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Ribonucleic Acid Metabolism in Rat Liver During Long-Term Adaptation to Malnutrition^1,2,3,

S. Jaime Rozovski^*, Charles G. Lewis and Mabel Cheng^*

^* Institute of Human Nutrition and School of Public Health, Faculty of Medicine, Columbia University, New York, NY 10032 Department of Food and Nutrition, College of Health, University of Utah, Salt Lake City, UT 84112

Ornithine decarboxylase (ODC) and nucleolar DNA-dependent RNA polymerase (RNA polymerase I) activities increased in the liver of young adult male rats fed a 6% casein diet (malnourished) for 1 week when compared with rats fed a 25% casein diet (control). ODC activity increased progressively and reached a peak after 3 weeks of malnutrition and then decreased to control values by 5 weeks. RNA polymerase I reached peak activity 1 week after malnutrition was imposed, decreasing thereafter to control values by 3 weeks. At 4 and 5 weeks, RNA polymerase I activity in malnourished animals was lower than control. Nucleoplasmic DNA-dependent RNA polymerase activity remained unchanged in the first 2 weeks of malnutrition and decreased thereafter to values significantly lower than control. The data confirm our previous observations of cyclical changes during prolonged malnutrition and suggests a process of "biochemical adaptation" to malnutrition in which the organism enhances essential metabolic processes to maintain cellular homeostasis to the detriment of less essential functions like systemic growth.

KEY WORDS: • RNA polymerase • malnutrition • RNA metabolism • polyamines • ornithine decarboxylase

¹ Supported in part by National Institutes of Health Research Grant No. HD 06682.

² Presented in part at the 64th Annual Meeting of the Federation of American Societies for Experimental Biology, Anaheim, CA, April, 1980. Fed. Proc. 39: 1115, 1980. (Abstr. #4468).

³ Request for reprints should be addressed to: Dr. S. J. Rozovski, Institute of Human Nutrition, 701 West 168th Street, New York, NY 10032.

Manuscript received 21 September 1981.