Bodart V, Ong H, De Léan A
Department of Pharmacology, Faculty of Medicine, Université de Montréal, Canada.
J Steroid Biochem Mol Biol. 1995 Jul;54(1-2):55-62. doi: 10.1016/0960-0760(95)00077-d.
Stimulation of aldosterone synthesis in bovine adrenal zona glomerulosa (ZGB) cells by angiotensin II (AngII) is believed to be mediated by the phospholipase C (PLC) pathway that results in the increase of cytosolic free calcium concentration and in the activation of protein kinase C (PKC). However, the cell proliferation and contraction associated with AngII action are known to be mediated in part by protein tyrosine kinases (PTK). To assess the potential role of PTK in the stimulatory effect of AngII on adrenal steroidogenesis, the actions of a series of PTK inhibitors on this metabolic pathway were examined in isolated ZGB cells. Tyrphostin 23 (TP23) caused a dose-dependent inhibition of AngII-stimulated aldosterone production with an IC50 of 15 microM and reached complete inhibition at 100 microM. Genistein (GS) was more potent with an IC50 of 35 nM and complete inhibition at 10 microM. The stimulation of aldosterone production by the calcium-mobilizing agent thapsigargin (Thaps) was also dose-dependently inhibited by TP and GS with the same potency. A specific PKC inhibitor, calphostin C (0.1 microM) caused only a 51.7% inhibition of AngII-stimulated aldosterone production. In the same way, a specific Ca2+/calmodulin-dependent protein kinase inhibitor, KN-62 (1 microM), reduced aldosterone production stimulated by AngII by 64%. As expected, thapsigargin-stimulated aldosterone biosynthesis was not affected by calphostin C, but was completely inhibited by KN-62. These results demonstrate for the first time that protein tyrosine kinase activity is part of the angiotensin II signalling pathway in bovine zona glomerulosa cells. The activation of this PTK occurs subsequently to the mobilization of intracellular calcium. This calcium-dependent protein tyrosine kinase pathway is essential for the steroidogenic response to AngII in bovine zona glomerulosa cells.
血管紧张素II（AngII）对牛肾上腺球状带（ZGB）细胞醛固酮合成的刺激作用被认为是由磷脂酶C（PLC）途径介导的，该途径导致胞质游离钙浓度升高并激活蛋白激酶C（PKC）。然而，已知与AngII作用相关的细胞增殖和收缩部分是由蛋白酪氨酸激酶（PTK）介导的。为了评估PTK在AngII对肾上腺类固醇生成的刺激作用中的潜在作用，在分离的ZGB细胞中研究了一系列PTK抑制剂对该代谢途径的作用。酪氨酸磷酸化抑制剂23（TP23）对AngII刺激的醛固酮生成产生剂量依赖性抑制，IC50为15微摩尔，在100微摩尔时达到完全抑制。染料木黄酮（GS）更有效，IC50为35纳摩尔，在10微摩尔时完全抑制。钙动员剂毒胡萝卜素（Thaps）对醛固酮生成的刺激也被TP和GS以相同效力剂量依赖性抑制。一种特异性PKC抑制剂，钙泊三醇C（0.1微摩尔）仅对AngII刺激的醛固酮生成产生51.7%的抑制。同样，一种特异性钙/钙调蛋白依赖性蛋白激酶抑制剂，KN-62（1微摩尔）使AngII刺激的醛固酮生成减少64%。正如预期的那样，毒胡萝卜素刺激的醛固酮生物合成不受钙泊三醇C影响，但被KN-62完全抑制。这些结果首次证明蛋白酪氨酸激酶活性是牛球状带细胞中血管紧张素II信号通路的一部分。这种PTK的激活发生在细胞内钙动员之后。这种钙依赖性蛋白酪氨酸激酶途径对于牛球状带细胞中对AngII的类固醇生成反应至关重要。
