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Studies of the Effect of Dietary Cholesterol on Hepatic Protein Synthesis, Reduced Glutathione Levels and Serine Dehydratase Activity in the Rat¹

Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824

A basal diet or a basal diet plus 1% of cholesterol and 0.33% cholic acid was fed to rats for varying lengths of time and (1) the activities of liver phosphoenolpyruvate-carboxykinase (PEP-CK), tyrosine transaminase (TT), and serine dehydratase (SD); (2) the rate of total hepatic protein synthesis; and (3) the concentration of hepatic reduced glutathione (GSH) were quantitated. The specific activity of PEP-CK was significantly depressed by cholesterol plus cholic acid feeding, while the specific activity of TT was unchanged. No significant effect of dietary cholesterol plus cholic acid was found on the total liver activities. In contrast, SD specific activity was increased 3-fold. The rate of (U-¹⁴C)-L-leucine incorporation into total TCA precipitable protein following ingestion of cholesterol plus cholic acid was significantly reduced when the data were expressed as dpm (U-¹⁴C)-L-leucine /mg protein. After correcting this expression for specific radioactivity of the liver tissue free leucine pool, no significant effect of dietary cholesterol plus cholic acid on hepatic protein synthesis existed. In fact, the amount of ¹⁴C-leucine incorporated into protein on a total liver basis was 50% greater for the cholesterol group. On a per gram of liver basis, the concentration of GSH in the liver of rats fed a cholesterol plus cholic acid diet was significantly decreased. Considering the liver enlargement in rats fed cholesterol plus cholic acid, total organ GSH was found to be significantly greater than for rats fed a basal diet.

KEY WORDS: • cholesterol • protein synthesis • serine dehydratase

¹ Supported in part by Public Health Service Grant No. HL 14677 from the Heart and Lung Institute. Michigan Agricultural Experiment Station Journal Article No. 7221. Supported in part by NIH GM 01818.

² Present address: ACT—School of Public Health, Nutrition Program, University of Michigan, Ann Arbor, Michigan 48104.

Manuscript received 21 July 1975.