Effect of the stable endoperoxide analog U-46619 on prostacyclin production and cyclic AMP levels in bovine endothelial cells

Abstract

The effects of the stable endoperoxide analog U46619 (U) on the regulation of prostacyclin (PGI 2) formation and cyclic adenosine monophosphate (cAMP) were investigated in cultured bovine aortic endothelial (BAE) cells. Incubation of U (0.3, 3.0 and 30 uM) with BAE cells for 5 min results in a dose-dependent increase in PGI 2. Cyclic AMP levels were not changed at 0.3 and 3.0 uM but were stimulated at 30 uM U. When cells were exposed to U for a second and third 5 min period, PGI 2 formation at 0.3 and 3.0 uM U remained stimulated while at 30 uM, PGI 2 was not increased. Five min incubation of BAE cells with the cyclooxygenase inhibitor indomethacin blocked the stimulation of PGI 2 at all concentrations of U and also prevented the increase of cAMP levels at 30 uM. In cells prelabeled with 3H-arachidonate, U stimulated release of labeled products at 0.3 and 3.0 uM but not at 30 uM U. In cells treated with bradykinin in the presence of U, PGI 2 production was stimulated at 0.3 and 3.0 uM but not 30 uM U. When cells were exposed to U and stimulated with PGI 2 (with and without phosphodiesterase inhibition), U caused significant increases in cAMP. We conclude that incubation of BAE cells with U results in an initial dose-dependent increase in PGI 2 formation. Cyclic AMP levels are increased at high concentrations of U. This increase in cAMP is mediated by the initial stimulated PGI 2 and results in decreased PGI 2 on further exposure to U. Data suggest that U stimulates phospholipase activity and, at high concentrations, inhibits phosphodiesterase.