Digestion and absorption of carbohydrates by the fetal lamb in utero

Intestinal digestive function was studied in 12 chronically catheterized third trimester fetal lambs by instilling glucose, fructose, lactose, maltose, and sucrose into their duodenums. Glucose was absorbed rapidly with the peak circulating glucose concentration reached within 1 hr. Fructose was absorbed well, but in contrast to glucose, blood fructose concentration did not peak; it continued to climb for 4 hr. Intraduodenal lactose administration resulted in a rapid rise in blood glucose with the maximum value reached in 1 hr. After receiving either glucose or lactose fetuses older than 130 days showed a faster rise in blood glucose, a greater total increase in glucose and a more rapid return to control levels than the younger fetuses. No change in blood glucose occurred with either maltose or sucrose administration. An increase in lactate concentration and a rise in fetal [H+] were noted after glucose and lactose administration, the only studies in which an increase in blood glucose concentration occurred.