Low Salt Diet Elevates Aldosterone Levels and Induces Endothelial Impairment in a Sex‐and Strain‐Dependent Manner in Mice

Our previous work indicates that high salt diet fails to suppress plasma aldosterone in female Balb/C mice, in contrast to males, which reflects clinical data in women. Balb/C female mice also develop sex‐specific, high salt‐induced endothelial dysfunction, which is ablated by mineralocorticoid receptor (MR) antagonism. In contrast, other reports indicate C57Bl6 female mice suppress aldosterone production and do not develop sex‐specific endothelial impairment on high salt, indicating strain‐dependent effects of salt on aldosterone production and endothelial function in female mice. We hypothesized that low salt diet will more pronouncedly increase plasma aldosterone and induce endothelial impairment in female Balb/C mice compared to male Balb/C or C57BL6 female mice. Male and female Balb/C (n=5) and C57Bl6 mice (n=5–12) were fed a normal (NS, 0.4% NaCl) or low salt (LS, 0.05% NaCl) diet for 28 days. LS increased plasma aldosterone level in female Balb/C (1435±52 LS BalbC vs 375±104 NS BalbC pg/ml, 3‐way ANOVA, *P<0.05) and C57BL6 mice (677±124 LS C57 vs 204±43 NS C57 , *P<0.05). LS increased aldosterone levels in Balb/C male mice (913±176 LS BalbC vs 265±96 NS BalbC , *P<0.05), however, not in C57BL6 mice (397±95 LS BalbC vs 220±55 NS BalbC ). Aldosterone levels of both male and female Balb/C mice on LS were significantly higher than those of their same‐sex C57BL6 counterparts (*P<0.05). These data indicate an additive effect of both female sex and Balb/C strain to potentiate aldosterone production in response to LS stimulus. Endothelial‐dependent aorta relaxation responses to acetylcholine were impaired by LS in Balb/C female mice, but not in Balb/C male mice (2‐way ANOVA with repeated measures, *P<0.05). In contrast, neither male nor female C57BL6 mice developed endothelial impairment in response to LS. Relaxation responses to acetylcholine in the presence of LNAME indicated that reduced nitric oxide activity mediates endothelial impairment in Balb/C female mice. Neither constriction responses to phenylephrine nor endothelial‐independent relaxation to sodium nitroprusside were altered between any groups. Therefore, LS induces endothelial impairment only in female Balb/C mice. We and others have previously shown a crucial role for endothelial MR in endothelial dysfunction in females. Our qRT‐PCR analysis demonstrated a sex‐difference in endothelial MR mRNA expression favoring a higher level in females of both Balb/C and C57Bl6 mice. However, both male (5.2±1.3‐fold change from NS C57 , 1‐way ANOVA, *P<0.05) and female (12.8±3.7, *P<0.05) Balb/C mice demonstrated a higher endothelial MR expression level than their same‐sex C57BL6 counterparts. Collectively, these data indicate that female Balb/C strain potentiates sex‐specific increases in aldosterone levels and endothelial impairment on LS, the latter of which may be mediated by increased endothelial MR expression. These data add evidence that the Balb/C mouse is a clinically relevent model of aldosterone‐induced endothelial impairment in females, which reflects the association of aldosterone and endothelial dysfunction in women. Support or Funding Information 1R01HL130301‐01, 19EIA34760167, Adrenal Center pilot grant, 1K99HL146948‐01A1