KINETICS OF HEXOSE UPTAKE BY THE SMALL AND LARGE-INTESTINE OF THE CHICKEN

The kinetic parameters of hexose uptake by the small and large intesti ne of the chicken have been determined in vitro. Rates of initial infl ux of alpha-methyl-D-glucoside and L-glucose were measured in everted sleeves of the duodenum, jejunum, ileum, proximal cecum, and rectum. R esults show the following. 1) Maximal transport capacity values for al pha-methyl-D-glucoside show that the jejunum is the segment that is be st suited for Naf-mediated uptake. 2) The calculated apparent Michaeli s 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 sugge sts that, with the exception of the rectum, the affinity of the carrie r for alpha-methyl-D-glucoside progressively increases in the distal d irection. 3) Diffusion constant Values indicate that influx of hexoses by a passive mechanism in the duodenum and proximal cecum is signific antly higher than in the other segments. 4) The sum of passive and med iated mechanisms confers to the duodenum and jejunum a high capacity t o absorb hexoses. The ileum, proximal cecum, and rectum have a quantit atively minor role, albeit significant, in completing the absorptive f unction.