The effects of chronic unpredictable stress on renal sex steroids and renal mitochondrial function in C57Bl/6 females

Background: The kidneys play an essential role in long-term blood pressure control. Hypertension is more prevalent in males compared to females; however, this sex difference is lost once females reach menopause, suggesting a potential role for sex steroids in the pathogenesis of hypertension. Chronic stress has also been linked to the development of hypertension. Renal mitochondria are essential for normal renal function and blood pressure regulation. The impact of sex steroids on renal mitochondrial function is unclear. Understanding this relationship may yield new mechanistic insight about the pathogenesis of stress-induced hypertension. Hypothesis: Chronic stress in female mice will alter renal sex steroid profiles and impair renal mitochondrial function. Methods: To determine the effects of stress on renal sex steroids and mitochondrial function, 10–12-week-old female C57Bl/6 mice were exposed to 28 consecutive days of random unpredictable stressors at varying times of the day for varying lengths of time. Systolic blood pressure was measured via the tail cuff method on day 28 of stress. Vaginal lavage was performed at euthanasia and cytology was analyzed using hematoxylin and eosin staining to determine estrous cycle staging. Mitochondrial oxygen consumption was assessed using an Oroboros respirometer with homogenates made from the pole ends of the left kidney. Renal sex steroids were analyzed on whole right kidney homogenates using chromatography and mass spectrometry. Results: Systolic blood pressure was higher in stressed females compared to non-stressed females (in mmHg, 146±6 vs 109±11 n=4-10, p<0.01). There were no significant differences in mitochondrial respiration in stressed vs. non-stressed females overall. However, when analyzed by estrous phase, mitochondrial respiration in complexes I (in pmol O2/mg protein, 118±20 vs 70±11 n=5-6, p<0.05) and IV (329±38 vs 240±9, n=5-6, p<0.05) was lower in stressed females in the proestrus phase compared to non-stressed females in the proestrus phase. When examining renal sex steroids, testosterone was lower in stressed females compared to controls in the estrus phase (in pg/g 10.4±2.8 vs 0.4±0.4, n=4-5, p<0.01). Progesterone was lower in stressed females in each stage of the estrous cycle compared to controls (in pg/g, proestrus 13171±8464 vs 772±174, estrus 2690±1213 vs 358±117, diestrus/metestrus 1555± 328 vs 481±482, p£0.05, n=4-6). Increased blood pressure was associated with decreased renal progesterone (r= -0.78, p<0.01, n=13-14/group) and decreased renal progesterone was associated with impaired complex I function (r= 0.41, p<0.05, n=4-10/per group) in all female mice. Conclusion: These data suggest a possible mechanistic pathway for stress-induced hypertension in female mice whereby stress leads to estrous-phase dependent changes in renal sex steroid profiles that result in impaired renal mitochondrial respiration. P20GM109091, BX006218-02 (F.H.), R01HL130972-01A1, R01HL5949, BX005320-01A1, BX000168-10A1 (F.G.S.), R01 MH129798 (SKW), 1U54HL169191-01 & BX002604 (M.J.R.). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.