Effect of strain, sex and dietary riboflavin on pyridoxamine (pyridoxine) 5'-phosphate oxidase activity in rat tissues.

Weanling male rats of four strains--Buffalo, Long-Evans, Sprague-Dawley (SD) and Wistar--were fed a control or a riboflavin-deficient purified diet for 6 weeks. Both strain and diet had significant effects on pyridoxamine (pyridoxine) 5'-phosphate (PMP) oxidase activity in liver and kidney. No single strain had extreme PMP oxidase values or was consistently more responsive than the others to riboflavin deficiency. Weanling male and female SD rats were fed purified diets containing 2.5, 1.0, 0.5 or 0 mg of riboflavin/kg diet for 9 weeks. PMP oxidase values generally were lower in the females than in the males. In both sexes, increases in dietary riboflavin level were reflectd in increases in PMP oxidase activity in liver and kidney. These results confirm that PMP oxidase activity is a sensitive indicator of riboflavin status in the rat.