Kobayashi N, Russell J, Lettieri D, Sherwood L M
Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461.
Proc Natl Acad Sci U S A. 1988 Jul;85(13):4857-60. doi: 10.1073/pnas.85.13.4857.
Regulation of protein kinase C in the parathyroid gland was investigated by testing the effects of phorbol ester, exogenous phospholipase C, and low and high calcium concentrations on enzyme activity. Treatment of bovine parathyroid cells with phorbol ester, which activates protein kinase C directly, and with phospholipase C, which produces diacylglycerol, an activator of protein kinase C, significantly stimulated protein kinase C activity. Both agents also enhanced the release of parathyroid hormone. Acute exposure of bovine parathyroid cells to low extracellular calcium (0.5 mM) caused a 5- to 6-fold increase in protein kinase C activity associated with the particulate fraction. In contrast, high extracellular calcium (1.75 mM and 2.5 mM) markedly decreased membrane protein kinase C activity. These data suggest that the effects of extracellular calcium on parathyroid hormone secretion are due, at least in part, to regulation of protein kinase C activity in the parathyroid-cell membrane.
通过检测佛波酯、外源性磷脂酶C以及低钙和高钙浓度对酶活性的影响，研究了甲状旁腺中蛋白激酶C的调节机制。用能直接激活蛋白激酶C的佛波酯以及能产生二酰甘油（蛋白激酶C的激活剂）的磷脂酶C处理牛甲状旁腺细胞，可显著刺激蛋白激酶C的活性。这两种试剂还增强了甲状旁腺激素的释放。将牛甲状旁腺细胞急性暴露于低细胞外钙（0.5 mM）环境中，会使与微粒体部分相关的蛋白激酶C活性增加5至6倍。相反，高细胞外钙（1.75 mM和2.5 mM）会显著降低膜蛋白激酶C的活性。这些数据表明，细胞外钙对甲状旁腺激素分泌的影响至少部分是由于甲状旁腺细胞膜中蛋白激酶C活性的调节所致。
