Influence of Age and Estradiol on Sympathetic Nerve Activity Responses to Exercise in Women

Introduction Postmenopausal women (PMW) display exaggerated increases in blood pressure (BP) during exercise, yet the mechanism(s) involved remain unclear. Moreover, research on the impact of menopausal changes in estradiol on cardiovascular control during exercise are limited. Herein, we tested the hypothesis that sympathetic responses during exercise are augmented in PMWcompared with young women (YW), and estradiol administration attenuates these responses. Methods Muscle sympathetic nerve activity (MSNA) and mean arterial pressure (MAP) were measured in 13 PMW (58 ± 1 yr) and 17 YW (22 ± 1 yr) during 2 min of isometric handgrip. Separately, MSNA and BP responses were measured during isometric handgrip in six PMW (53 ± 1 yr) before and after 1 month of transdermal estradiol (100 μg·d-1). A period of postexercise ischemia (PEI) to isolate muscle metaboreflex activation followed all handgrip bouts. Results Resting MAP was similar between PMW and YW, whereas MSNA was greater in PMW (23 ± 3 vs 8 ± 1 bursts per minute; P < 0.05). During handgrip, the increases in MSNA (PMW Δ16 ± 2 vs YW Δ6 ± 1 bursts per minute; P < 0.05) and MAP (PMW Δ18 ± 2 vs YW Δ12 ± 2 mm Hg; P < 0.05) were greater in PMW and remained augmented during PEI. Estradiol administration decreased resting MAP but not MSNA in PMW. Moreover, MSNA (PMW (-E2) Δ27 ± 8 bursts per minute versus PMW (+E2) Δ12 ± 5 bursts per minute; P < 0.05) and MAP (Δ31 ± 8 mm Hg vs Δ20 ± 6 mm Hg; P < 0.05) responses during handgrip were attenuated in PMW after estradiol administration. Likewise, MAP responses during PEI were lower after estradiol. Conclusions These data suggest that PMW exhibit an exaggerated MSNA and BP response to isometric exercise, due in part to heightened metaboreflex activation. Furthermore, estradiol administration attenuated BP and MSNA responses to exercise in PMW.