Mechanism of Intestinal Absorption of Thiamin

Abstract

Our data show that injections of thyroxin do not increase the rate of intestinal absorption of thiamin chloride in rats as they do in the case of dextrose and other substances susceptible to phosphorylation. This observation would indicate that phosphorylation plays no dominant part in determining the rate of intestinal absorption of thiamin or that thyroxin has no stimulating effect on the rate of enzymic formation of the pyrophosphate ester linkage. The stimulating effect of thyroxin may be limited to the phosphorylating processes involving the mono-phosphoric acid ester, as in the transport of dextrose across the intestinal mucosa. The conclusion that phosphorylation plays no part in the intestinal absorption of thiamin is supported also by the work of Ochoa, who found that in vitro intestinal tissue, in contrast to liver tissue, possesses little ability to phosphorylate thiamin.