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Dietary Regulation of Liver Glucose-6-Phosphate Dehydrogenase in the Rat: Starvation and Dietary Carbohydrate Induction¹

Biochemistry Section, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, and Department of Biochemistry and Molecular Biology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104

The previously reported dietary carbohydrate dependence of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and pyruvate kinase of rat liver has been further explored in rat liver cytoplasm under various conditions of starvation and refeeding. Similar but smaller influences of dietary carbohydrate were found on adrenal and on liver mitochondrial enzyme levels. In liver cytoplasm, glycogen accumulation appeared to be a precursor of the carbohydrate-dependent enzyme increases and, if so, could explain the increase in these enzymes following high dietary protein as well as carbohydrate. Orotate incorporation into liver nuclear RNA was seen after challenge of fasted rats with the high sucrose diet but not after challenge with the high fat diet. Actinomycin D and cycloheximide blocking of enzyme synthesis at zero time and cycloheximide but not actinomycin D blocking of enzyme increase several hours after sucrose indicates transcription level induction of synthesis following high sucrose diet feeding. The data seem consistent with regulation of these enzymes by the tissue levels of their specific substrates. The enzyme increases appear to involve fresh messenger RNA synthesis.

KEY WORDS: • G6PD • 6PGD • PK • sucrose • starvation-refeeding • actinomycin D • cycloheximide • induction • rat

¹ Supported in part by USPHS-GRS RR05538-10 and by NIH grant HE-12138.

² Present address: Federation of American Societies for Experimental Biology, Life Sciences Research Office, 9650 Rockville Pike, Bethesda, Md. 20014.

³ Present address: Department of Animal Nutrition and Agricultural Biochemistry. Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel.

Manuscript received 18 May 1972.