Regional cutaneous vasodilatory responses to local heating in post-menopausal females with and without hormone replacement therapy

We investigated whether post-menopausal females receiving hormone replacement therapy (HRT) exhibit greater nitric oxide (NO)-dependent cutaneous microvascular responses than those not receiving HRT, assessed via pharmacological NO synthase (NOS) inhibition during local heating. We also examined regional differences in microvascular response between and within groups. Twenty-one post-menopausal females (10 receiving HRT, 11 not receiving HRT) underwent assessment of cutaneous vascular conductance (CVC), expressed as a percentage of maximum vasodilation (%CVCmax), at the chest, abdomen, forearm, and calf using laser-Doppler flowmetry. Local skin temperature was raised from 33°C to 42°C for ~30 min, followed by ~40 min perfusion with 20 mM NG-nitro-L-arginine methyl ester (L-NAME; NOS inhibitor) using intradermal microdialysis. The NO contribution to vasodilation was defined as the difference in %CVCmax between the 42°C and L-NAME plateau. There were no significant differences in the NO contribution to vasodilation between groups or between sites within groups (all P > 0.107). During baseline, females not receiving HRT demonstrated 7.6 [0.8, 14.4]% higher %CVCmax at the forearm compared with abdomen (P = 0.021). During the 42°C heating plateau, this group also showed abdominal %CVCmax values that were 11.8 [0.04, 23.5]% lower than the calf (P = 0.041) and 12.7 [1.1, 24.4]% lower than the forearm (P = 0.025). Females receiving HRT demonstrated 12.0 [2.4, 21.5]% greater abdominal %CVCmax than those not receiving HRT (P = 0.014). Altogether, our findings indicate that HRT is not associated with NO-dependent cutaneous vasodilation during local heating in post-menopausal females but is associated with regional heterogeneity in cutaneous vasodilatory responses.