Kinetics of hexose uptake by the small and large intestine of the chicken

The kinetic parameters of hexose uptake by the small and large intestine of the chicken have been determined in vitro. Rates of initial influx of alpha-methyl-D-glucoside and L-glucose were measured in everted sleeves of the duodenum, jejunum, ileum, proximal cecum, and rectum. Results show the following. 1) Maximal transport capacity values for alpha-methyl-D-glucoside show that the jejunum is the segment that is best suited for Naf-mediated uptake. 2) The calculated apparent Michaelis constant values were (in mmol/l) 11.6 for duodenum, 7.8 for jejunum, 3.5 for ileum, 2.4 for proximal cecum, and 7.1 for rectum. This suggests that, with the exception of the rectum, the affinity of the carrier for alpha-methyl-D-glucoside progressively increases in the distal direction. 3) Diffusion constant Values indicate that influx of hexoses by a passive mechanism in the duodenum and proximal cecum is significantly higher than in the other segments. 4) The sum of passive and mediated mechanisms confers to the duodenum and jejunum a high capacity to absorb hexoses. The ileum, proximal cecum, and rectum have a quantitatively minor role, albeit significant, in completing the absorptive function.