THURSDAY, Jan. 17, 2002 (HealthDayNews) -- Experiments with genetically engineered mice show certain receptors for the hormone estrogen play an essential role in regulating blood pressure, researchers report.
There are two classes of receptors -- called alpha and beta -- in a number of tissues, including blood vessel walls. They receive the estrogen molecule, and react by activating a variety of genes. Now, a group of American and Swedish researchers report that mice genetically engineered to lack the beta receptors develop severe high blood pressure as they age.
"These data support an essential role for estrogen receptor beta in the regulation of vascular function and blood pressure," says the study, which appears in tomorrow's issue of Science.
The study was done by a group led by Dr. Michael E. Mendelssohn, director of the Molecular Cardiology Research Institute of the New England Medical Center. His group first discovered the presence of the estrogen beta receptors in blood vessels in 1996.
"Since then, we have been working with several groups to understand what this receptor does in the cardiovascular system," he says. "This is the first demonstration that there is a clear physiological function for the estrogen receptor beta."
That function is to "regulate one or more genes that are critical for blood vessel function," Mendelssohn says. "What this work does is to make us focus our attention on what are the relevant genes that estrogen receptor beta regulates which are important to normal vascular physiology. If we can understand what the target genes are, we can" develop new drugs for hypertension.
In addition, he says, "variations or mutations in the estrogen beta gene may [affect] blood pressure control in some people." That applies to men as well as women, Mendelssohn says, since estrogen is found in both sexes. The new study was done with male mice.
The findings could lead to better treatments for hypertension, says Dr. Lori Mosca, director of preventive cardiology at the Columbia University College of Physicians and Surgeons and author of the American Heart Association position paper on estrogen and heart disease.
"It's been unclear what the role of alpha versus beta receptors is, whether the beta receptor plays a functional role, and what the functional qualities of [estrogen receptor] beta might be. This work may be helpful in targeting therapy and the creation of drugs that are specific to these receptors," she says.
However, the new research does not answer one major question for women, Mosca says.
"There is no doubt that estrogen plays a role in the vascular system," she says. "But does estrogen replacement therapy after the menopause prevent heart disease? We don't have sufficient data to answer that question."
"Clearly, we are interested in developing therapies that target receptors and that might be helpful in controlling heart disease," Mosca says. "This work might help to evolve therapy."
What To Do
The medical payoff from this new research is years away, and the standing advice on measures to control blood pressure -- proper diet, physical activity and not smoking -- are as important as ever.
For more information on high blood pressure, visit the American Heart Association or the American Society of Hypertension.
