title: Kinetic analyses of the effects of hyperoxia and hypoxia on vascular cyclooxygenase activity in vitro.
abstract: Kinetic analyses were performed to understand the mechanism of hyperoxic induced inhibition of prostacyclin synthesis by human umbilical arteries. Brief exposure of arterial segments to oxygen resulted in over 30% decrease in Vmax of cyclooxygenase in treated vessels. In contrast, cyclooxygenase from hypoxic arterial segments showed approximately a 49% increase in Vmax. There were no significant differences in apparent Km values. These studies suggest that the decreased production of prostacyclin by hyperoxic tissue is due to cyclooxygenase inactivation.
mesh_terms: D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D006801:Humans; D006931:Hyperbaric Oxygenation; D000860:Hypoxia / Q000201:enzymology*; D007231:Infant, Newborn; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D013997:Time Factors; D014469:Umbilical Arteries / Q000378:metabolism*
chemical_list: D001095:Arachidonic Acids; D016718:Arachidonic Acid; D011451:Prostaglandin-Endoperoxide Synthases