Developmental changes of sugar transport in the ovine small intestine.

Intestinal monosaccharide transport was studied in young lambs (age: up to 1 week) and in older lambs (age: 2.5-4 months) with well developed forestomach system employing everted sacs of small intestine. Both glucose and galactose were transported against a high concentration gradient from the mucosal to the serosal side of the intestinal wall in young lambs. In the older lambs glucose was transported only against a small concentration gradient, when intestinal glucose metabolism was diminished by reducing the pH of the incubation medium from 7 to 5. Galactose and alpha-methyl-glucoside, which are not markedly metabolized by the intestine, were transported against a small but similar concentration gradient at both pH values in these animals. In young lambs, however, at pH 5 intestinal galactose transport was lower than at pH 7. These results indicate that active intestinal monosaccharide transport becomes rudimentary in the maturing sheep.