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The riboflavin economy of the rat


, : The riboflavin economy of the rat. Journal of Nutrition 64(2): 185-202

The concentration of riboflavin in the liver and in the rest of the carcass has been measured for weanling rats maintained for three to 5 weeks with zero to 160 [mu]g of riboflavin per day. With no dietary riboflavin tissue concentrations fell to a little less than half their initial value by the end of three weeks and then remained stationary. Maximum riboflavin concentrations were obtained with intakes of about 40 [mu]g per day. Maximum growth occurred with tissue riboflavin concentrations that were about 75% of the maximum levels attainable. Male rats grew more rapidly than females even with suboptimal tissue concentrations; hence with a given suboptimal intake of riboflavin, male tissues were lower in riboflavin than were female tissues. Destruction of riboflavin by the rat varied from as little as 0.04 [mu]g per gram per day in severe deficiency to more than 6 ug per gram per day when a large excess of riboflavin was administered. In addition to any riboflavin deposited in the tissues, approximately 0.2 [mu]g of riboflavin per gram per day was needed to balance destruction with tissue levels which permit maximum growth. No increase in riboflavin destruction by riboflavin deficient rats was observed when metabolism was increased by means of thyroxin or by a cold environment. Nor did changing the metabolic mixture to emphasize carbohydrate, protein or fat influence riboflavin destruction. Hence it is concluded that there is little or no direct destruction of riboflavin associated with its use.

US$29.90

PMID: 13526003


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