Elevated cAMP levels via isoproterenol attenuated ATP-stimulated PGI2 release (from 34.6 to 18.1 ng/min) and EDRF release in cultured bovine aortic endothelial cells.
Elevated cAMP levels attenuate ATP-induced increases in intracellular calcium and the subsequent release of autacoids (PGI2 and EDRF) in endothelial cells.
The effects of elevated levels of adenosine 3',5'-cyclic monophosphate (cAMP), in cultured endothelial cells from bovine aorta, on the ATP-induced increases in the intracellular free calcium concentration ( Ca2+i) and the release of prostaglandin I2 (PGI2) and endothelium-derived relaxant factor (EDRF) were investigated. Endothelial cAMP production was assessed in terms of cAMP release in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine; this release was increased fivefold by isoproterenol (1 microM), 1.6-fold by isoproterenol (0.1 microM), and 1.5-fold by the stable PGI2 analogue iloprost (10 microM). Ca2+i, measured with the fluorescent probe indo-1, was increased by ATP (1 microM) from 150 +/- 20 (SE) to 410 +/- 50 nM. Neither isoproterenol nor iloprost changed Ca2+i in unstimulated cells, but they significantly reduced Ca2+i levels in the presence of ATP. Similar inhibitions of increases in Ca2+i as by iloprost and isoproterenol (0.1 microM) were evoked by dibutyryl-cAMP (100 microM). Release of PGI2 was enhanced from 3.9 +/- 0.5 to 34.6 +/- 6 ng.min-1.5 x 10(6) cells-1 by ATP (3 microM); in the presence of isoproterenol, the ATP-stimulated release was reversibly reduced to 18.1 +/- 4.9 ng/min. Release of EDRF was assayed in terms of its stimulatory action on purified soluble guanylate cyclase. EDRF release in the first minute after stimulation with ATP (10 microM) was significantly attenuated by isoproterenol from 32.3 +/- 4.8 to 23.0 +/- 4.6 nmol.min-1.mg-1 (activity of soluble guanylate cyclase).(ABSTRACT TRUNCATED AT 250 WORDS)
Lückhoff et al. (Sun,) conducted a other in Cultured endothelial cells from bovine aorta. cAMP elevation (isoproterenol, iloprost, dibutyryl-cAMP) vs. ATP stimulation alone was evaluated on ATP-induced increases in intracellular free calcium concentration and release of PGI2 and EDRF. Elevated cAMP levels via isoproterenol attenuated ATP-stimulated PGI2 release (from 34.6 to 18.1 ng/min) and EDRF release in cultured bovine aortic endothelial cells.