Platelet-activating factor effects on bovine pulmonary artery endothelial cells.
Endothelial cells (ECs) were isolated from bovine pulmonary artery and maintained in long-term culture. On reaching confluency, ECs formed a characteristic "cobblestone" monolayer. One hour after addition of 1 nM platelet-activating factor (PAF) to the growth medium, ECs underwent dramatic changes in shape from their normal polygonal morphology to more elongated spindle-shaped forms. More pronounced effects were evident in the presence of 0.1 nM phorbol-12-myristate-13-acetate (PMA), a potent activator of C kinase. It was found that at concentrations from 10(-11)-10(-7) M, PAF stimulates the phosphoinositide turnover in EC. The half-maximal activation in the release of inositol phosphates was at 10(-9) M. This finding suggested that an increase in intracellular Ca2+ concentration and activation of protein kinase C were involved in the mechanism of action of PAF on EC. The metabolic responses of EC were evaluated by measuring the activity of beta-adrenergic receptor-coupled adenylate cyclase (AC) in a crude membrane fraction and by assay of prostacyclin and thromboxane released by cultured EC. AC from control membranes was activated by isoproterenol in a dose-dependent manner (EC50 = 30 nM) from 0.8-5.5 pmol cAMP/min/mg protein. If the membranes were isolated after preincubation of ECs with 1 nM PAF or 0.1 nM PMA, the AC activity was decreased by 70 and 90%, respectively; in both cases, affinity for isoproterenol was lowered threefold (EC50 = 100 nM). Our data suggest that PAF interaction with EC leads to an apparent beta-adrenergic receptor desensitization that probably acts via a phosphorylation mechanism involving C kinase.(ABSTRACT TRUNCATED AT 250 WORDS)
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004727:Endothelium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011464:Epoprostenol / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013929:Thromboxane B2 / Q000378:metabolism
D010716:Phosphatidylinositols; D010972:Platelet Activating Factor; D013929:Thromboxane B2; D011464:Epoprostenol; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D013755:Tetradecanoylphorbol Acetate