Sex difference in NKCC2 (bumetanide‐sensitive Na‐K‐2Cl cotransporter) and NHE3 (Na‐H exchanger type 3 ) expression – Role of estrogen

Abstract

This study examined sex differences and estrogen (E2)-mediated actions on the expression of NHE3 in whole kidney (WK) homogenates, and NKCC2 in the cortex (CTX) and outer medulla (OM) homogenates using semi-quantitative immunoblotting. NHE 3 expression was higher in intact female rats compared to weight-matched males (WK = 125±9∗, % of male, p<0.05). NKCC2 abundance was significantly higher in intact female rats in both the cortex and outer medulla (CTX = 219±20∗; OM = 133±9∗, % of male, p<0.05). Ovariectomy (OVX) abolished the NHE3 sex difference in WK (WK = 115±23, % of male, NS) and the NKCC2 sex difference in OM only (CTX = 228±16∗; OM = 91±7, % of male, p<0.05). These data suggest that ovarian hormones are responsible for the sex difference seen in NHE3 and NKCC2 expression. Next, we analyzed the E2-mediated actions on expression of NHE3 in WK and NKCC2 in CTX and OM of age-matched female rats (INTACT vs OVX vs OVX + E2 (17-□-estradiol pellet, 7 days at 2.5 □g/day)). NHE3 expression in WK (OVX = 46±7∗, OVX+E2 = 63±8∗@, % of INTACT, ∗ vs INTACT, @ vs OVX, p<0.05), and NKCC2 expression (CTX: OVX = 89±31, OVX+E2 = 28±9∗; OM: OVX = 82±8, OVX+E2 = 146±20∗ % of INTACT, ∗ vs INTACT, p<0.05) tended to decrease with OVX and returned towards INTACT levels in OVX + E2 rats in the OM only. These data indicate that E2 is in part responsible for the sex difference seen with NHE3 and NKCC2 expression. This work was supported by an NHLBI K22 award.