WATER AND SALT ABSORPTION IN THE HUMAN COLON*†

Abstract

A method using constant perfusion of the colon via an orally introduced tube was used to study unidirectional water fluxes as well as absorption of water and electrolytes in the colon of healthy intact men. The perfusion fluid was 0.85% sodium chloride solution containing tritiated water and a nonabsorbable reference substance, polyethelene glycol. The test solution was sampled via a rectal tube in all cases and in 3 cases in the mid-colonic area as well. A total of 36 test periods of 20 minutes each were carried out in 7 subjects. Under the conditions of our experiments, the entire colon absorbed on the average 1.7 ml of water, 0.28 mEq of sodium, and 0.39 mEq of chloride per minute, and at the same time secreted 0.031 mEq of potassium and 0.18 mEq of bicarbonate per minute. The mean water flux out of the lumen was 7.8 ml per minute and flux into the lumen was 6.0 ml per minute. Larger unidirectional water fluxes were observed in the right than in the left colon.