Rodriguez-Commes J, Isales C, Kalghati L, Gasalla-Herraiz J, Hayslett J P
Department of Medicine, Yale School of Medicine, New Haven, Connecticut.
Kidney Int. 1994 Sep;46(3):666-74. doi: 10.1038/ki.1994.319.
Studies were performed to determine the signal transduction mechanism involved in the onset of insulin stimulated electrogenic sodium transport (Ieq) in cultured A6 cells. Insulin stimulated Ieq at a threshold concentration of one nM and a half-maximum concentration of approximately 3 nM. The onset of action occurred within 10 seconds and the increase in Ieq was augmented by pretreatment with aldosterone, similar to the action of vasopressin. Insulin stimulated an increase in Ca2+i in a dose-dependent manner that involved release from intracellular stores. Hormone stimulated Ieq was dependent on increases in Ca2+i because pretreatment with 5, 5' dimethyl BAPTA/AM blocked the increase in sodium transport. Further studies with dihydroxyclorpromazine, trifluoperazine and genistein, inhibitors of PKC, Ca2+i dependent, calmodulin dependent kinases and tyrosine kinase, respectively, suggested that the action of insulin was dependent on activation of these kinases. In contrast, insulin stimulated Ieq was independent of changes in cAMP, because insulin did not increase the accumulation of cAMP, and inhibition of adenylate cyclase with 2', 5' dideoxyadenosine did not affect transport. These results suggest that insulin, as previously shown for aldosterone, activates apical membrane amiloride sensitive sodium channels by a calcium-dependent second messenger system.
开展了多项研究以确定参与培养的A6细胞中胰岛素刺激的电生性钠转运（Ieq）起始过程的信号转导机制。胰岛素在1 nM的阈值浓度和约3 nM的半最大浓度下刺激Ieq。作用起效在10秒内发生，并且醛固酮预处理增强了Ieq的增加，这与血管加压素的作用相似。胰岛素以剂量依赖的方式刺激细胞内钙离子浓度（Ca2+i）升高，这涉及细胞内储存的钙离子释放。激素刺激的Ieq依赖于Ca2+i的升高，因为用5,5'-二甲基BAPTA/AM预处理可阻断钠转运的增加。分别用PKC抑制剂二羟基氯丙嗪、钙调蛋白依赖性激酶抑制剂三氟拉嗪和酪氨酸激酶抑制剂金雀异黄素进行的进一步研究表明，胰岛素的作用依赖于这些激酶的激活。相反，胰岛素刺激的Ieq与环磷酸腺苷（cAMP）的变化无关，因为胰岛素不会增加cAMP的积累，并且用2',5'-二脱氧腺苷抑制腺苷酸环化酶不会影响转运。这些结果表明，如先前对醛固酮所示那样，胰岛素通过钙依赖性第二信使系统激活顶端膜阿米洛利敏感钠通道。
