Kenyon C J, Anyaorah L, Woodburn L, Connell J M, Fraser R
MRC Blood Pressure Unit, Western Infirmary, Glasgow.
J Endocrinol. 1988 Jun;117(3):423-9. doi: 10.1677/joe.0.1170423.
The role of protein kinase C activation in the control of cortisol synthesis was studied using the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA). Bovine zona fasciculata cells were incubated with various concentrations of TPA in the presence and absence of EGTA, verapamil or nitrendipine to see whether cortisol stimulation was dependent on extra-cellular calcium ions. When free extracellular concentration of Ca2+ was reduced to approximately 10 mumol/l the cortisol response at all concentrations of TPA was reduced by approximately 25% indicating that protein kinase C activation is only partially dependent on extracellular calcium ions. This is confirmed by the effects of the voltage-dependent calcium channel blocker verapamil, which partially inhibited the cortisol response to a maximally effective concentration of TPA (1 mumol/l). However, a second channel blocker, nitrendipine, proved to be ten times more potent than verapamil and totally inhibited the TPA response. The partial effects of EGTA and verapamil and the contrast between verapamil and nitrendipine do not exclude the possibility that intracellular calcium ions are important in protein kinase C activation and may indicate that nitrendipine has better access to an additional site of inhibitory action than verapamil. It is significant that the ionophore A23187, which facilitates Ca2+ entry independently of voltage-sensitive channels, failed to overcome the inhibitory effects of nitrendipine in TPA-stimulated cells. In some other tissues, the effects of protein kinase C activation are mediated by the opening of Na+/H+ exchange ports. The involvement of this port in the cortisol response has been tested by incubating TPA- and ACTH-treated cells with amiloride, an inhibitor of Na+/H+ exchange.(ABSTRACT TRUNCATED AT 250 WORDS)
使用佛波酯12 - O -十四烷酰佛波醇-13 -乙酸酯（TPA）研究蛋白激酶C激活在皮质醇合成调控中的作用。在有和没有乙二醇双四乙酸（EGTA）、维拉帕米或尼群地平的情况下，将牛束状带细胞与不同浓度的TPA一起孵育，以观察皮质醇刺激是否依赖细胞外钙离子。当细胞外游离钙离子浓度降至约10微摩尔/升时，所有浓度TPA下的皮质醇反应降低约25%，表明蛋白激酶C激活仅部分依赖细胞外钙离子。电压依赖性钙通道阻滞剂维拉帕米的作用证实了这一点，它部分抑制了皮质醇对最大有效浓度TPA（1微摩尔/升）的反应。然而，另一种通道阻滞剂尼群地平被证明比维拉帕米的效力强十倍，并完全抑制了TPA反应。EGTA和维拉帕米的部分作用以及维拉帕米和尼群地平之间的对比并不排除细胞内钙离子在蛋白激酶C激活中很重要的可能性，并且可能表明尼群地平比维拉帕米更容易作用于另一个抑制作用位点。值得注意的是，离子载体A23187，它能独立于电压敏感通道促进钙离子进入，未能克服尼群地平在TPA刺激细胞中的抑制作用。在其他一些组织中，蛋白激酶C激活的作用是由钠/氢交换通道的开放介导的。通过用钠/氢交换抑制剂氨氯地平孵育TPA和促肾上腺皮质激素（ACTH）处理的细胞，测试了该通道在皮质醇反应中的参与情况。（摘要截断于250字）
