Sex Related Differences in Vasodilator Responsiveness to Hypoxia at Rest and During Exercise

Abstract

β‐adrenergic receptor activation causes a substantial portion of hypoxic vasodilation at rest and during forearm exercise. Recent evidence suggests that β‐receptors are either more sensitive or upregulated in young women vs. men. Therefore, we examined whether sex influences hypoxic vasodilation in 31 subjects (15F/16M; 26± 1 yr). We also examined whether potential sex related differences existed in a group of older adults (6F/5M; 61± 2 yr). All subjects performed forearm exercise at 10% and 20% of maximum under normoxic and hypoxic (80% arterial O2 saturation) conditions. Forearm vascular conductance (FVC; ml/min/100 mmHg) was calculated from blood flow (ml/min) and blood pressure (mmHg). At rest young females demonstrated a greater vasodilator response to hypoxia compared to men (39 ± 12% vs. 13 ± 6%, P < 0.05). The compensatory vasodilator response to hypoxia exercise (% change in ΔFVC compared to respective normoxic exercise trial) was also greater in young womenat 10% (46 ± 8% vs. 29 ± 5%, P < 0.05) and 20% exercise (38 ± 6% vs. 23 ± 4%, P < 0.05). Interestingly the compensatory vasodilator responses between older women and men were similar at 10% (28 ± 6% vs. 28 ± 10%, P = 0.99) and 20% exercise (13 ± 6% vs. 15 ± 7%, P = 0.84), respectively. Our data suggest that the compensatory vasodilator response to hypoxic exercise is greater in young women compared to men. However, sex specific differences appear to be lost with aging.