AUGUSTA, Ga.—Researchers may have discovered why premenopausal women have an edge in keeping a healthier balance between the amount of salt they eat and excrete.
A study at the Vascular Biology Center at the Medical College of Georgia and published in the February issue of Hypertension, said the reason appears to be related to female hormones and a newfound role of a cell receptor previously thought to be only harmful.
David Pollock, PhD, and colleagues said the finding points to the need for gender studies on how endothelin A, or ETA, receptors work in the blood vessels and tubules of the kidney. They also may help explain the swelling that occurs in some patients taking powerful new ETA antagonists, which are in use for pulmonary hypertension and under study for conditions such as diabetic nephropathy and uncontrolled hypertension. These antagonists block the action of ETA receptors which are believed to raise blood pressure and help reshape blood vessels into thick, rigid pipes.
ETA receptors have been considered the evil sibling of endothelin B, or ETB, receptors, which are believed to stimulate nitric oxide production, blood vessel relaxation and salt excretion. "Normally the ETB receptor system is a decision maker about how much sodium to keep and how much to excrete," Pollock said. "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," he said.
The body gets the sodium it needs from food and a healthy kidney should be able to eliminate excess from a high-salt diet so there is always a balance between 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, Pollock said.
