Schlondorff D, DeCandido S, Satriano J A
Am J Physiol. 1987 Jul;253(1 Pt 1):C113-20. doi: 10.1152/ajpcell.1987.253.1.C113.
Angiotensin II stimulates prostaglandin (PG) E2 formation in mesangial cells cultured from rat renal glomeruli. The interactions between angiotensin II and PGE2 are important in modulating glomerular function. We examined the mechanism for stimulation of PGE2 production in mesangial cells using the putative diacylglycerol-lipase inhibitor RHC 80267 and trifluoperazine (TFP), an agent interfering with Ca2+-CaM-mediated processes. Although RHC 80267 inhibited diacylglycerol-lipase activity in mesangial cells, it did not influence PGE2 production in response to either angiotensin II or A23187. In contrast, TFP (50 microM) inhibited basal PGE2 production and stimulation by angiotensin II and A23187. TFP also decreased 14C release in response to angiotensin from cells prelabeled with [14C]arachidonic acid, which was associated with inhibition of 14C loss from phosphatidylinositol. In cells prelabeled with 32P, orthophosphate angiotensin II caused a rapid hydrolysis of phosphatidylinositol 4,5-bisphospate. TFP enhanced 32P labeling of phosphatidylinositides, but did not prevent the loss of phosphatidylinositol 4,5-bisphosphate in response to angiotensin. This was verified in cells prelabeled with myo-[3H]inositol where angiotensin stimulated formation of [3H]inositol trisphosphate. TFP enhanced formation of [3H]inositol trisphosphate both under basal- and angiotensin II-stimulated conditions. Thus TFP did not inhibit phospholipase C activation by angiotensin. Angiotensin II caused marked increases in [32P]lysophospholipids, indicating activation of also phospholipase A2. This process was inhibited by TFP. Taken together, these results are consistent with stimulation of both phospholipase C and A2 by angiotensin, the latter step responsible for the release of arachidonic acid and PGE2 formation. The activation of phospholipase A2, but not that of phospholipase C, is inhibited by TFP, perhaps by interference with calmodulin-dependent steps.
血管紧张素II可刺激从大鼠肾小球培养的系膜细胞中前列腺素（PG）E2的生成。血管紧张素II与PGE2之间的相互作用在调节肾小球功能方面很重要。我们使用假定的二酰基甘油脂肪酶抑制剂RHC 80267和三氟拉嗪（TFP，一种干扰Ca2+-钙调蛋白介导过程的药物）研究了系膜细胞中PGE2产生的刺激机制。尽管RHC 80267抑制了系膜细胞中的二酰基甘油脂肪酶活性，但它并未影响对血管紧张素II或A23187的PGE2生成反应。相反，TFP（50 microM）抑制基础PGE2生成以及血管紧张素II和A23187的刺激作用。TFP还减少了用[14C]花生四烯酸预标记的细胞对血管紧张素的14C释放，这与抑制磷脂酰肌醇的14C损失有关。在用32P、正磷酸盐预标记的细胞中，血管紧张素II导致磷脂酰肌醇4,5-二磷酸的快速水解。TFP增强了磷脂酰肌醇的32P标记，但并未阻止对血管紧张素的磷脂酰肌醇4,5-二磷酸的损失。在用肌醇-[3H]肌醇预标记的细胞中得到了验证，其中血管紧张素刺激了[3H]肌醇三磷酸的形成。TFP在基础和血管紧张素II刺激条件下均增强了[3H]肌醇三磷酸的形成。因此，TFP并未抑制血管紧张素对磷脂酶C的激活。血管紧张素II导致[32P]溶血磷脂显著增加，表明磷脂酶A2也被激活。这一过程被TFP抑制。综上所述，这些结果与血管紧张素对磷脂酶C和A2的刺激作用一致，后一步负责花生四烯酸的释放和PGE2的形成。TFP抑制了磷脂酶A2的激活，而不是磷脂酶C的激活，可能是通过干扰钙调蛋白依赖性步骤。
