Intestinal transport of tryptophan and its derivatives

Abstract

The intestinal transport of l- and d-isomers of tryptophan and ten derivatives were studied in everted intestinal sacs of golden hamsters. It was found that l-tryptophan, 4-CH3-, 5-CH3-, and 6-CH3-dl-tryptophan, and N-chloroacetyl-l-tryptophan were transported against a concentration gradient and the d-isomer, 5-OH- and 5-benzyloxyl-dl-tryptophan, N-acetyl-l- and N-2,4-dinitrophenyl-dl-tryptophan, tryptamine and 5-OH-tryptamine were not transported. The rate of l-tryptophan transport was much greater than that of the methyl derivatives and N-chloroacetyl-derivative. The transport reached saturation at 3 mm concentration and was inhibited in presence of 6 mm of l-tyrosine or l-phenylalanine. Kinetic study showed that this inhibition was a competitive one. Studies with H3-dl-tryptophan have shown that the transport mechanism was mainly located in the mucosal, not the serosal side. Replacement of Na+ ion either by Li+, K+, or choline in either mucosal or both sides, inhibited the tryptophan transport. Replacement of chloride by sulfate did not show any inhibitory effect.