Endothelium‐dependent relaxation induced by angiotensin II and histamine in isolated arteries of dog

Abstract

1 In helical strips of dog renal and mesenteric arteries pre-contracted with prostaglandin F_2α (PGF_2α), endothelium-dependent relaxations were investigated. Removal of the endothelium was shown histologically by staining with silver nitrate and functionally by testing the inability of acetylcholine to induce arterial relaxations. 2 When the endothelium was removed, relaxation of renal arteries to angiotensin (Ang) II was markedly suppressed, whereas relaxations induced by PGI₂ or isoprenaline were attenuated only slightly. Removal of the endothelium attenuated the relaxant response of mesenteric arteries to histamine but did not significantly alter the response to PGI₂. 3 Treatment with indomethacin caused an additional attenuation of the relaxant response to histamine or a reversal of the Ang II-induced relaxation to a contraction in the arterial strips, from which the endothelium had been removed. 4 Relaxation of renal arteries induced by Ang II and of mesenteric arteries induced by histamine is postulated to result from PGI₂ released from the arterial wall. Therefore, it appears that the endothelium is a major site but not the only site responsible for drug-induced release of PGI₂.