SPIRONOLACTONE ADMINISTRATION AND TRAINING-INDUCED HYPERVOLEMIA

The purpose of this study was to determine the contribution of aldosterone to plasma volume expansion accompanying short-term exercise training. Twelve healthy males (age = 26.5 +/- 5.8) cycled for 120 min on three consecutive days at a relative exercise intensity of 65% VO(2)max. Half of the subjects were treated with 25 mg of spironolactone taken four times daily to suppress the effects of aldosterone. Resting plasma volume increased significantly (501 +/- 83 ml, p < 0.05) from pretraining in control subjects, but not for drug-treated subjects (163 +/- 94 ml). Spironolactone attenuated gains in resting plasma volume, serum sodium content, and serum osmolal content by 67 %, 79 % and 66 %, respectively. Spironolactone-treated and non-treated subjects experienced similar increases in total serum protein content sufficient to increase the plasma volume by approximate to 290 ml. It was not determined why drug-treated subjects attained less of a plasma volume expansion than that expected by the increase in oncotic pressure. In conclusion, two-fifths of the plasma volume expansion induced by 3 d of endurance cycling could be attributed to aldosterone activity, and the remaining three-fifths could be explained by the expansion of intravascular protein mass. Other neurohormonal influences may have contributed to the overall plasma volume expansion but this experiment did not allow for their exclusion.