THE EFFECT OF ALDOSTERONE ON SODIUM AND POTASSIUM DISTRIBUTION IN MAN

Abstract

SUMMARY Total exchangeable sodium, potassium and bromide space were measured by a triple isotope technique, and antipyrine space, body weight, plasma electrolyte concentrations and urine electrolyte excretion were determined before and after intramuscular injection of 0·5 mg. aldosterone 6-hourly for 6–8 days in nine convalescent men. After the treatment with aldosterone there were mean increases in body weight of 2·5 kg., 2·5 1. in total body water, and of 3·0 1. in extracellular fluid volume; a slight decrease in intracellular fluid volume was not significant. The mean total exchangeable sodium increased by 463 m-equiv. and the mean cumulative urinary excretion of sodium decreased by 444 m-equiv. The sodium was retained in the extracellular fluid without significant change in exchangeable intracellular sodium. Mean total exchangeable potassium was reduced by 207 m-equiv. while mean cumulative urinary potassium excretion increased by 88 m-equiv. The potassium loss was entirely intracellular. The main source of error arose from isotope counting. The coefficient of variation of the sample count minus the background exceeded ±3% in 18 out of 150 samples: these results were discarded. Sixteen of the inaccurate counts were due to low concentrations of sodium or potassium in the specimens.