Estrogen appears to improve kidneys' ability to shed sodium, study says
FRIDAY, Feb. 6 (HealthDay News) -- Hormones and a cell receptor in the kidneys may explain why premenopausal women have fewer problems than men with salt-sensitive hypertension, a new study says.
Salt-sensitive hypertension occurs when the kidneys hold onto more sodium than necessary. This drives up blood pressure as the body tries to force the kidneys to get rid of excess salt. Endothelin B (ETB) receptors, found in the blood vessels and tubules of the kidney, are thought to act as gatekeepers, deciding how much salt the body should excrete.
"We know from other studies we have done that this endothelin B receptor is critical to keeping you from becoming hypertensive when you eat salt," investigator Dr. David Pollock, a renal physiologist in the Vascular Biology Center at the Medical College of Georgia, said in a news release issued by the university.
However, endothelin A (ETA) receptors counteract their siblings' work by signaling when to increase blood pressure. ETA antagonist drugs, which block the receptors, are already used to control pulmonary hypertension.
Tests on rats showed ETA receptors do not reduce blood flow to the kidneys in female rats as much as they do to male rats. Instead, they actually increase sodium output without increasing blood pressure.
When researchers removed the ovaries of the female rats, they responded more like the males. Estrogen, Pollack said, appeared to improve the action of the ETA receptors.
The findings were published in the February issue of Hypertension.
The researchers plan more studies into different receptor subtypes. Meanwhile, colleagues at the University of Edinburgh in Scotland have begun studying how ETA receptor blockers may impact sodium excretion.
The American Heart Association has more about hypertension.
-- Kevin McKeever
SOURCE: Medical College of Georgia, news release, Jan. 28, 2009
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