Sex differences in renal acid-base regulation

Abstract

Transport along the renal tubule differs between female and male rodents, possibly as a consequence of varying abundance and expression of transporters along the nephron. For several aspects such as renal Na+ transport and blood pressure regulation, this has been comprehensively studied; however, data on sex differences in renal acid-base regulation are less well understood. We hypothesized that there will be sex differences in transporter expression profiles in response to acid-base challenges. We used female and male C57Bl/6 mice (n=10 per sex and treatment), which were challenged by acid (NH4Cl, 0.28 mM) and base (NaHCO3, 0.28 mM) in drinking water for 8 days. Blood and urine samples were collected at baseline and at the end of the experimental period before kidneys were harvested under isoflurane anesthesia. Data were analyzed by 2-way ANOVA followed by Tukey multiple comparisons test. In response to NH4Cl challenge, urine pH significantly decreased in both sexes without sex differences (male baseline: 6.4±0.1 vs. NH4Cl: 5.7±0.1; female baseline: 6.2±0.2 vs NH4Cl: 5.6±0.1). In contrast to the urinary response, blood pH was not significantly affected in male mice (male baseline: 7.29±0.01 vs. NH4Cl: 7.26±0.02); however, significantly decreased in female mice (female baseline: 7.28±0.01 vs NH4Cl: 7.22±0.02). Despite differences in acid-base physiology, no differences were observed in the abundance of NHE3, pS552-NHE3, Npt2a, NKCC2, NCC, pT58-NCC or pendrin between sexes. In response to NaHCO3 challenge, urine pH significantly increased in both sexes; however, the increase was significantly smaller in female vs. male mice (male baseline: 6.3±0.1 vs. NaHCO3: 7.6±0.1; female baseline: 6.3±0.1 vs NaHCO3: 7.0±0.3). In contrast to the urinary response, blood pH significantly increased in male mice (male baseline: 7.28±0.01 vs. NaHCO3: 7.40±0.01); however, was not significantly affected in female mice (female baseline: 7.29±0.01 vs NaHCO3: 7.31±0.01). These differences in females compared to males were associated with a significantly greater abundance of Npt2a (~1.5-fold), pendrin (~1.4-fold) and H-ATPase (~1.5-fold). No differences were observed in the abundance of NHE3, pS552-NHE3, NKCC2, NCC, pT58-NCC, between sexes. In summary, our study demonstrates that acid-base regulation shows very specific sex differences: (i) female mice seem to be more prone to a NH4Cl disturbance compared with male mice, (ii) acid challenges under these conditions do not result in major changes in the abundance of the tested proteins, (iii) male mice are more prone to a NaHCO3 disturbance possibly because of (iv) lower abundances of Npt2a, pendrin and H-ATPase. This work was supported by a VA Merit Review Award IBX004968A (to Dr. Rieg) and a Pilot Project from the USF Microbiomes Institute (to T.R. and J.D.R). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.