Renal Vascular Control During Passive Heat Stress Does Not Differ Between Younger Men And Women

PURPOSE: During heatwaves, kidney injury risk is higher in younger men compared to younger women. This increased risk may be mediated, in part, by differences in renal vascular control. In a heterogenous group of men and women, we previously reported that heat stress attenuates renal vasoconstriction during a sympathetic stimulus (e.g., cold pressor test, CPT), but does not affect renal vasodilation following an oral protein load. However, it remains unknown if heat stress differentially modifies renal vascular control in men versus women. Therefore, we tested the hypothesis that renal vasoconstriction will be greater in men but vasodilation will be greater in women during passive heat stress. METHODS: Healthy, young men (n = 12) and women (n = 13, 4 ± 1 day of menstrual cycle) underwent passive heat stress (water perfused suit) in which a 0.8 °C increase in core temperature was maintained for 4.5 h. A 2-min CPT was completed 1 hour into heat stress to assess renal vasoconstriction. A whey protein shake (1.2 g of protein/kg of body weight) was ingested 1-h post-CPT to assess renal vasodilation. Blood pressure (Penaz method) was measured continually. Renal segmental artery blood velocity (BV, Doppler ultrasound) was measured before and during the CPT, and before protein and 75- and 150-min post-protein. Segmental artery vascular resistance (VR) was calculated as mean arterial pressure (MAP) divided by segmental BV. Data are presented as mean ± SD. RESULTS: Core temperature (P = 0.43) and body fluid loss (P = 0.93) did not differ between men and women. Peak increases in MAP during the CPT were greater in men (+20 ± 9 mmHg vs. +13 ± 7 mmHg, P = 0.04), but peak reductions in segmental BV (Men: -2.6 ± 3.2 cm/s, Women: -2.7 ± 2.5 cm/s, P = 0.90) or increases in segmental VR (Men: +1.4 ± 1.0 mmHg/cm/s, Women: +1.4 ± 1.2 mmHg/cm/s, P = 0.91) did not differ between men and women. MAP did not differ between men and women pre- or post-protein (P ≥ 0.06). Peak increases in segmental BV (Men: +3.6 ± 3.2 cm/s, Women: +4.0 ± 3.5 cm/s, P = 0.74) or decreases in segmental VR (Men: -0.6 ± 0.8 mmHg/cm/s, Women: -0.5 ± 0.5 mmHg/cm/s, P = 0.90) post-protein did not differ between men and women. CONCLUSIONS: Renal vasoconstrictor and vasodilator responses do not likely contribute to sex differences in kidney injury risk during heatwaves in young adults.Supported by R01OH011528