New study suggests link between chronic estrogen exposure and high blood pressure

The study is entitled Chronic Estradiol-17β Exposure Increases Superoxide Production in the Rostral Ventrolateral Medulla (RVLM) and Causes Hypertension: Reversal by Resveratrol." It appears in the Articles in PresS section of the American Journal of Physiology – Regulatory, Integrative, and Comparative Physiology, published by the American Physiological Society.

Methodology

The researchers looked to the rostral ventrolateral medulla (RVLM), a critical region in the brain stem known to be involved with the maintenance of blood pressure and thought to be associated with hypertension and heart failure. They theorized that chronic exposure to low levels of estrogen (in the form of estradiol-17β, also called E2) could influence this area of the brain. They hypothesized that E2 exposure could increase the anti-oxidant superoxide, which causes stress in the body and the RVLM to respond by increase the body's blood pressure. They also wanted to examine whether or not resveratrol, the anti-oxidant that has a strong beneficial impact on the brain, would have a positive effect on superoxide and blood pressure activity.

To test their hypotheses they conducted a two-phase experiment using rats. In phase 1, animals were divided into groups and used as either controls or implanted with E2. After 90 days of E2 exposure the animals were examined and key data collected. In phase 2, the animals were used as either controls or implanted with E2 and, in addition, fed resveratrol-laced chow for 90 days. As with phase 1, RVLM was subsequently isolated from each animal and examined for increases in superoxide, hypertension and other key health markers.

Results

The researchers found that chronic E2 exposure caused a significant increase in superoxide in the RVLM, and in blood pressure. In addition they determined that the increases in both indicators were reversed with resveratrol. Taken together, the findings demonstrate that chronic exposure to low levels of E2 is capable of causing hypertension, possibly by increasing superoxide generation in the RVLM.

Importance of the Findings

In an interview, lead study author Dr. P.S. MohanKumar said, "This is an important study on at least two levels. First, it continues to confirm the negative effect that long-term estrogen exposure has for females. Second, it provides a new rationale for how and why this relationship occurs."

Dr. MohanKumar continued, "Because so many women use estrogen-only HRT to combat the effects of menopause, it is imperative that we better understand the risks that chronic exposure has for females and why these effects occur. In studies such as this we come one step closer to clarifying the relationship and have established a launch pad for identifying how the process might be interrupted in the future."

More information: ajpregu.physiology… ull.pdf+html

Provided by American Physiological Society