多巴胺D_4受体对肾脏近曲小管上皮细胞胰岛素受体表达和功能的影响

Effect of D_4 Dopamine Receptor on Insulin Receptor Expression and Function in Renal Proximal Tubule Cells

目的研究多巴胺D4受体对肾脏近曲小管上皮(RPT)细胞胰岛素受体表达和功能的影响。方法以RPT细胞株为研究对象,采用免疫印迹法测定D4受体激动剂PD168077刺激D4受体后胰岛素受体的表达变化,并探讨其作用机制。结果D4受体激动剂PD168077(10-7mol/L,24 h)可明显抑制WKY大鼠RPT细胞胰岛素受体的表达,该作用呈现浓度和时间依赖性关系。PD168077对胰岛素受体表达的抑制作用可被D4受体特异性拮抗剂L745870(10-6mol/L)所阻断。与单用胰岛素相比,在PD168077(10-7mol/L,24 h)预先刺激的情况下,胰岛素对Na+-K+-ATP酶活性的刺激作用降低了39%(P<0.05)。钙离子通道阻断剂尼卡地平(10-7mol/L)可以阻断PD168077对RPT细胞胰岛素受体的抑制作用。结论D4受体对胰岛素受体蛋白表达和功能具有抑制作用,此作用可能通过钙离子通道发挥影响。

Objective To investigate the effect of D4 dopamine receptor on insulin receptor expression and function in renal proximal tubule （RPT）. Methods Immortalized RPT cells from Wistar-Kyoto （WKY） was used in the study and stimulated by D4 dopamine receptor agonist PD168077. Insulin receptor expression was determined by immunoblotting. The function of insulin receptor was determined by measurement of the Na^＋-K^＋ -ATPase activity. Results D4 dopamine receptor decreased insulin receptor protein expression in a concentration- and time-dependent manner in WKY RPT cells. Insulin increased the Na^＋-K^＋-ATPase activity in WKY RPT cells. Pretreat- ment with PD168077 inhibited the stimulatory effect of insulin. Moreover, the effect was blocked in the presence of D4 dopamine receptor antagonist L745870 （10 6 tool/L） or calcium channel blocker nicardipine （10 7 mol/L）. Conelusion Stimulation of D4 dopamine receptor decreases insulin receptor expression in WKY RPT cells; the calcium channel is involved into the pathophysiological action.