Gluconeogenesis in meal-fed, vitamin B-6-deficient rats

Male weanling rats were meal-fed (2 hours daily) on a vitamin B-6-deficient diet for 8 weeks; the controls were pair-fed. Vitamin B-6 deficiency led to the expected decreases in the activities of hepatic alanine and aspartate aminotransferases but did not influence those of glutamate dehydrogenase (EC 1.4.1.2), pyruvate carboxylase (EC 6.6.1.1), phosphoenolpyruvate carboxykinase (EC 4.1.1.32) and pyruvate kinase (EC 2.7.1.40). The ability of the deficient rats to incorporate 14C from labeled alanine into blood glucose and expired CO2 was diminished, but pyruvate-U-14C was utilized normally. The deficiency did not influence gluconeogenesis from glutamate or 2-oxoglutarate. Furthermore, the gluconeogenic potential of renal cortex slices incubated with pyruvate or 2-oxoglutarate was unaltered by the deficiency. These data suggest that the impairment of gluconeogenesis from amino acids in vitamin B-6 deficiency may be the consequence of diminished transamination prior to oxidative deamination.