Abstract
An exaggerated pressor response to exercise is associated with increased risk of cardiovascular events. The exercise pressor reflex, comprised of metabolic and mechanically sensitive skeletal muscle afferents, contributes importantly to blood pressure control during exercise. Data in preclinical animal models suggest that estradiol (E2) attenuates the pressor responses to exercise pressor reflex activation, yet it remains unclear if these findings translate to humans. Accordingly, we tested the hypothesis that pressor responses during exercise are augmented in post-menopausal women (PMW) compared to young women (YW), and that E2 administration will attenuate these responses in PMW. Methods: Mean arterial pressure (MAP, Finometer) and heart rate (ECG) were continuously measured in 12 PMW (age 59±2 years) and 16 YW (age 22±1 years) during 2-min of isometric handgrip performed at 30% of maximal voluntary contraction (MVC). Handgrip was immediately followed by 3-min of post-exercise ischemia (PEI), which isolates the muscle metaboreflex. Separately, BP responses during isometric handgrip at 35% MVC and PEI were measured in 6 PMW (age 53±1 years) before and after 1 month of transdermal E2 administration (100 μg/day). Results: Resting MAP was similar between PMW (77±3 mmHg) and YW (80±3 mmHg; P >0.05). During handgrip, the increase in MAP was greater in PMW (Δ20±2mmHg) compared to YW (Δ12±1 mmHg; P <0.05), and this was maintained during PEI (Δ14±1 mmHg PMW vs. Δ9±1 mmHg YW; P <0.05). Estradiol administration decreased resting BP in PMW (MAP 93±3 mmHg vs. 89±3 mmHg; P <0.05). Moreover, the increase in MAP during exercise in PMW was attenuated following estradiol administration (Δ31±8 mmHg vs. Δ20±6 mmHg; P <0.05). There was also a tendency for this reduction in MAP during PEI (Δ22±6 mmHg vs. Δ18±7 mmHg; P =0.08). Conclusions: These preliminary data suggest that PMW exhibit an exaggerated BP response to isometric exercise, due in part to heightened metaboreflex activation, and that estradiol administration can attenuate such responses.
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