Choline transport by rat small intestine

Abstract

Choline uptake into the small intestine of the rat was investigated using an in vitro technique. Throughout the small intestine of the adultrat, Choline uptake occurs by two processes: (1) a carrier-mediated, saturable mechanism; and (2) a non-saturable process, dependent on external choline concentration. Non-mediated uptake is greater in the ileum than in other areas of the adult small intestine. In the ileum, the carrier-mediated component is an energy-requiring system (inhibited by cyanide and nitrogen) which.exhibits specificity for choline (inhibited by hemicholinium-3). The mechanism of choline uptake into the small intestine of the developing rat is similar to thatfound in the mature intestine: a carrier-mediated transport system and a non-mediated process dependent on choline concentration. The estimates for Km and Vmax of the mediated component in the developing small intestine are greater than estimates for the same parameters in the adult intestine. These differences in transport characteristics are not due to differences in the metabolism of choline by the small intestine at different ages. However, feeding per se may partially account for differences in the apparent kinetic constants determined.