Loss of WNK3 is compensated for by the WNK1/SPAK axis in the kidney of the mouse

WNK3 kinase is expressed throughout the nephronand acts as a positive regulator of NKCC2 and NCC in vitro. Here we addressed the in vivo relevance of WNK3 using WNK3-deficient mice. WNK3−/− mice were viable and showed no gross abnormalities. The net tubular function was similar in wild-type (WT) and WNK3−/− mice as assessed by determination of 24-h urine output (1.63 ± .06 in WT and 1.55 ± .1 ml in WNK3−/−, n=16; P=0.42) and ambient urine osmolarity (1,804 ± 62 in WT vs. 1,819 ± 61 mosmol/kg in WNK3−/−, n=40; P=0.86). Water restriction (48 h) increased urine osmolarity similarly in both genotypes to 3,440 ± 220 and 3,200 ± 180 mosmol/kg in WT and WNK3−/− mice, respectively (n=11; P=0.41). The glomerular filtration rate (343 ± 22 vs. 315 ± 13 ml/min), renal blood flow(1.35 ± 0.1 vs. 1.42 ± 0.04 ml), and plasma renin concentration (94 ± 18 vs. 80 ± 13 ng ANG I·ml−1·h−1) were similar between WT and WNK3−/− mice (n=13; P=0.54). WNK1was markedly upregulated in WNK3-deficient mice, whereas the expression of ...