Abstract
The transport of ^3H-pyridoxal (^3H-PAL) across the intestinal wall was studied with the everted sacs of rat small intestine, mainly at an initial ^3H-PAL concentration of 0.3μM on the mucosal side. The serosal concentration of labelled compounds continuously increased, but did not reach the mucosal level during 4-hour incubation at 37℃, and the time course apparently subjected to first-order kinetics during the first 2 hours of incubation. Addition of 300μM 4-deoxypyridoxine or 10-fold increase of initial mucosal ^3H-PAL concentration did not significantly affect the time course of the ratio of serosal to mucosal concentration, but affected the extent of ^3H-PAL uptake by the tissue. The transport at 0℃ was much slower than that at 37℃ and apparently subjected to first order kinetics for 4 hours. Comparison of the rate constants with those of pyridoxine showed that PAL was transported faster than pyridoxine either at 37℃ or 0℃. Analysis of the serosal ^3H-compounds after 2-hour incubation with 0.3 or 3μM ^3H-PAL by column chromatography on Dowex 50W indicated that almost of them was ^3H-PAL.
