ABSORPTION-ENHANCING EFFECTS OF SODIUM CAPRATE AND PALMITOYL CARNITINE IN RAT AND HUMAN COLONS

We examined the enhancing action of sodium caprate and palmitoylcarnit ine on the permeability of fluorescein isothiocyanate dextran 4000 as a paracellular permeant compound in isolated rat and human colon sampl es using the Ussing-type chamber method. In the absence of an enhancer , the permeation clearance of fluorescein isothiocyanate dextran 4000 was not significantly different in the rat and human colons, bat the e lectric membrane resistance was smaller in the rat colon than in the h uman colon. Sodium caprate and palmitoylcarnitine increased permeation clearance and decreased electric membrane resistance in both types of colonic membrane, showing that the rat colon can be used as a model o f the human colon for studies of enhancer effects. A calmodulin antago nist significantly inhibited the action of sodium caprate in both colo nic membranes. However, it tended to promote the effects of palmitoylc arnitine on permeation clearance and electric membrane resistance. The se results suggest that sodium caprate induces the contraction of the perijunctional actomyosin ring to widen the tight junction and that th e mechanism of palmitoylcarnitine is different from that of sodium cap rate in the human colon, as reported previously for Caco-2 cell monola yers.