ABSORPTION AND SECRETION IN THE COLON

New studies continue to define how colonic absorption and secretion ar e regulated by intracellular pH, peptides, inflammatory mediators, lax atives, and antidiarrheal agents. Additional work has addressed the in fluence of aldosterone on electrogenic sodium absorption and has shown the importance of nutritional status in the action of vitamin A on th yroid hormone modulation of aldosterone action. There is further evide nce implicating platelet-activating factor as a mediator of intestinal secretion in inflammatory bowel disease and in the mechanism of actio n of anthraquinone laxatives. The activity of peptide YY, pituitary ad enylate cyclase-activating polypeptide, endothelin 1, and guanylin sug gest that these peptides may have physiologic or pathophysiologic effe cts on colonic transport. Studies on methods to enhance the absorption of peptides through the colonic mucosa indicate that it may be possib le to improve systemic bioavailability of peptides via this route of a dministration.