Nitrogen balance studies in aging rats.
Nitrogen balance studies were conducted to compare the protein requirements of aged (24-month-old) and mature (12-month-old) rats for possible age-related differences. Four diets with protein supplied as amino acid mixtures simulating casein protein at 4.5%, 4.5% plus 1.5% indispensable amino acids of casein, 4.5% plus 1.5% dispensable amino acids of casein or 6.0% casein protein were offered for one week each during a four-week counter-balanced dietary sequence. Lower food and nitrogen intake of aged rats resulted in a lower mean nitrogen balance compared to that of the mature animals. Calculations of the level of N intake necessary to provide for N equilibrium in the aged rats indicated an apparent increase in the actual net need for nitrogen and indispensable amino acids when compared with the needs of the mature animals.
D000367:Age Factors; D000596:Amino Acids / Q000008:administration & dosage; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004044:Dietary Proteins / Q000008:administration & dosage; D005526:Food, Formulated; D008297:Male; D009584:Nitrogen / Q000008:administration & dosage* / Q000652:urine; D009751:Nutritional Requirements; D051381:Rats; D011916:Rats, Inbred F344 / Q000378:metabolism
D000596:Amino Acids; D004044:Dietary Proteins; D009584:Nitrogen