Role of Mineralocorticolds In the Natriuresis of Water Immersion in Man

The role of aldosterone suppression in mediating the natriuresis of water immersion was assessed in six normal male subjects. All subjects were studied on four occasions while they were in balance on a diet containing 150 mEq of sodium and 100 mEq of potassium daily: during a control period, following deoxycorticosterone acetate (DOCA) treatment for 24 hours (Cont+ DOCA), during water immersion to the neck (immer-sion), and during water immersion following DOCA treatment (Imm + DOCA). Immer-sion resulted in highly significant increases in the rates of sodium and potassium excretion compared with control beginning in the first hour. Although treatment with DOCA de-creased the natriuresis of immersion (P<0.01) , the rate of sodium excretion was still three- to fourfold greater during Imm + DOCA than it was during the comparable Cont + DOCA periods (P < 0.01). Cessation of water immersion resulted in a marked decrease in urine flow and free water clearance occurring within the initial 30 minutes of recovery (P < 0.005). Although the rate of sodium excretion also decreased following cessation of immersion, it continued to exceed both preimmersion values (P<0.01