EFFECTS OF FASTING AND GLUCAGON ON THE KINETICS OF ACTIVE HEXOSE ABSORPTION ACROSS THE RAT DISTAL ILEUM IN VIVO

¹ Department of Physiology, Royal Free Hospital School of Medicine, Rowland Hill Street, London NW3 2PF

The effects of starvation for 1, 2 or 3 d and the administration of glucagon to fed rats on the kinetics of active glucose and galactose absorption across the distal ileum have been determined in vivo. Fasting caused reductions in ‘apparent K_t’ for glucose and galactose transport together with a decrease in J_max for glucose but not galactose absorption. Treatment with glucagon produced decreases in K_t for the absorption of both hexoses and an increase in J_max for glucose absorption. The J_max for galactose uptake, however, was unaltered by glucagon administration. Villus size was unaltered by starvation of up to 3 d duration, but significantly decreased by glucagon treatment. The results suggest that chronically elevated plasma glucagon levels may be a factor in the change in kinetics of hexose absorption in the distal ileum evoked by fasting.