Salt Retention Hormone a Greater Factor In African American High Blood Pressure

Main Category: Hypertension
Article Date: 02 Feb 2005 - 19:00 PDT

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Hypertension, or high blood pressure, is 50 percent more prevalent in African Americans than in Caucasians, and salt retention may be a potent contributor to this high rate among African Americans. Aldosterone is an adrenal hormone that promotes salt-retention by the kidney. A new study by teams at the Medical College of Wisconsin and the University of Montreal, Canada suggests a significant link between higher levels of this hormone and high blood pressure in African Americans.

The teams evaluated aldosterone levels in relation to blood pressure in two distinct genetic populations: Milwaukee-area African Americans, and a group of geographically and genetically isolated French Canadians. Participants underwent physical assessments, medical histories and 24-hour in-patient monitoring of blood pressure and blood chemistry, including plasma aldosterone, while supine and standing.

Over 1,000 members of Milwaukee's African American community have contributed to this ongoing research at Froedtert Hospital, and more volunteers are needed.

The study was led by Theodore A. Kotchen, M.D., associate dean for clinical research and professor of medicine at the Medical College, and Pavel Hamet, M.D., Ph.D., at the University of Montreal. Their abstract appears in the October 2004 issue of Hypertension, where the full manuscript has been accepted for publication soon.

The researchers reported that blood levels of aldosterone are higher in African Americans with high blood pressure than in Caucasians, and that there is a highly significant correlation between blood levels of aldosterone and blood pressure in African Americans. In an earlier study, they also found that elevated aldosterone is directly related to over-development of the left ventricle of the heart in African Americans with high blood pressure.

These observations may point the way to drug therapies that would be particularly beneficial for African Americans with high blood pressure, according to Dr. Kotchen. "Specifically, we could predict that drugs that block the salt retaining effect of aldosterone in the kidney would be particularly effective agents to lower blood pressure in hypertensive African Americans," he says.

Ongoing, parallel research in experimental models of hypertension by Allen W. Cowley Jr., Ph.D., chairman and professor of physiology at the Medical College, may also help identify which patients with high blood pressure would benefit most from these new therapies. Dr. Cowley, director of the National Specialized Center of Research on the Molecular Genetics of Hypertension, is working to translate the genetic codes of salt-sensitive rats developed in his laboratory to the human genome.

The human studies are supported by grants from the National Institutes of Health (NIH), and conducted by Medical College researchers in the NIH funded General Clinical Research Center at Froedtert Hospital in Milwaukee, and by University of Montreal Preventive and Community Genomic Medicine Center researchers at Chicoutimi Hospital in the Saguenay-Lac St. Jean region of Canada.

African Americans may be eligible to participate in this research if they have high blood pressure and are ages 18 to 55, or if they have normal blood pressure and are ages 30 to 55. They cannot have diabetes, be pregnant or morbidly obese.

Medical College of Wisconsin
8701 Watertown Plank Rd.
Milwaukee, WI 53226
Phone 414-456-4700
Fax 414-456-6550
http://www.mcw.edu

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