Women are exposed to estrogen in several forms such as oral contraceptive pills and hormone replacement therapy. Although estrogen was believed to be cardioprotective, lately, its beneficial effects are being questioned. Recent studies indicate that oxidative stress in the rostral ventrolateral medulla (RVLM) may play a role in the development of hypertension. Therefore, we hypothesized that chronic exposure to low levels of estradiol-17β (E2) leads to hypertension in female Sprague Dawley (SD) rats potentially through generation of superoxide in the RVLM. To test this, young (3-4 months old) female SD rats were either sham-implanted or implanted (s.c.) with slow release E2 pellets (20 ng/day) for 90 days. A group of control and E2-treated animals were fed lab chow or chow containing resveratrol (0.84 g/ Kg of chow), an antioxidant. Rats were implanted with telemeters to continuously monitor blood pressure (BP) and heart rate (HR). At the end of treatment, the RVLM was isolated for measurements of superoxide. E2 treatment significantly increased mean arterial pressure (mm Hg) and HR (beats/min) compared to sham rats (119.6±0.8 vs. 105.1±0.7 and 371.7±1.5 vs. 354.4±1.3, p<0.0001 respectively). Superoxide levels in the RVLM (nmol/min*mg) increased significantly in the E2-treated group (0.833±0.11) compared to control (0.532±0.04, p<0.05). Treatment with resveratrol reversed the E2-induced increases in BP and superoxide levels in the RVLM. We conclude that chronic exposure to low levels of E2 induces hypertension and increases superoxide levels in the RVLM and that this effect can be reversed by resveratrol treatment.
- blood pressure
- oxidative stress
- Copyright © 2011, American Journal of Physiology - Regulatory, Integrative and Comparative Physiology