Utilization of [1-14C]carbon of glycine of high glycine diet fed young and old rats.

The incorporation of radioactivity from [1-14C]glycine was studied into various organ (serum, liver, muscle) fractions (acid soluble, proteins, lipids, liver glycogen) and carbon dioxide in rats fed with isonitrogenous isocaloric purified diets. The diets contained 30% casein (control), gelatin (exchange of half of the 30% casein) or glycine (corresponding level of glycine in relation to the gelatin diet). The incorporation of radio-activity into proteins was reduced by feeding high glycine diets in young (20-weeks-old) and old (18-month-old) rats in relation to the control diet. The modifications of the results for old animals may be partially explained on the base of a reduced protein turnover rate and adaptation to a high gelatin (glycine) diet.