Progressive reduction in protein synthesis during involution and aging of the mouse thymus

Total proteolytic activity and protein synthesis were measured in cell-free extracts of the thymus during its involution in 1-30-week-old C57Bl/6J mice, and in 10-, 12-, 14-, and 24-month-old adult mice of the same strain. The mean specific activity of the proteolytic enzymes exhibited no significant change during involution or throughout the mean life-span of the animals. In contrast, the rate of protein synthesis decreased rapidly during involution, and continued to decrease at a slower rate during aging of the mice.