The Absorption of Some B‐group Vitamins by Surviving Rat Intestine Preparations

Everted sacs of rat small intestine transferred mixtures of B‐group vitamins (nicotinic acid, pantothenic acid, biotin, thiamine, folic acid and vitamin B 12 ) 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, α‐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.