An in vitro study of choline uptake by intestine from neonatal and adult rats.

We studied choline uptake by slices of adult and 10-day-old rat intestine which were exposed on their mucosal surface to radiolabeled choline. Both neonatal and adult intestine transported choline. Choline uptake was observed in duodenum, jejunum, ileum, and colon of the adult rat. In the small intestine, choline uptake consisted of two components: a saturable and a nonsaturable process. The kinetic variables for saturable transport (Km, Vmax) were not significantly different in adult and neonatal small intestine. Some of the transported choline was converted to phosphatidylcholine, glycerophosphocholine, phosphocholine, and betaine. However, most of the transported choline (79-85%) was not metabolized within the intestinal slice during a 15-min period. We conclude that the capacity for choline transport in the rat small intestine is present early in neonatal life. The characteristics of this transport mechanism for choline are similar in the neonate and in the adult small intestine. Neonates should therefore be able to absorb the large amounts of unesterified choline that are present in milk.