Age-related growth of the spleen in normal and glucocorticoid treated rats.

1. Age-related changes in the growth, nucleic acid content and protein turnover of the spleen have been studied in normal male rats. 2. A rapid and marked atrophy of the spleen, was found 24 hr after exposure to cortisone or dexamethasone; increased rates of protein breakdown being primarily responsible. 3. Nonetheless, the total amount of protein synthesized in the spleen (measured in vivo) was significantly decreased (30-50%) 24 hr after exposure to these steroids. 4. This compared with only a 15% decrease in whole body protein synthesis, indicating a more pronounced hormonal effect on the spleen than on most other body tissues.