What is the central question of this study? Sympathetically-mediated vasoconstriction was previously shown to be preserved during hypoxemia in humans; however, our understanding of vascular control comes from predominantly male cohorts. We tested the hypothesis that young women attenuate sympathetically-mediated vasoconstriction during steady-state hypoxemia, whereas men do not. What is the main finding and its importance? Herein we confirm sympathetically-mediated vasoconstriction is preserved or even enhanced during steady-state hypoxia in young men and extend these data to show the peripheral vascular response to sympathetic activation during hypoxemia is attenuated in young women. These data advance our understanding of sex-related differences in hypoxic vascular control.
Activation of the sympathetic nervous system causes vasoconstriction and a reduction in peripheral blood flow. Sympathetically-mediated vasoconstriction may be attenuated during systemic hypoxia to maintain oxygen delivery; however, in predominantly male participants sympathetically-mediated vasoconstriction is preserved or even enhanced during hypoxemia. Given the potential for sex-specific differences in hypoxic vascular control, prior results are limited in application. We tested the hypothesis that young women attenuate sympathetically-mediated vasoconstriction during steady-state hypoxemia, whereas men do not. Healthy young men (n = 13, 25±4 yrs) and women (n = 11, 24±4 yrs) completed two trials consisting of a 2-min cold pressor test (CPT, a well-established sympathoexcitatory stimulus) during baseline normoxia and steady-state hypoxemia. Beat-to-beat blood pressure (BP, finger photoplethysmography) and forearm blood flow (FBF, venous occlusion plethysmography) were measured continuously. Total and forearm vascular conductance (TVC and FVC, respectfully) were calculated. A change (Δ) in TVC and FVC from steady-state during the last 1-min of CPT was calculated and differences between normoxia and systemic hypoxia were assessed. In men, the reduction in TVC during CPT was greater during hypoxia compared to normoxia (ΔTVC, p = 0.02), whereas ΔTVC did not differ between conditions in women (p = 0.49). In men, ΔFVC did not differ between normoxia and hypoxia (p = 0.92). In women, the reduction in FVC during CPT was attenuated during hypoxia (ΔFVC, p<0.01). We confirm sympathetically-mediated vasoconstriction is preserved or enhanced during hypoxemia in young men, whereas peripheral vascular responsiveness to sympathetic activation during hypoxemia is attenuated in young women. Results advance our understanding of sex-related differences in hypoxic vascular control. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

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