title: Reversal of acetylcholine-induced coronary resistance vessel dilation by hemoglobin.
abstract: In large arteries, acetylcholine-induced dilation is mediated by endothelium-derived relaxing factor (EDRF) and can be blocked by hemoglobin (Hb). However, the role of EDRF in the microcirculation is uncertain. Therefore, the effect of Hb on acetylcholine-induced dilation of resistance vessels was studied in isolated, constant-flow perfused rabbit hearts. Hb reversibly blocked the acetylcholine-induced lowering of perfusion pressure (control -27 +/- 3%; during Hb 0 +/- 4%) without inhibiting responses to other dilators, strongly suggesting that acetylcholine action in the microcirculation is mediated by EDRF.
mesh_terms: D000109:Acetylcholine / Q000037:antagonists & inhibitors*; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects; D005260:Female; D006454:Hemoglobins / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D010477:Perfusion; D011817:Rabbits; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D006454:Hemoglobins; D000109:Acetylcholine