Effect of Methionine and Riboflavin on Free Amino Acids, Riboflavin and Lipids in Selected Rat Tissues

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Abstract
The effect of riboflavin and methionine supplementation of a riboflavin-deficient ration which contained 18% of casein, on the concentration of amino acids in plasma and riboflavin-containing coenzymes, cholesterol and total lipids in liver of rats was studied. The addition of 0.2% of l-methionine to a riboflavin-deficient basal ration which contained 18% of casein decreased the concentration of plasma valine in young rats fed 10 µg of riboflavin. A marked increase in plasma methionine was observed in animals fed 2.0% of methionine. A comparison of data for animals fed 2.0% of methionine and the basal ration showed an increase in plasma lysine for animals fed 10 µg of riboflavin. Increasing the riboflavin intake from 10 to 100 µg increased plasma methionine in animals fed 2.0% of methionine. The higher level of riboflavin resulted in increased plasma valine in animals fed the basal or 0.2% of methionine. Supplementation of the basal ration with 0.2% of l-methionine increased the growth rate of animals fed 100 µg of riboflavin above that of corresponding animals fed the basal ration but had no effect on animals fed 10 µg of the vitamin. The addition of 2.0% of l-methionine to the basal ration markedly decreased the growth rate of the animals fed either amount of riboflavin. Increased methionine intake increased the total riboflavin retention in liver of animals fed 100 µg of riboflavin. The concentration of liver cholesterol decreased with increased riboflavin and decreased with increased methionine with one exception in animals fed 10 µg of the vitamin. Supplemental methionine or riboflavin had little effect on total lipids in liver.