醛固酮-WNK4途径参与盐负荷对上皮钠通道的调节

Involvement of WNK4 in the dietary salt regulation of epithelial sodium channel through aldosterone

目的 通过建立生理条件下的盐负荷饮食大鼠模型,观察醛同酮和WNK4在水盐代谢调节中的作用.方法 将SD大鼠分为5组：高盐组（H,4%NaCl）、正常盐组（N,0.4%NaCl）、低盐组（L,0.07%NaCl）、高盐加醛固酮组（H＋A,4%NaCl＋1 mg·kg^（-1）·d^（-1）醛固酮）、低盐加螺内酯（L＋S,0.07%NaCl＋0.1 g·kg^（-1）·d^（-1）螺内酯）,所有大鼠自由饮水,喂养2周.用放射免疫法检测血浆醛同酮的变化.应用实时定量PCR和Western印迹法检测大鼠肾脏上皮钠通道γ亚基（γENaC）、WNK4的mRNA和蛋白的变化.结果 H组大鼠血浆醛同酮水平低于N组（P〈0.05）,H＋A组高于H组（P〈0.05）;L组大鼠血浆醛固酮水平高于N组（P〈0.05）,显示SD大鼠造模成功.L组大鼠肾脏γENaC蛋白表达高于N组,但是L＋S低于L组;同时H组低于N组,H＋A组高于H组,差异均有统计学意义（P〈0.05）.mRNA变化趋势和蛋白变化趋势一致.H组肾脏WNK4的蛋白表达高于N组,但是H＋A组低于H组;同时L组低于N组,L＋S组高于L组,差异均有统计学意义（P〈0.05）.mRNA的变化趋势和蛋白的变化趋势一致.结论 饮食中的盐可以调节γENaC在肾脏的蛋白表达,醛固酮和WNK4都参与了机体对盐的调节,WNK4受到醛同酮的负调节作用.

Objective To examine the role of aldosterone and WNK4 in redistribution of epithelial Na（＋） channel（~ENaC） in response to a high-sah diet. Methods 200-250 g weight Sprague-Dawley rats were randomly assigned to five groups： normal salt diet （N, 0.4% NaC1）, high salt diet （H, 4% NaCl）, low salt diet （L, 0.07% NaC1）, H treated with aldosterone （H＋A, 4% NaC1 with osmotic mini-pump at 1 mg·kg^-1·d ^-1 aldosterone）, and L treated with spironolactone （L＋ S, 0.07% NaCl with 0.1 g·kg^-1·d ^-1 spironolaetone）. Results The high salt diet decreased γENaC protein and the low salt diet increased γENaC protein. However, the γENaC of H＋A group was higher compared with that of H group and the γENaC of L＋S group was lower compared with that of L group. Radioimmunoassay demonstrated that the concentration of plasma aldosterone was decreased by high salt diet compared with that by normal salt diet. On the contrary to the aldosterone, the expression of WNK4 was remarkable enhanced in H group and decreased in L group, but it was decreased in H＋A group and enhanced in L＋S group. Conclusions The decrease of γENaC during high salt diet is regulated by aldosterone well. WNK4 kinase is affected negatively by aldosterone in kidney.