title: Hypoxia enhances a cGMP-independent nitric oxide relaxing mechanism in pulmonary arteries.
abstract: Nitric oxide (NO) donors generally relax vascular preparations through cGMP-mediated mechanisms. Relaxation of endothelium-denuded bovine pulmonary arteries (BPA) and coronary arteries to the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) is almost eliminated by inhibition of soluble guanylate cyclase activation with 10 microM 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), whereas only a modest inhibition of relaxation is observed under hypoxia (PO2 = 8-10 Torr). This effect of hypoxia is independent of the contractile agent used and is also observed with NO gas. ODQ eliminated SNAP-induced increases in cGMP under hypoxia in BPA. cGMP-independent relaxation of BPA to SNAP was not attenuated by inhibition of K+ channels (10 mM tetraethylammonium), myosin light chain phosphatase (0.5 microM microcystin-LR), or adenylate cyclase (4 microM 2',5'-dideoxyadenosine). SNAP relaxed BPA contracted with serotonin under Ca2+-free conditions in the presence of hypoxia and ODQ, and contraction to Ca2+ readdition was also attenuated. The sarcoplasmic reticulum Ca2+-reuptake inhibitor cyclopiazonic acid (0.2 mM) attenuated SNAP-mediated relaxation of BPA in the presence of ODQ. Thus hypoxic conditions appear to promote a cGMP-independent relaxation of BPA to NO by enhancing sarcoplasmic reticulum Ca2+ reuptake.
authors.affiliation: Department of Physiology, New York Medical College, Valhalla, NY 10595, USA. mike_wolin@nymc.edu
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Mingone
authors.forename: Sachin A
authors.initials: SA
authors.lastname: Gupte
authors.forename: Takafumi
authors.initials: T
authors.lastname: Iesaki
authors.forename: Michael S
authors.initials: MS
authors.lastname: Wolin
mesh_terms: D000818:Animals; D002417:Cattle; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011651:Pulmonary Artery / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology*; D019789:Tetraethylammonium / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D011810:Quinoxalines; D009569:Nitric Oxide; D019789:Tetraethylammonium; D026423:S-Nitroso-N-Acetylpenicillamine; D006162:Guanylate Cyclase; D006152:Cyclic GMP