Differential Effects of Sex Steroids on mRNA Expression of Renal Sodium Transporters in Mice

Abstract

Sex steroids play key roles in regulating blood pressure but their impact on renal handling of sodium is unclear. Using real‐time qt‐RT‐PCR, we investigated effects of estrogen and testosterone on the expression of renal sodium transporters in CD‐1 mice consuming 1% and 4% salt diets. Six groups (n=4) included intact female and male mice (IF & IM), ovariectomized (O) and castrated (C) mice with a placebo pellet (OP & CP), and O & C mice with a 1.5 mg estrogen or 2.5 mg testosterone pellet, respectively (OE & CT). Mice at 3 weeks old and pellets came from Harlan, Inc. and Innovative Research of America, respectively. Three days after pellet implantation, mice consumed ad libitum 1% salt diet for ten days. Four mice in each group were killed, kidneys removed, RNA extracted from 10 mg mid‐cortical sections, 1st‐strand cDNA synthesized followed by qt‐RT‐PCR using Sybr‐green and custom PCR arrays designed by Qiagen with primers of the following: NCC, NKCC, NHE2 & 3, ENaC a, b, and g, and angiotension type II receptor I (AgII‐I). Surviving mice consumed 4% salt diet for the next ten days and procedures were repeated. After the 1% salt period, we measured higher expression of AgII‐I, ENaC (a, b, g), NKCC, NCC, NHE2 & 3 from IF mice compared to IM mice (p<0.01 – 0.001), and higher expression of NCC and NHE2 in OE compared to OP (p<0.05 – 0.01). After the 4% salt period, expression of AgII‐I, ENaC (a, b, g), NKCC, NCC, NHE2 & 3 was higher in IM mice compared to the IM‐1% salt diet group (p<0.05‐0.001) with no differences between the IF 1% & IF 4% groups. Results indicate putative sex differences in the renal handling of sodium which could contribute to blood pressure regulation. Research supported by Oklahoma INBRE 8P20GM103447.