Wilson S P
Department of Pharmacology, School of Medicine, University of South Carolina, Columbia 29208.
J Biol Chem. 1990 Jan 15;265(2):648-51.
Bovine adrenal chromaffin cells were exposed to phorbol esters to determine the effects of reduced levels of protein kinase C on secretion of hormones. Treatment with active phorbol esters such as 4 beta-phorbol 12, 13-didecanoate (PDD) reduced levels of protein kinase C activity with a maximal 80-90% reduction in activity after 16-24 h treatment (greater than or equal to 500 nM PDD). Treatment with PDD also inhibited catecholamine secretion from chromaffin cells evoked by nicotine, barium, and scorpion venom (50-70%, t1/2 approximately 6 h) and by veratridine (80%, t1/2 less than 15 min). Secretion induced by these agents in phorbol ester-treated cells returned to that of untreated cells by 3-4 days despite no recovery of protein kinase C activity. Potassium-evoked secretion was not inhibited by phorbol ester treatment. Catecholamine secretion from digitonin-permeabilized cells was more sensitive to calcium between 1 and 24 h, but not greater than or equal to 48 h, after addition of phorbol ester. The results suggest that phorbol esters inhibit secretion by activation of protein kinase C resulting in inhibition of ion channels or receptors but not of the secretory machinery itself; hence, protein kinase C may usually machinery itself; hence, protein kinase C may usually attenuate secretory responses in the adrenal chromaffin cell.
将牛肾上腺嗜铬细胞暴露于佛波酯中，以确定蛋白激酶C水平降低对激素分泌的影响。用活性佛波酯如4β-佛波醇12,13-十二烷酸酯（PDD）处理可降低蛋白激酶C活性水平，在16 - 24小时处理后（≥500 nM PDD）活性最大降低80 - 90%。用PDD处理还可抑制尼古丁、钡和蝎毒（50 - 70%，t1/2约6小时）以及藜芦碱（80%，t1/2小于15分钟）诱发的嗜铬细胞儿茶酚胺分泌。尽管蛋白激酶C活性未恢复，但这些药物在佛波酯处理细胞中诱导的分泌在3 - 4天内恢复到未处理细胞的水平。钾诱发的分泌不受佛波酯处理的抑制。在添加佛波酯后1至24小时，但不超过48小时，洋地黄皂苷通透细胞的儿茶酚胺分泌对钙更敏感。结果表明，佛波酯通过激活蛋白激酶C来抑制分泌，从而导致离子通道或受体的抑制，但不抑制分泌机制本身；因此，蛋白激酶C通常可能会减弱肾上腺嗜铬细胞中的分泌反应。
