抄録
The tissue accumulation method was ascertained to be a more suitable method for studying the intestinal absorption mechanism in vitro than the everted sac method. By means of the tissue accumulation method, the absorption mechanism of thiamine from the rat small intestine was investigated. The ratio of intracellular to extracellular concentration was found to exceed unity with respect to free thiamine, indicating that thiamine is transported against a concentration gradient. Then, thiamine uptake by the intestinal segments was saturable and dependent on the incubation temperature. The transport required metabolic energy and was inhibited by pyrithiamine and chloroethylthiamine competitively. These evidences indicate that thiamine is absorbed from the rat small intestine by active transport.
Chloroethylthiamine, which has no inhibitory effect on thiamine pyro-phosphokinase, inhibited thiamine transport. Moreover, thiamine pyrophosphokinase was scarecely detected in microvillous membrane. The longitudinal distribution of thiamine pyrophosphokinase activity along the digestive tract did not coincide with that of the activity of thiamine uptake. These results indicate that there is a carrier system for thiamine transport which is not dependent upon the phosphorylation process in the rat small intestine.
