STUDIES ON THE ABSORPTION OF S-BENZOYLTHIAMINE O-MONOPHOSPHATE : (III) MECHANISM OF THE INTESTINAL ABSORPTION

Abstract

Mechanism of the intestinal absorption of S-benzoylthiamine O-monophosphate (BTMP) was investigated in dog. The small intestine was ligated to separate from the other part of intestine and the mesenteric vein was cannulated to collect the blood sample. After infusion of BTMP, the venous blood was analysed for total thiamine and the thiamine derivatives by means of chemical analysis and paper partitition chromatography. It was found that, 1) the absorption was detected in mesenteric venous blood immediately after the infusion and the blood thiamine concentration reached a maximum about 15 minutes after the infusion, 2) S-benzoylthiamine (SBT) was a main component of the total thiamine absorbed (ca. 60% at 15 minutes after the infusion) and the amount of free thiamine increased gradually with time, but no BTMP was detected, 3) a considerable part (30 to 40%) of the total thiamine absorbed was found in red cells already in mesenteric venous blood, 4) the total amount absorbed from the lumen in 1 hour was about 77% to the dose, 5) after 1 hour, BTMP was still detected in the lumen, while not in the intestinal wall, and 6) the absorption was significantly depressed in the presence of phosphatase inhibitors such as arsenate. From these results, it was concluded that BTMP is dephosphorylated at the intestinal mucosa and SBT is transported into the epithelial cells and transferred into mesenteric venous blood without significant change to thiamine. After infusion of BTMP to dog intestine, SBT was also detected (ca. 14% at 10 minutes after the infusion) in carotid blood, with thiamine as a main component, indicating that SBT is circulated in the body in peripheral blood.