NO elicits prolonged relaxation of bovine pulmonary arteries via endogenous peroxynitrite generation.
We previously reported that acute exposure of endothelium-removed bovine pulmonary arteries (BPA) to high levels (0.1 mM) of peroxynitrite (ONOO-) caused a prolonged guanosine 3',5'-cyclic monophosphate-related relaxation that appeared to be mediated through a thiol-dependent generation of nitric oxide (NO). In this study, we examined the importance of endogenous ONOO- formation in the regulation of BPA force generation by elevated physiological levels of NO. Exposure of BPA precontracted with 30 mM KCl to approximately 50 nM NO for 2 min caused a subsequent prolonged relaxation of KCl-induced force and an increased release of NO (measured in head space gas after a 5-min deoxygenation with 95% N2-5% CO2). This subsequent release of NO was reduced after depletion of tissue glutathione with diethyl maleate (DEM). Also, the NO-elicited prolonged relaxation of BPA was reversed by post-NO treatment with 10 microM methylene blue (MB; which inhibits guanylate cyclase stimulation by NO) or 1 microM oxyhemoglobin (which traps NO). Furthermore, inhibiting the biosynthesis of endogenous superoxide anion (O2-.) with 1 microM diphenyliodonium (DPI) or scavenging O2-. with 10 mM Tiron also promoted reversal of the NO-elicited prolonged relaxation seen in BPA after NO gas exposure. During exposure of BPA smooth muscle to approximately 50 nM NO gas, there appears to be a marked increase in ONOO- formation as detected by a DPI- and Tiron-inhibitable prominent increase in luminol-dependent chemiluminescence and a decrease in O2-. levels as detected by a reduction in lucigenin-dependent chemiluminescence during exposure to NO. Thus, during exposure to elevated physiological levels of NO, BPA appear to produce ONOO-, a species that seems to participate in prolonging the initial relaxation to NO through a thiol-dependent trapping and/or regeneration of NO.
Davidson
C A
CA
Department of Physiology, New York Medical College, Valhalla 10595, USA.
Kaminski
P M
PM
Wolin
M S
MS
D000818:Animals; D002417:Cattle; D008163:Luminescent Measurements; D009566:Nitrates / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D011651:Pulmonary Artery / Q000502:physiology*; D013438:Sulfhydryl Compounds / Q000502:physiology; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors; D014664:Vasodilation / Q000502:physiology*
D009566:Nitrates; D013438:Sulfhydryl Compounds; D013481:Superoxides; C039642:peroxynitric acid; D009569:Nitric Oxide; D011189:Potassium Chloride