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Journal of Nutrition Vol. 107 No. 10 October 1977, pp. 1809-1815
Copyright © 1977 by American Society for Nutrition
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Early Effects of Hypervitaminosis A on Gluconeogenic Activity and Amino Acid Metabolizing Enzymes of Rat Liver1

K. N. Dileepan, Vishwa Nath Singh2 and C. K. Ramachandran

Department of Biochemistry, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi-110007 ( India)

In an earlier report from this laboratory, one of the early manifestations of hypervitaminosis A was shown to be a marked stimulation of hepatic gluconeogenesis. In the present study, effects of feeding 30,000 IU of retinyl palmitate to young rats (80–100 g), once daily, for 2 days on the incorporation of 14C-labeled precursors into glucose and glycogen by liver slices, levels of amino acids in blood and tissues, and activities of some important amino acid catabolizing enzymes in the liver were investigated. A stimulation of hepatic gluconeogenesis in hypervitaminosis A was indicated by the increased incorporation of 14C-labeled alanine and bicarbonate into glucose and glycogen by liver slices. Excessive intake of retinol caused a marked increase in the activities of hepatic alanine aminotransferase and ornithine aminotransferase and a decrease in that of tryptophan pyrrolase, without affecting those of tyrosine aminotransferase and serine dehydratase. The ratio of NADH:NAD in the livers of rats fed excess retinol was significantly increased. It is suggested that enhancement of gluconeogenesis in hypervitaminosis A is caused by a stimulation of gluconeogenic activity of the liver.

KEY WORDS: • Retinol • vitamin A • hypervitaminosis A • hepatic gluconeogenesis • amino acid metabolism • amino-transferases

1 This investigation was supported by a grant from Indian Council of Medical Research, New Delhi, India.

2 To whom the reprint request should be addressed.

Manuscript received 15 March 1977.




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