In vivo D-glucose absorption in the developing rat small intestine.

Solutions containing D-glucose (1--20 mg/ml) were perfused in situ through the jejunum + ileum of anesthetized rats 7-8 and 14-15 (suckling), 21-23 (weanling), 35-36, and 70-73 days old. The amounts of glucose absorbed, expressed as percentage of load perfused (normalized for intestinal weight, milligrams per hour per gram wet weight), were greater in the weanling than in the suckling pups. Rate of glucose absorption increased with increase in glucose concentration in the perfused solutions and reached a plateau when concentration exceeded 3 mg/ml in the suckling and 10 mg/ml in the weanling rats. Based on intestinal weight, absorption rates (milligrams per hour per gram wet weight) from solutions containing 10 mg/ml glucose were 2 times greater in the 21-23 than in the 7-8-day-old pups (64 versus 30; P less than 0.01). Glucose absorption rates (milligrams per hour per gram wet weight of the perfused intestine) from the 20 mg/ml solution were similar in the 21-23 (64), 35-36 (60), and 70-73 (58)-day-old rats. The above results suggested that under the experimental conditions in rats the ability of the small intestine to absorp glucose per unit weight about doubles at the time of weaning as compared with the suckling period with no further enhancement thereafter.