Role of glucocorticoids and aldosterone in maintenance of colonic cation transport

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Abstract
Adrenalectomized rats were maintained on physiologic replacement doses of aldosterone or dexamethasone for 24 h after adrenalectomy. Net cation movement and transmural potential difference [PD] were determined during in vivo perfusion of the colon. Adrenalectomy without replacement steroids resulted in marked reduction of Na and H2O absorption, K secretion and transmural PD. Aldosterone 10 .mu.g .cntdot. 100 g body wt-1 per 24 h significantly increased net K secretion above adrenalectomized levels but did not restore transport to control levels. Na and H2O absorption and transmural PD were not affected. Aldosterone 30 .mu.g .cntdot. 100 g body wt-1 per 24 h increased but did not restore net mvoement of Na or K to control levels. In contrast to aldosterone, physiologic amounts of dexamethasone, 10 .mu.g .cntdot. 100 g body wt-1 per 24 h, preserved normal electrolyte movement and electrical properties in adrenalectomized rats. In additional experiments the aldosterone antagonist spironolactone was administered for 3 days to rats with intact adrenal function. Net Na absorption fell only 22% below control with insignificant decreases in K secretion and transmural PD. Glucocorticoid hormones apparently exert regulatory control of basal colonic fluid and electrolyte function.