Vitamin Absorption Studies

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Abstract
Male weanling rats were depleted of riboflavin and then given the vitamin by stomach tube or subcutaneous injection at one-, two- or 4-day intervals. The animals receiving riboflavin orally showed a stepwise reduction in growth rate as the time interval between doses increased. Riboflavin given subcutaneously every other day was utilized as efficiently for growth as that given daily, but administration at 4-day intervals resulted in reduced weight gains. Metabolic studies with riboflavin-C14 showed that large oral doses were inefficiently absorbed, whereas large subcutaneous doses were inefficiently stored in the carcass and were for the most part excreted in the urine. Liver riboflavin stores were not influenced by the mode or frequency of administration of the vitamin. In similar studies with thiamine, animals given the vitamin daily or every other day, by oral or subcutaneous administration, grew at comparable rates. Although rats given thiamine subcutaneously every 4 days grew at similar rates to those receiving it daily, oral administration at 4-day intervals significantly reduced weight gains.