THE ABSORPTION OF SOME B-GROUP VITAMINS BY SURVIVING RAT INTESTINE PREPARATIONS

¹ Medical Research Council, Cell Metabolism Research Unit, Department of Biochemistry, University of Oxford; Plant protection Ltd., Imperial Chemicle Industries Ltd., Jealott's Hill Research Station, Bracknell, Berkshire
² Medical Research Council, Cell Metabolism Research Unit, Department of Biochemistry, University of Oxford

Everted sacs of rat small intestine transferred mixtures of B-group vitamins (nicotinic acid, pantothenic acid, biotin, thiamine, folic acid and vitamin B₁₂) from mucosal to serosal side and in the reverse direction at approximately equal rates. No marked concentration changes occurred when equal concentrations of vitamins were placed on both sides. There was no evidence of concentration of any of the vitamins against a concentration gradient. The movement of vitamins was not markedly affected by the addition of substrates (glucose, -oxoglutarate, acetate and pyruvate) or inhibitors (azide, cyanide, phlorrhizin). The magnitude of water movements bore no simple relationship to vitamin movements. Substantially the same results were found with segments of rat intestine through which the vitamins were circulated and with sacs of hamster intestine. It is concluded that the absorption of vitamins from the intestine is by passive diffusion and these rates are sufficient to account for the daily uptake of vitamin from the diet.

Note:

We wish to acknowledge the help and advice given to us by Professor Sir Hans Krebs. Thanks are also due to Miss Susan Graham for technical help. This work was aided by a grant to the Biochemistry Department from the Rockefeller Foundation. J.B.T. is indebted to the Medical Research Council for a training scholarship and to the Fellows of Queen's College, Oxford, for a Senior Hastings Scholarship.