Intestinal exsorption of oleic acid: influence of aging, bile, pH and ethanol.

The transfer of oleic acid from the circulation into the intestinal lumen perfusate (exsorption) was investigated in vivo in male Sprague-Dawley rats. Following intravenous infusion of oleic acid, its appearance in the intestinal perfusate was assessed over a 3-hour period. The relationship between exsorption rate and the amount of infused oleic acid delineated a linear plot. Oleic acid exsorption rate increased as the taurocholate concentration was raised to 10 mM in the intestinal perfusate. In contrast, oleic acid exsorption rate decreased following decrease in the intestinal perfusate pH, or increase in the intestinal perfusate's concentrations of oleic, butyric and octanoic acids or following the additions of increasing concentrations of ethanol to the intestinal perfusate. Increase in the age of the animals from 3 to 21 months resulted in a decrease of oleic acid exsorption. These data indicate that exsorption of oleic acid into the intestinal perfusate is not simply a process of "leakiness" of the intestinal epithelium. Rather, exsorption of this fatty acid is modified by factors that change the characteristics of the perfusate or modify the characteristics of the intestinal epithelium or the unstirred water layer at the luminal surface of the small intestine.