Sexual dimorphic regulation of NCC involves higher SPAK and NCC phosphorylation in female rodents

Abstract

It is known that NCC expression/function is subject to sexual dimorphic regulation and that estradiol administration enhances NCC expression in the distal convoluted tubule apical membrane of ovariectomized rats. To begging to elucidate the mechanisms involved, we analyzed the NCC activity, as well as the NCC and phospho‐T58 NCC expression in total and membrane fraction proteins, and total SPAK and phospho‐S383‐SPAK in total proteins, using specific antibodies, in proteins extracted from kidneys of wild type mice and normal or gonadectomized male and female rats, four weeks after sham or gonadectomy. Serum radioimmunoanalysis at four weeks confirmed the absence of sex hormones. In normal rats, the urinary response to bendroflumethiazide was higher in female than in male rats. No difference was observed in total or membrane NCC expression. However, phospho‐T58‐NCC was significantly higher in female than in male rats. This was associated with increased expression and S383 phosphorylation of SPAK in female than in male rats. Interestingly, the differences were eliminated by ovariectomy. No effect of orquiectomy on NCC and SPAK expression/phosphorylation was observed. In mice we observed that both, total and phospho‐T58‐NCC expression were significantly higher in female than in male animals. We conclude that increased activity of NCC in female rats is due to increased phosphorylation of NCC.