Precocious enhancement of intestinal fructose uptake by diet in adrenalectomized rat pups.

Intestinal fructose transport typically increases 3-fold after completion of weaning (> 28 d of age) in rats allowed to wean normally. Precocious enhancement of fructose transport has been demonstrated in rats fed high fructose diets during early weaning. To determine the role of corticosterone in the enhancement of fructose uptake by diet, we fed 17-d-old rat pups, previously adrenalectomized or sham-operated at 10 d of age, high (65%) fructose or fructose-free diets for 3 d. Corticosterone levels in 20-d-old sham-operated and unoperated controls were 2.2-3.3-fold higher than those in adrenalectomized littermates and in unoperated 10-d-old pups. Fructose uptake per mg and per cm were each 2.0-2.5-fold higher in adrenalectomized and sham-operated pups fed high fructose diets compared with those in adrenalectomized and sham-operated littermates fed fructose-free diets or to those in unoperated littermates allowed to wean normally with the dam. An increase in levels of GLUT5 mRNA in pups fed high fructose diets paralleled the increase in rates of fructose uptake. Intestinal glucose uptake was independent of corticosterone levels and of diet. Thus, the corticosterone surge is not necessary for the precocious enhancement of intestinal fructose transport and of GLUT5 mRNA expression by dietary fructose during weaning.