INFLUENCE OF THE VASCULAR ENDOTHELIUM ON ANGIOTENSIN-II-INDUCED CONTRACTIONS IN RABBIT RENAL-ARTERY

The influence of vascular endothelium on angiotensin II-induced contra ction and the underlying mechanisms in the rabbit renal artery were in vestigated. In endothelium-intact preparations, angiotensin II (3-100 nM) caused a concentration-dependent increase in tension by maximally (E(max)) 0.74 +/- 0.05 g. Removal of the endothelium significantly enh anced the angiotensin II-induced 3.91 contractions (E(max): 3.91 +/- 0 .19 g). Indomethacin (10 mu M) did not influence the angiotensin II-in duced contractions. Methylene blue (10 mu M) and N-G-methyl-1-arginine (L-NMMA, 5 mu M) significantly enhanced angiotensin II-induced contra ctions by 418 +/- 29% and 200 +/- 14%, respectively, in endothelium in tact preparations, but not in those devoid of endothelium. L-arginine (1 mM), but not D-arginine, reversed the L-NMMA-induced enhancement of the angiotensin II-induced contraction. The present results suggest t hat angiotensin II-induced contractions in rabbit renal artery are lar gely subject to the influence of the endothelium. The endothelium-deri ved relaxant factor (EDRF), rather than cyclo-oxygenase products, appe ars to be involved in mediating the inhibitory effects of the endothel ium. Nitric oxide (NO) derived from endothelium may play a major role in inhibiting angiotensin II-induced contractions in this preparation.