THE KINETICS OF SODIUM-DEPENDENT PHENYLALANINE INFLUX IN THE INTESTINE OF THE DOG - A COMPARISON BETWEEN ILEUM AND COLON

  • 1 January 1980
    • journal article
    • research article
    • Vol. 76  (6) , 637-645
Abstract
The kinetics of Na-dependent phenylalanine influx into samples of dog ileal and colonic mucosa in vitro were compared and contrasted. The data were evaluated by non-linear regression analysis, on the assumption that the total influx of the amino acid is made up of the sum of a single saturable and a diffusive component. In the 2 mucosae, the principal effect of changing the Na concentration in the incubation medium was to alter the Kt [transport constant] for phenylalanine influx. The results were compatible with a general non-compulsory model for the formation of a ternary complex, between the carrier, a phenylalanine molecule and a Na ion which can be formed from binary complex, i.e., species can combine 1st with the carrier. Within the context of this model, the Vmax for phenylalanine influx was apparently, substantially smaller in the colon than in the ileum. The constants governing the dissociation of the ternary complex into the binary complex were significantly smaller in the colon, while the dissociation constants of the binary complexes were similar in the 2 regions of the intestine.