Age-related growth and protein turnover in the thymus of normal and glucocorticoid-treated rats.

Age-related changes in the growth, nucleic acid content and protein turnover of the thymus have been studied in normal male rats. A rapid and massive atrophy was found at each age 24 h after exposure to cortisone acetate or dexamethasone; the thymus of sexually mature rats being most severely affected. The steroids decreased (70-90%) total protein synthesis in the thymus more than whole body synthesis (15%), indicating a more pronounced action on the thymus compared with other body tissues. Initially protein breakdown increased in the steroid-treated thymus but at longer times this change was reversed.