Serotonin transport and fluidity in plasma membrane vesicles: effect of hyperoxia.
Plasma membrane vesicles were prepared from porcine pulmonary artery endothelial cells by a dextran-polyethylene glycol two-phase system. Specific carrier-mediated transport of 5-hydroxytryptamine (5-HT) into the vesicles was examined. Transport required a Na+ gradient (out greater than in) across the membrane, and accumulated 5-HT rapidly effluxed out of the vesicles when the ionophore gramicidin was added. Transport was inhibited by the antidepressant imipramine. 5-HT transport into plasma membrane vesicles appeared saturable and exhibited Michaelis-Menten kinetics (Km 7.4 microM, maximal velocity 217 pmol.min-1.mg membrane protein-1). A 24-h exposure to 95% O2 at 1 atmosphere absolute resulted in a 21% decrease (P less than 0.05) in specific 5-HT transport by plasma membrane vesicles. Hyperoxia also caused a significant (P less than 0.01) decrease in plasma membrane fluidity, as measured with the fluorescence probe 1,6-diphenyl-1,3,5-hexatriene. These results indicate that pulmonary artery endothelial cell plasma membrane vesicles provide a good model for studying 5-HT transport activity in vitro. Hyperoxia affects plasma membrane fluidity and 5-HT transport in pulmonary artery endothelial cells, suggesting a possible cause-and-effect relationship between the two.
Sheridan
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Research Service, Veterans Administration Medical Center, Gainesville, Florida.
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D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000648:ultrastructure; D007099:Imipramine / Q000494:pharmacology; D007700:Kinetics; D008560:Membrane Fluidity; D008954:Models, Biological; D010100:Oxygen / Q000502:physiology*; D011651:Pulmonary Artery; D012701:Serotonin / Q000378:metabolism*; D013552:Swine
D012701:Serotonin; D007099:Imipramine; D010100:Oxygen