Abstract
In the presence of ouabain, prostaglandin (PG) E2 stimulated a gradual secretion of catecholamines from cultured bovine adrenal chromaffin cells. PGE2 or ouabain alone evoked a marginal secretory response. The synergism of ouabain was also observed with muscarine. PGE2, like muscarine, induced a concentration-dependent formation of inositol phosphates: rapid rises in inositol trisphosphate and inositol bisphosphate followed by a slower accumulation of inositol monophosphate. This effect on phosphoinositide metabolism was accompanied by an increase in cytosolic free Ca2+. The potency of PGs (PGE2 greater than PGF2 alpha greater than PGD2) to stimulate catecholamine release was well correlated with that to affect phosphoinositide metabolism and that to increase the level of intracellular Ca2+. PGE2 did not stimulate cAMP generation significantly in bovine chromaffin cells. The effect of PGE2 on catecholamine release was mimicked by 12-O-tetradecanoylphorbol 13-acetate and A23187, but not by the cAMP analogue dibutyryl cAMP nor by forskolin. These results indicate that PGE2 may enhance catecholamine release from chromaffin cells by activating protein kinase C in concert with the increment of intracellular Ca2+.
Highlights
13-acetateand A23187, but not bythe cAMP analogue dibutyryl cAMP nor by forskolin. These results indicate that PGEzmayenhancecatecholaminerelease from chromaffin cells by activating protein kinase C in concertwith the increment of intracellular Ca2+
Effect of PGEz and Muscarine onCatecholamineRelease from Bovine Adrenal Chromaffin Cells-As reported previously [13],incubation of chromaffin cells with 10 p~ nicotine induced a rapid and transient secretion of catecholamines, 8% of the total being released during a 15-min period
PGE, and ouabain together enhanced catecholamine release drastically from 1.56 k 0.04 to 11.94 f 0.34%. This synergistic effect of ouabain was observed with 100 PM muscarine, which did not induce catecholamine release by itself from bovinechromaffin cells ((7,8) Fig. 1).The time course of catecholamine release was slow at the onset and progressive at least until 30 min, similar to that induced by ouabain alone [16]
Summary
Enhancement of Catecholamine Release May Be Mediated by Phosphoinositide Metabolismin Bovine Adrenal ChromaffinCells*. Minnmi-ku, Kyoto 601, Japan could be related to the regulation of catecholamine release using cultured bovine chromaffin cells. The with IPS and involved in secretion of catecholamines from potency of PGs (PGE2 > PGF2, > PGD2) to stimulate bovine adrenal chromaffincells. Cell Culture,Catecholamine Release,andcAMPAssay-Chromaffin stimulate cAMP generation significantly inbovine cells were prepared from bovine adrenal medulla as described previchromaffincells. The medium wasquickly aspirated and 5% (w/v) trichloroacetic acid solution was added to each well, of muscarinic receptors results in increased phosphoinositide Separation of [’HJIPs was carried out by Bio-Rad AG1-X8 chromametabolism [4] The products of this pathway, inositol tris- tography essentially as described by Berridge et al [14]. Formation of [3H] IPS was dose-dependent over the concentrations from 10 nM to 10 p ~ w,ith half-maximal stimulation occurring at about 0.5 pM
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