Ribonucleic acid metabolism in rat liver during long-term adaptation to malnutrition.
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.
D000222:Adaptation, Physiological; D000818:Animals; D002262:Carboxy-Lyases / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004044:Dietary Proteins / Q000008:administration & dosage; D008099:Liver / Q000378:metabolism*; D008297:Male; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D011073:Polyamines / Q000378:metabolism; D011502:Protein-Energy Malnutrition / Q000378:metabolism*; D012313:RNA / Q000378:metabolism*; D012318:RNA Polymerase I / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D004044:Dietary Proteins; D011073:Polyamines; D012313:RNA; D004247:DNA; D012321:DNA-Directed RNA Polymerases; D012318:RNA Polymerase I; D002262:Carboxy-Lyases; D009955:Ornithine Decarboxylase