The Relationship between Dietary Riboflavin Concentration and the Tissue Concentration of Riboflavin-Containing Coenzymes and Enzymes

1.The riboflavin intake necessary to maintain maximum tissue levels of riboflavin coenzymes varies with the organ and the particular coenzyme. In general, an intake of 30 μg per day was required to give maximum FAD and FMN concentrations in all tissues.2.The FAD and the FMN + free riboflavin concentrations in brain were almost independent of the amount of riboflavin in the diet. However, in kidney and liver, coenzyme concentrations were almost doubled when the intake was increased from no added riboflavin to 30 μg per day. In the heart muscle of riboflavin-deficient animals the FAD concentration and the FMN concentration were about the same whereas in kidney and liver tissues FMN concentration was less than the FAD content.3.The liver enzymatic activity depended on the riboflavin intake in the same manner as the coenzyme concentration. Both D-amino acid oxidase and xanthine oxidase activity increase with increased intake of riboflavin. Xanthine oxidase activity reached a maximum with an intake of about 30 μg of riboflavin per rat per day. D-Amino acid oxidase activity, on the other hand, increased up to an intake of over 60 μg riboflavin per rat per day.