Peptidase activity in the thymus of a normal and a leukemic strain of mice during growth and aging.

A characteristic of the normal thymus gland is its rapid growth during the early stages of life followed by a progressive involution as the animal ages. On the other hand, in the Akr strain of mice a marked hyperplasia of this gland usually occurs in those animals which develop lymphatic leukemia. In this strain the thymus is believed to be the primary site of leukemogenesis (6). In the following study one metabolic aspect of the thymus, namely, the rate at which thymus homogenates hydrolyze the tripeptide glyeylglycylglycine, was examined. The object was to find out (a) how the peptidase activity per unit weight of thymus varies throughout the life span of normal mice, (6) whether the peptidase activity of the thymus from the leukemic strain of mice differs from that of normal mice at comparable ages, and (c) whether a difference exists between the pepti dase activity of the glands from the leukemic strain of mice which develop leukemia and those which do not. Preliminary to this a study of the characteristics of the hydrolysis of triglycine by thymus homogenates was undertaken.