多巴胺对清醒血容量恒定大鼠肾上皮钠通道表达的影响

Effect of dopamine on expression of epithelial sodium channel in conscious euvolumic rats

目的:研究多巴胺对清醒血容量恒定大鼠肾上皮钠通道(ENaC)表达的影响。方法:实验动物随机分为实验组(n=29)和对照组(n=16)。在维持大鼠清醒状态下,应用伺服控制系统维持其体液恒定,实验组大鼠经静脉给予左旋多巴(5μg.kg-1.min-1),对照组大鼠给予等体积5%葡萄糖。在此期间,检测大鼠平均动脉压(MAP)、尿量、尿钠浓度及肾小球滤过率(GFR)。同时应用免疫印迹法检测肾组织ENaC3个亚单位(αENaC、βENaC和γENaC)的表达。结果:与对照组比较,实验组在给予低剂量多巴胺后大鼠平均动脉压和肾小球滤过率无明显变化(P>0.05),但尿量及尿钠浓度明显增加(P<0.05)。多巴胺并不影响αENaC和βENaC的表达,但下调γENaC的表达,与对照组比较差异有显著性(P<0.05)。结论:多巴胺在不影响血压及肾小球滤过率前提下能够引起持续的利钠利尿作用,其机制可能与其抑制γENaC表达有关。

Objective To study the effect of dopamine on the epithelial sodium channel （ENaC） in conscious euvolumic rats. Methods Animals were divided into two groups： experimental group （n= 29） and control group （n=15）. In conscious rats, the body sodium and fluid balance were constantly maintained by servo controlled replacements, and mean arterial blood pressure （MAP）, urine volume, sodium excretion and glomerular filtration rate （GFR） were determined in response to continuous dopamine infusion （5μg^-1· kg^-1·min^-1）, and the expressions of ENaC subunits （αENaC, βENaC, and γENaC） in kidney tissues were analyzed by immunoblotting method. Results Compared with control group, the MAP and GFR in experimental group did not change （P〉0.05）, but urine volume and urine sodium concentration increased significantly （P〈0.05）; the expressions of αENaC, βENaC, and γENaC did not change, but the expression of 7ENaC was decreased （P〈0.05 ）. Concluision Dopamine infusion induces a sustained natriuresis and diuresis without influence on MAP and GFR, and its mechanism may be related to down-regulation of the expression of γENaC.