[Effect of endothelium-derived nitric oxide and prostaglandins on the endothelium-dependent vascular refractoriness to angiotensin II in pregnant rabbits].

Recently we demonstrated that the vascular response to angiotensin II (A-II) was attenuated in an endothelium-dependent manner by using the isolated ring specimen iliac arteries of pregnant rabbits. In this paper we investigated the possibility that three vasoactive substances, thromboxane A2(TXA2), prostacyclin (PGI2), and endothelium-derived nitric oxide (EDNO), might be involved in this refractoriness to A-II during pregnancy, by measuring the changes in the vascular response to A-II (pA2, intrinsic activity) of the isolated arterial rings of rabbits before and after the addition of an inhibitor specific for each of these three substances. Sodium ozagrel, TXA2 synthetase inhibitor, decreased the vascular response to A-II more in the blood vessels of pregnant rabbits, regardless of whether the endothelium was intact or denuded, than in the blood vessels of non pregnant rabbits. Tranylcypromine, a PGI2 synthetase inhibitor, significantly increased contractility in the blood vessels with intact endothelium of pregnant rabbits (i.a. = 1.39 +/- 0.099, n = 11, mean +/- SEM), compared to that in the blood vessels with intact endothelium of non pregnant rabbits (i.a. = 1.08 +/- 0.090, n = 7). Methylene blue, a guanylate cyclase inhibitor which blocks the effect of EDNO, amplified the vascular response in blood vessels with intact endothelium of both groups, and more intensely in the blood vessels of pregnant rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)