells. J Clin Invest 1989;83:1774-1777.

40.

40. Dubey RK , Ganten D , Lüscher TF . Enhanced migration of smooth muscle cells from Ren-2 transgenic rats in response to angiotensin II: Inhibition by nitric oxide. Hypertension 1993;22:412-412.

41.

41. Moreau P , d'Uscio LV , Shaw S , Takase H , Barton M , Lüscher TF . Angiotensin II increases tissue endothelin and induces vascular hypertrophy: reversal by ET(A)-receptor antagonist. Circulation 96:1593-1597.

42.

42. Li J , Schiffrin EL . Resistance artery structure and neuroeffector mechanisms in hypertension induced by inhibition of nitric oxide synthase. Am J Hypertens 1994;7:996-1004.

43.

43. Richard V , Hogie M , Clozel M , Löffler B , Thuillez C . In vivo evidence of an endothelin-induced vasopressor tone after inhibition of nitric oxide synthesis in rats. Circulation 1995;91:771-775.

44.

44. Weiner CP , Knowles RG , Moncada S . Induction of nitric oxide synthases early in pregnancy. Am J Obstet Gynecol 1994;171:838-843.

45.

45. Izumi H , Makino Y , Shirakawa K , Garfield RE . Role of nitric oxide on vasorelaxation in human umbilical artery. Am J Obstet Gynecol 1995;172:1477-1484.

46.

46. Pohl U , Busse R . Endothelium-derive relaxant factor inhibits effects of nitrocompounds in isolated arteries. Am J Physiol 1987;252:H307-H313.