Ota S, Hata Y, Terano A, Yoshiura K, Hiraishi H, Kawabe T, Mutoh H, Shiina S, Sugimoto T
Second Department of Internal Medicine, University of Tokyo, Japan.
Dig Dis Sci. 1993 Aug;38(8):1426-34. doi: 10.1007/BF01308599.
Prostaglandin (PG) has been reported to be one of the important protective factors in the gastric mucosa. However the mechanism of the regulation of endogenous PG production has not been well studied. We investigated the possible roles of Ca2+, cAMP, and protein kinase C (PKC) in the regulation of PGE2 release from cultured rabbit gastric mucosal cells. PGE2 was measured by radioimmunoassay. A23187 (Ca2+ ionophore) at 2 x 10(-6) M significantly increased PGE2 release. Deprivation of Ca2+ from the medium blocked the A23187-induced increase of PGE2. TMB-8 (a putative inhibitor of Ca2+ release from intracellular stores) did not have any significant effects on the increase of PGE2-induced by A23187. Thus, A23187 increased PGE2 through the influx of extracellular Ca2+. W7 or compound 48/80 (calmodulin inhibitors) did not alter the response of PGE2 caused by A23187. Exogenous administration of cAMP, forskolin (an activator of adenylate cyclase), or 2-chloroadenosine (a possible activator of adenylate cyclase through adenosine A2 receptor) had neither significant effects on PGE2 release nor an effect on A23187-induced increase of PGE2 release. 12-O-tetradecanoylphorbol 13-acetate (TPA, an activator of PKC) significantly stimulated PGE2 release in a dose-dependent fashion, whereas another phorbol ester with no biological activity did not. A23187 at 0.8 x 10(-6) M, but not cAMP, potentiated the TPA-induced increase of PGE2. Mepacrine (a phospholipase A2 inhibitor) reduced the A23187- and TPA-induced increase of PGE2. These results suggest that Ca2+ and protein kinase C may play important roles in the regulation of PGE2 release by cultured rabbit gastric cells.
据报道，前列腺素（PG）是胃黏膜中的重要保护因子之一。然而，内源性PG产生的调节机制尚未得到充分研究。我们研究了Ca2+、环磷酸腺苷（cAMP）和蛋白激酶C（PKC）在调节培养的兔胃黏膜细胞释放前列腺素E2（PGE2）中的可能作用。通过放射免疫测定法测量PGE2。2×10(-6)M的A23187（Ca2+离子载体）显著增加了PGE2的释放。从培养基中去除Ca2+可阻断A23187诱导的PGE2增加。TMB-8（一种推测的细胞内钙库Ca2+释放抑制剂）对A23187诱导的PGE2增加没有任何显著影响。因此，A23187通过细胞外Ca2+的内流增加了PGE2。W7或化合物48/80（钙调蛋白抑制剂）并未改变A23187引起的PGE2反应。外源性给予cAMP、福司可林（一种腺苷酸环化酶激活剂）或2-氯腺苷（一种可能通过腺苷A2受体激活腺苷酸环化酶的物质）对PGE2释放均无显著影响，对A23187诱导的PGE2释放增加也无影响。12-O-十四酰佛波醇-13-乙酸酯（TPA，一种PKC激活剂）以剂量依赖性方式显著刺激PGE2释放，而另一种无生物活性的佛波酯则无此作用。0.8×10(-6)M的A23187而非cAMP增强了TPA诱导的PGE2增加。米帕林（一种磷脂酶A2抑制剂）减少了A23187和TPA诱导的PGE2增加。这些结果表明，Ca2+和蛋白激酶C可能在调节培养的兔胃细胞释放PGE2中起重要作用。
