Effect of d-Aldosterone on Salt and Water Absorption from the Intact Human Colon*

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Abstract
Net NaCl, and water absorption from the human colon before and after intravenous administration of 1 mg of d-aldosterone was studied in 12 healthy, recumbent subjects on an unrestricted salt intake. A test solution containing 0. 85% NaCl was infused into the cecum at a constant rate of 10 ml/min. A non-absorbable reference substance, polyethylene glycol, in the concentration of 1% was added to the test solution in order to measure water absorption. The test solution that had traversed the entire colon was collected by a rectal tube. A significant increase in the Na absorption was observed 24 hr. after aldosterone administration. Similarly, net Cl and net water absorption was increased. Twenty-four hours after aldosterone administration, the mean net absorption of Na for the entire study group rose from 0. 41 mEq/min. to 0. 67 mEq/min.; Cl-rose from 0. 62 mEq/min. to 0. 79 mEq/min.; and water from 2. 24 ml/min. to 3. 77 ml/min. No significant increase in K secretion was observed. These studies suggest that the colon, like other Na transporting systems, is influenced by aldosterone. Unlike other biological systems, however, the aldosterone effect on the human colon was not noted within 3 hr. but was evident 24 hr. after administration.