EVALUATION OF RACIAL DIFFERENCES IN ALDOSTERONE AND SODIUM REGULATION

Virginia Commonwealth University, Richmond VA

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Abstract

An attempt to determine the racial differences in Aldosterone regulation as a contributing factor to salt sensitivity in hypertensive patients. High blood pressure is a major concern in the United States. It has been estimated that 43 million people have high blood pressure. An increased prevalence of hypertension in the black population was first noted 60 years ago. Since then, studies have attempted to study the mechanism for the increased risk. To date, the differences remain uncertain. Aldosterone is a steroid hormone produced in the adrenal cortex in the area of the kidneys. The major effects of aldosterone are to promote salt retention and potassium loss by the kidneys. It can have a similar effect on other tissues including the colon, sweat glands, and salivary glands. Studies have shown that black hypertensives and blacks with normal blood pressure excreted the sodium load more slowly and less completely than white subjects. Black patients also had a greater increase in blood pressure in response to salt loading. The aims of the study are: 1. To categorize black and white hypertension patients as salt sensitive using a saline loading/lasix diuresis protocol (increased urine output). 2. To analyze aldosterone regulation by saline loading in black and white patients. 3. To analyze day/night rhymicity of aldosterone and electrolyte excretion in black and white hypertensive patients at baseline, following saline loading, and following lasix diuresis. 4. To evaluate the role of dopamine using metoclopromide, a dopamine antagonist. 6. To evaluate the sensitivity of aldosterone secretion to oral potassium supplementation following lasix diuresis. The study will last for three weeks during which blood pressure medication will be stopped. Blood pressure will be monitored weekly. The first visit to the Clinical Research Center will take place one week after medication has been discontinued. Metoclopromide will be given intravenously and blood samples will be taken. The following week, a 24 hour urine will be collected and a special diet of controlled sodium and potassium will be given. The next day, there will be periodic urine collections from 8a.m. to 10 p.m. while the patient remains upright. On the third day, blood and urine will be taken and saline and furosemide, a medication that will increase the urine output, will be administered. On the fifth day, potassium chloride will be given and blood and urine samples will be taken. After the study, blood pressure medication will be continued.