Sex differences observed in forearm exercise vasodilation are not mediated through differences in nitric oxide or prostaglandin signaling (1106.3)

Abstract

We hypothesized exercise vasodilation in skeletal muscle differs between sexes due to nitric oxide synthase (NOS) and cyclooxygenase (COX) signalling. 39 healthy adults (19 females, F, 20 males, M, 26 ± 1 yrs) completed two 10‐min bouts of dynamic forearm exercise at 15% effort, separated by 20 min rest. After 5 min of control exercise, NOS or COX was inhibited during the final 5 min of exercise by intra‐arterial infusion of L‐NMMA or ketorolac, respectively. During min 5‐10 of the second exercise bout the remaining drug was infused to achieve double blockade (DB). Forearm blood flow (FBF; echo and Doppler ultrasound), arterial pressure (brachial catheter), and forearm lean mass (DEXA) were measured to calculate relative forearm vascular conductance (FVC) = FBF/100mmHg/100g lean mass. Results are mean ± SE. Females exhibited greater vasodilation than Males in control exercise (Δ FVC, 19±1 vs. 14±1, P < 0.01). L‐NMMA reduced FVC similarly (F: Δ ‐2.3 ± 1.3 vs. M: Δ – 3.7 ± 0.8, p = 0.85). In contrast, ketorolac increased FVC similarly in Females and Males (F: Δ 2.1 ± 1.3 vs. M: Δ 2.2± 1.9, p = 0.83). Despite Females exhibiting a greater exercise FVC, DB caused similar Δ FVC between the sexes (0.89). Females have a greater exercise vasodilatory response. NOS, COX, and DB responses are similar, thus, exercise vasodilation differences between sexes are due to a NOS‐COX independent mechanism(s). Grant Funding Source: Supported by NIH 144PRJ52FK