Concentration gradients of lactate, hydrogen and some other ions across the intestine in vitro

Abstract

When glucose-containing saline was circulated through rat intestine according to the method of Fisher and Parsons (Jour. Physiol. 119, p. 219, 1953) the concn. of lactate rose on the serosal side up to 9 times that on the mucosal side within 1 hr. The bicarbonate concn. decreased to about half the original value on the mucosal side while that on the serosal side remained practically constant. Thus glucose is converted into lactic acid, the lactate appearing mainly on the serosal side, the hydrogen ion appearing on the mucosal side. This was confirmed in expts. with sacs of everted intestine of the rat. Concn. gradients of lactate of 6 to 20 were observed. The concn. of bicarbonate decreased on the mucosal side while that on the serosal side remained constant or increased. Anaerobically the bicarbonate concn. on both sides of the sacs of rat intestine decreased, the decrease being equivalent to the increase in lactate concn. on the 2 sides. The lactate gradient did not appear under anaerobic conditions. Possible mechanisms for the lactate gradients are discussed. It is suggested that conversion of glucose into lactate may play a role in absorption of glucose in vivo. Sacs of everted ileum from the hamster can transfer bicarbonate from serosal to mucosal sides against a concn. gradient.