Booz G W, Dostal D E, Singer H A, Baker K M
Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822.
Am J Physiol. 1994 Nov;267(5 Pt 1):C1308-18. doi: 10.1152/ajpcell.1994.267.5.C1308.
Angiotensin (ANG) II has been previously shown to stimulate proliferation of neonatal rat cardiac fibroblasts via AT1 receptors. Here we conducted studies to assess involvement in this process of two second messengers linked to AT1 receptors, protein kinase C (PKC) and Ca2+. Several findings argue against a dominant role for PKC in ANG II-induced mitogenesis: 1) [Sar1]ANG II, which produced a modest, transient increase in PKC activity, was equally effective in inducing thymidine incorporation into DNA in PKC-depleted cells, whereas the effect of platelet-derived growth factor (PDGF)-BB on thymidine incorporation was reduced to the level observed with [Sar1]ANG II; 2) phorbol 12-myristate 13-acetate (PMA), a potent PKC stimulator, was ineffective in stimulating thymidine incorporation; and 3) PKC downregulation or the highly specific PKC inhibitor, compound 3, eliminated PMA-induced mitogen-activated protein (MAP) kinase activity but did not affect comparable increases induced by [Sar1]ANG II or PDGF-BB. Increased intracellular Ca2+ may be sufficient to account for [Sar1]ANG II-induced MAP kinase activity because ionomycin also increased MAP kinase activity and chelation of intracellular Ca2+ eliminated [Sar1]ANG II-induced activity in PKC-depleted fibroblasts. However, Ca2+ chelation did not prevent [Sar1]ANG II-induced MAP kinase activity in non-PKC-depleted fibroblasts. Thus ANG II can activate MAP kinase in cardiac fibroblasts by either Ca(2+)- or PKC-dependent pathways, and whereas the full effect of PDGF-BB on thymidine incorporation and cell proliferation requires a phorbol ester-sensitive PKC, the hyperplastic growth effect of ANG II does not.
血管紧张素（ANG）II先前已被证明可通过AT1受体刺激新生大鼠心脏成纤维细胞的增殖。在此，我们进行了研究，以评估与AT1受体相关的两种第二信使——蛋白激酶C（PKC）和Ca2+在这一过程中的作用。多项研究结果表明PKC在ANG II诱导的有丝分裂中并不起主要作用：1）[Sar1]ANG II可使PKC活性适度短暂增加，但其在PKC缺失的细胞中诱导胸苷掺入DNA的效果与血小板衍生生长因子（PDGF）-BB相当，而PDGF-BB对胸苷掺入的作用在PKC缺失的细胞中则降至与[Sar1]ANG II相当的水平；2）佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA），一种有效的PKC刺激剂，在刺激胸苷掺入方面无效；3）PKC下调或使用高度特异性的PKC抑制剂化合物3可消除PMA诱导的丝裂原活化蛋白（MAP）激酶活性，但不影响[Sar1]ANG II或PDGF-BB诱导的类似活性增加。细胞内Ca2+的增加可能足以解释[Sar1]ANG II诱导的MAP激酶活性，因为离子霉素也可增加MAP激酶活性，而细胞内Ca2+的螯合可消除PKC缺失的成纤维细胞中[Sar1]ANG II诱导的活性。然而，Ca2+螯合并不能阻止非PKC缺失的成纤维细胞中[Sar1]ANG II诱导的MAP激酶活性。因此，ANG II可通过Ca(2+)依赖或PKC依赖的途径激活心脏成纤维细胞中的MAP激酶，虽然PDGF-BB对胸苷掺入和细胞增殖的完全作用需要佛波醇酯敏感的PKC，但ANG II的增生性生长作用则不需要。
