Vasodilation induced by acetylcholine and by glyceryl trinitrate in rat aortic and mesenteric vasculature.
In endothelium-containing rings of rat aorta which had been precontracted with phenylephrine, addition of acetylcholine (ACh) (0.010-10 microM) resulted in concentration-dependent, graded relaxation through the release of endothelium-derived relaxing factor (EDRF). Hemoglobin (3 and 10 microM) and methylene blue (10 microM) both produced marked inhibition of this EDRF-mediated relaxation. In the perfused mesenteric arterial vasculature of the rat, ACh-induced vasodilation was also inhibited by hemoglobin and by methylene blue, although to a lesser extent than was ACh-induced relaxation of aortic rings by these two agents. These findings indicate that EDRF mediates in large part ACh-induced relaxation of resistance vessels in the mesenteric vascular bed as well as large arteries. The nitrovasodilator glyceryl trinitrate (GTN) caused endothelium-independent relaxation of aortic rings as well as vasodilation of mesenteric arterial vasculature. GTN-induced relaxation of aortic rings was antagonized by hemoglobin as well as methylene blue, but to a lesser extent than was ACh-induced relaxation. However, hemoglobin did not inhibit and methylene blue actually potentiated GTN-induced vasodilation in the perfused mesenteric vasculature. Possible explanations of these paradoxical results are discussed.
Khan
M T
MT
Department of Pharmacology, SUNY Health Sciences Center, Brooklyn 11203.
Jothianandan
D
D
Matsunaga
K
K
Furchgott
R F
RF
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology; D006454:Hemoglobins / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology*; D008751:Methylene Blue / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology; D005996:Nitroglycerin / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014664:Vasodilation / Q000187:drug effects*
D006454:Hemoglobins; D010656:Phenylephrine; D009569:Nitric Oxide; D005996:Nitroglycerin; D000109:Acetylcholine; D008751:Methylene Blue