"Estrogen seems to exert protective actions on heart performance that may be independent from any changes in blood pressure," said Groban.
Chappell led a project to determine if estrogen is also protective against the hypertension and renal damage that arises from excess salt in the diet. In the rats fed a high salt diet, estrogen depletion increased blood pressure and exacerbated renal injury. The lack of estrogen resulted in increase levels of a hormone called aldosterone that may contribute to both diastolic dysfunction and kidney injury.
"This seems to go hand in hand with studies published recently showing that blocking aldosterone is protective to the heart and kidneys irrespective of its effects on blood pressure," said Chappell, an associate professor in the School of Medicine, which is part of Wake Forest University Baptist Medical Center.
In the third project, the scientists found that estrogen depletion results in marked increases in blood pressure, which they hope will help them understand why a woman's chances of getting high blood pressure increase considerably after menopause. Led by Liliya Yamaleyeva, M.D., the researchers measured nitric oxide, a hormone that has been found to relax blood vessels and lower blood pressure.
Three different enzymes are involved in nitric oxide formation and the researchers found that estrogen depletion augments one of the enzymes, but markedly reduces one of the others.
"We conclude that one of the nitric oxide enzymes may be an important mechanism that causes blood pressure to increase after estrogen depletion," said Yamaleyeva.
The development of an animal that is sensitive to estrogen's effects is significant because most human and animal hypertension research has focused on males. The rats are also sensitive to salt, which will help
'"/>
Contact: Karen Richardson
krchrdsn@wfubmc.edu
336-716-4453
Wake Forest University Baptist Medical Center
22-Sep-2005