Concomitant studies on RNA and protein syntheses in tissues of rats of various ages

Abstract

Concomitant in vivo studies on RNA and protein syntheses in the liver, muscle, heart, brain, kidney, testis and spleen of 11, 40 and 89 week old male rats were conducted using ¹⁴C-leucine respectively. Some of the significant findings are that (1) the rates of syntheses of RNA and protein change with age in different tissues; (2) the patterns of these changes are similar in the liver, heart, skeletal muscle and kidney, whereas those of the brain, spleen and testis are different; (3) even though the concentration of RNA in all the tissues is highest at 89 weeks, the rate of protein synthesis is lower than at 40 weeks. The possible cause(s) of these changes may be that (a) the fraction of translatable mRNA may be lower in old age; (b) rRNA synthesis may change with age; (c) the types of mRNA and the rates of their syntheses may change with age due to the need for different isoenzymes and other proteins not present in earlier ages.