Developmental maturation of D-glucose active transport system in rat intestine

Developmental changes in the D-glucose-active transport system were examined in jejunum of rats of different age groups (3, 5, 7, 11, 13, 17, 25 and 90 days old) using the intestinal sheet technique. Transport of D-glucose by the active system was determined by subtracting the passive component, as determined by uptake of L-3H-glucose from the total uptake. The transport rate of 0.1 and 1 mM D-glucose in 13- and 90-day-old rats was linear with time for 12 min of incubation, but decreased thereafter. Kinetic parameters of the active transport system of D-glucose were determined by examining the transport of D-glucose after 12 min of incubation as a function of concentration. Vmax of the active transport system was highest in 3-day-old rats and decreased with age reaching the adult value by day 7 after birth. Kt of the active transport system was the same in 3- 5- and 7-day-old rats, but increased progressively with age reaching the adult value by day 25 after birth. These data demonstrate that transport of D-glucose by the active system is highest during the early days of life, but decreases thereafter. It also suggests that this enhancement is most probably due to greater activity and/or number, and affinity of the transporting carriers of D-glucose.