title: Relaxation induced by acetylcholine involves endothelium-derived hyperpolarizing factor in 2-kidney 1-clip hypertensive rat carotid arteries.
abstract: Acetylcholine induced relaxation in a concentration-dependent way in isolated phenylephrine-contracted carotid artery rings from normotensive two-kidney (2K) and hypertensive two-kidney one-clip (2K-1C) rats. In the presence of the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NOARG, 100 micromol/l), the relaxation stimulated with acetylcholine was blocked in 2K arteries. However, in 2K-1C arteries, the relaxation was only partially inhibited. Indomethacin (3 micromol/l) had no effect in both groups. In 2K arteries, the combination of L-NOARG and indomethacin had similar effects to L-NOARG alone. On the other hand, in 2K-1C arteries, indomethacin further inhibited the maximum effect induced by acetylcholine. Endothelium-dependent relaxation induced by acetylcholine was markedly reduced in 2K arteries contracted with 90 mmol/l KCl, and it was abolished in 2K-1C arteries. The remaining response to acetylcholine in 2K arteries was blocked by L-NOARG. Thus, in addition to NO, a relaxing factor sensitive to extracellular K+ changes in the membrane potential contributes to endothelium-dependent relaxation in 2K-1C rat carotid artery. On the other hand, in arteries from 2K rats, only NO is involved in the relaxation induced by acetylcholine. The combination of 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, 3 micromol/l), indomethacin (3 micromol/l) and L-NOARG (100 micromol/l) reduced the relaxation induced by acetylcholine in arteries from 2K-1C rats contracted with phenylephrine. On the other hand, in 2K arteries, the relaxation induced by acetylcholine was abolished. The combination of ODQ and K+ channel blockers charybdotoxin (100 nmol/l), apamin (500 nmol/l) and 4-aminopyridine (1 micromol/l) abolished the relaxation induced by acetylcholine in 2K and 2K-1C carotid arteries. These data indicate that the endothelium-derived relaxing factors that contribute to relaxation induced by acetylcholine are different in 2K and 2K-1C arteries. In 2K arteries, the only factor is NO, which involves the activation of K+ channels and the cGMP pathway. However, in 2K-1C arteries, the relaxation induced by acetylcholine is dependent on NO in addition to another factor, which is insensitive to indomethacin, but also activates the K+ channels and the cGMP pathway, presumably by membrane hyperpolarization through endothelium-derived hyperpolarizing factor.
authors.affiliation: Laboratório de Farmacologia, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Brazil.
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Sendão Oliveira
authors.forename: Lusiane M
authors.initials: LM
authors.lastname: Bendhack
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001685:Biological Factors / Q000502:physiology*; D002339:Carotid Arteries / Q000187:drug effects / Q000503:physiopathology*; D006152:Cyclic GMP / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000502:physiology; D006454:Hemoglobins / Q000494:pharmacology; D006978:Hypertension, Renovascular / Q000503:physiopathology*; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052248:Nitric Oxide Synthase Type I; D019335:Nitroarginine / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D001685:Biological Factors; D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D006454:Hemoglobins; D009419:Nerve Tissue Proteins; D010069:Oxadiazoles; D026902:Potassium Channel Blockers; D011810:Quinoxalines; D014665:Vasodilator Agents; C067410:endothelium-dependent hyperpolarization factor; D019335:Nitroarginine; D009569:Nitric Oxide; D011189:Potassium Chloride; D011464:Epoprostenol; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D006152:Cyclic GMP; D000109:Acetylcholine; D007213:Indomethacin