Effects of Riboflavin Deficiency upon Concentrations of Riboflavin, Flavin Mononucleotide, and Flavin Adenine Dinucleotide in Novikoff Hepatoma in Rats1

The concentrations of riboflavin and of the two coenzymes derived from riboflavin, flavin mononucleotide and flavin adenine dinucleotide (FAD), were determined in Novikoff hepatoma grown i.p. and in host liver of normal and riboflavin-deficient male Holtzman rats. Riboflavin deficiency significantly prolonged the 50% survival time of tumor-bearing animals from 5.7 to 10.8 days. The growth of Novikoff hepatoma did not alter hepatic riboflavin, flavin mononucleotide or FAD concentrations in either normal or riboflavin-deficient rats. In tumor from riboflavin-deficient rats, the concentration of FAD was nearly identical to that in tumor from animals on a normal diet. By contrast, in tumor from deficient animals, the flavin mononucleotide concentration was significantly lower than that in tumor from control animals. The free riboflavin concentration was decreased even further and was undetectable in one-third of the tumors from riboflavin-deficient animals. The FAD pyrophosphorylase activity was increased in liver but not in tumor from riboflavin-deficient animals.