Experimental aldosterone hypertension in the dog.

Sequential changes in arterial pressure, renal function, body fluid, and electrolyte balance, and several hemodynamic variables were examined during chronic intravenous infusion of aldosterone (14 micrograms/kg/day) in eight conscious dogs maintained on 250 mEq/day sodium and 140 mEq/day potassium intake. Arterial pressure gradually increased and stabilized at 132% +/- 3% (p less than 0.05) of the control value on the 16th day of aldosterone infusion, and cardiac output remained within the normal range. Coinciding with the rise in arterial pressure on the first 2 days of infusion was a marked retention of water and sodium and a rise in extracellular fluid volume and blood volume. Blood volume increased from a baseline value of 64.0 +/- 0.3 ml/kg to 70.7 +/- 1.9 ml/kg (p less than 0.05) on Day 4 and extracellular fluid volume increased from 318 +/- 5 ml/kg to 352 +/- 11 ml/kg (p less than 0.05) on Day 3 of infusion. Both blood volume and extracellular fluid volume remained elevated during infusion. Mean circulatory filling pressure increased from the baseline volume of 9.7 +/- 0.4 mm Hg to an average of 11.7 +/- 0.3 mm Hg (p less than 0.05) during the experimental period. The elevation of mean circulatory filling pressure suggested that this increase may be an essential component in the onset and maintenance of hypertension.