FLUID AND SOLUTE TRANSPORT ACROSS RAT COLONIC MUCOSA

Abstract

A method is described of preparing everted sacs of rat colonic mucosa free of the smooth muscle layers. Fluid movement across the wall of the sacs may be maintained for periods of up to 4 hr. in vitro under aerobic conditions in the presence of a substrate. Glucose, mannose, acetate, butyrate and to a lesser extent, pyruvate, are effective substrates. Although taken up from the mucosal fluid, glucose is most effective as a substrate for fluid movement when present in the transmucosal fluid. In the presence of glucose, the rate of lactate formation is low under aerobic conditions in vitro , but increases some eight‐fold under anaerobic conditions. With glucose present, lactate appears at a higher concentration in the transmucosal fluid than in the mucosal fluid. The colon can transport water from mucosal fluid into the transmucosal fluid against an osmotic gradient; reasons are given for supposing that this fluid movement is secondary to the functioning of an active solute transport mechanism. Glucose, galactose and 3‐0‐methylglucose are not subjected to active transport (translocation) across the colonic mucosal layers against a concentration gradient.