Microvascular arteriolar reactivity in response to skeletal muscle contractions in female and male hamsters.

Microvascular control mechanisms involved in the blood flow response to muscle contractions have been well documented in males but remain poorly understood in females. Therefore, we characterized arteriolar vasodilation in situ using intravital microscopy of the retractor muscle of anesthetized female and male hamsters (8-13 weeks). Arterioles were stimulated physiologically by contracting 3-5 skeletal muscle fibers overlying the arteriole for 2 min using a range of twitch and tetanic stimulation parameters: 6, 15, and 60 contractions per minute (cpm) at 20 Hz, or 4, 20, and 70 Hz at 15 cpm (250 ms train duration) and pharmacologically via 2 min micropipette application of nitric oxide (NO, 10-5 M), adenosine (ADO, 10-6 M) and potassium (K+, 20 mM) as well as acetylcholine (ACh, 10-6 M) to assess local and conducted responses. Sex differences were not observed in the magnitude or rate of arteriolar vasodilation under any physiological or pharmacological condition. Collectively, these data demonstrate that arteriolar reactivity to muscle contractions and to pharmacological stimuli relevant to muscle contractions, were not different between females and males. These data suggest that the integrated vascular response during active hyperemia may not be sexually dimorphic.