The absorption and secretion of water and electrolytes across the healthy and the diseased human colonic mucosa measured in vitro.

An ;in-vitro' technique is described for measuring quantitatively the absorption and secretion of water and electrolytes, the short circuiting current, and the simultaneous bidirectional flux rates of ions across the healthy and diseased colonic mucosa. The results show that the normal colon absorbs both sodium and water and secretes potassium. In both ulcerative colitis and Crohn's disease there is a reversal of sodium and water flux and potassium secretion is increased.A measure of the simultaneous bidirectional flux rates under conditions of zero potential has allowed us to use the Ussing equation to analyse some of the factors involved in sodium transport across the healthy and diseased mucosa.