Researchers may have found why women have an edge on salt-sensitive hy...(tween what is consumed and excreted. Sal...)

Date:1/28/2009

tween what is consumed and excreted. Salt-sensitive hypertension means kidneys hold onto too much salt. When the kidneys realize the blood pressure is getting too high they try to get rid of salt. If they can't, in an ironic twist, blood pressure goes even higher to help literally force salt out of the kidneys. That approach eventually works but over time the high-pressure pounding away at blood vessels can cause heart attack, stroke and/or kidney failure, the type of end stage organ damage associated with hypertension, Dr. Pollock says.

In female rats at least, ETA receptors are less prone to reduce blood flow to the kidneys compared to males and actually increases sodium excretion without increasing blood pressure. Researchers found this by studying a rat missing the ETB receptor. When they gave the animals the protein endothelin to see if it could help them excrete salt without an ETB receptor, males did not respond but females experienced a significant improvement. When they took out the ovaries, female rats responded more like the males. Dr. Pollock says estrogen seems to drive the beneficial action of the ETA receptor. Additionally, researchers found stimulation of the ETB receptor increased urine output and sodium excretion in both sexes, suggesting that it was not a player in the differing responses between males and females.

"According to what we know, blocking the ETA receptor is a good thing and blocking the ETB receptor is a bad thing," Dr. Pollock says. Their findings indicate that actually may depend on whether you are a male or female rat and point to the need for human studies, he adds.

MCG researchers plan more laboratory studies to more specifically determine what different receptor subtypes are doing in the kidney's tubules and vasculature while colleagues at the University of Edinburgh in Scotland are beginning studies to look at how ETA receptor blockers impact sodium excretion in humans.

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Contact: Toni Baker tbaker@mcg.edu 706-721-4421 Medical College of Georgia Source:Eurekalert

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