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首页> 外文期刊>American Journal of Physiology >Chronic exposure to TPA depletes PKC alpha and augments Ca-dependent insulin secretion from cultured rat islets.
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Chronic exposure to TPA depletes PKC alpha and augments Ca-dependent insulin secretion from cultured rat islets.

机译：长期暴露于TPA会耗尽PKCα，并增加培养的大鼠胰岛中Ca依赖性胰岛素的分泌。

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摘要

The insulin secretory responses of rat islets to glucose (15 mM), 12-O-tetradecanoylphorbol 13-acetate (TPA; 500 nM), and potassium (30 mM) were determined from perifused islets cultured for 22-24 h in CMRL-1066 medium (control cultured) or islets cultured in the additional presence of 500 nM TPA. Islet content of protein kinase C alpha (PKC alpha) and serine and threonine phosphoprotein patterns were also monitored after the culture period. Compared with freshly isolated islets, culturing alone had no adverse effect on the capacity of TPA or 30 mM potassium to stimulate secretion or on the islet content of PKC alpha. In agreement with previous studies, culturing in TPA reduced the islet content of immunoreactive PKC alpha by > 95% and abolished the capacity of the phorbol ester to stimulate secretion during a subsequent dynamic perifusion. Culturing in TPA slightly improved the insulin secretory response to 15 mM glucose compared with control-cultured islets; however, sustained rates of 15 mM glucose-induced secretion from these islets were significantly less than the responses of freshly isolated islets. Islets cultured in TPA responded to 30 mM potassium with a markedly amplified insulin secretory response that was abolished by nitrendipine. Enhanced phosphorylation of several islet proteins was also observed in TPA-cultured islets compared with control-cultured islets. These findings demonstrate that culturing alone impairs glucose-induced secretion, a response that is improved but still subnormal compared with freshly isolated islet responses, if TPA is included in the culture medium. Sustained phosphorylation of several islet proteins in TPA-cultured islets may account, at least in part, for augmented calcium-dependent secretion.
机译：从在CMRL-1066中培养22-24小时的融合胰岛确定大鼠胰岛对葡萄糖（15 mM），12-O-十四烷酰佛波醇13-乙酸盐（TPA; 500 nM）和钾（30 mM）的胰岛素分泌反应培养基（对照培养）或在500 nM TPA额外存在下培养的胰岛。培养期后也监测蛋白激酶Cα（PKCα）的胰岛含量以及丝氨酸和苏氨酸磷蛋白的模式。与新鲜分离的胰岛相比，单独培养对TPA或30 mM钾刺激分泌的能力或PKCα的胰岛含量没有不利影响。与之前的研究一致，在TPA中进行培养可将免疫反应性PKCα的胰岛含量降低95％以上，并消除佛波酯在随后的动态灌注期间刺激分泌的能力。与对照培养的胰岛相比，TPA的培养稍微改善了对15 mM葡萄糖的胰岛素分泌反应;然而，这些胰岛的15 mM葡萄糖诱导的分泌持续速率显着低于新鲜分离的胰岛。在TPA中培养的胰岛对30 mM钾有反应，其胰岛素分泌反应明显增强，尼群地平消除了该反应。与对照培养的胰岛相比，在TPA培养的胰岛中还观察到几种胰岛蛋白的磷酸化增强。这些发现表明，单独培养会损害葡萄糖诱导的分泌，如果在培养基中包含TPA，则与新鲜分离的胰岛反应相比，这种反应虽然有所改善，但仍不正常。 TPA培养的胰岛中几种胰岛蛋白的持续磷酸化至少可以部分解释钙依赖性分泌增加的原因。

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