Decreased Hepatic Gluconeogenesis in Vitamin A-Deficient Rats

Abstract

Abstract

Studies were carried out to investigate the effects of vitamin A deficiency (hypovitaminosis A) on the chemical constituents and gluconeogenic activity of rat liver. Hypovitaminosis A was found not to alter the glycogen, protein, DNA, or RNA content, but to decrease significantly the level of citrate in liver. Free amino acid levels in blood and liver of vitamin A-deficient rats were markedly higher in comparison to pair fed controls. An inhibition of hepatic gluconeogenesis in vitamin A deficiency was indicated by the decreased incorporation of ¹⁴C-labeled alanine and bicarbonate into glucose and glycogen by liver slices. Vitamin A deficiency caused a significant decrease in the activities of alanine aminotransferase, ornithine aminotransferase, glucose 6-phosphatase and fructose 1,6-bisphosphatase. Activities of aspartate aminotransferase and tryptophan pyrrolase were found to be unaltered in vitamin A-deficient livers. It is suggested that the inhibition of hepatic gluconeogenesis observed in hypovitaminosis A may be due in part to an impairment in the substrate flux into the gluconeogenic pathway.