Changes in thymocytes due to aging--a study of the effects of thymic hormone on adenine nucleotides and thymocyte DNA.

The number of lymphocytes (especially T-lymphocytes) in peripheral blood decreases with aging. The decline is most evident in the thymus. In this study, total AN in the thymocytes of aged mice clearly decreases from that of young mice. The quantity of thymic hormones secreted by thymic cells decreases with the organism's thymus involution with age. After demonstrating the decrease in total AN (primarily ATP) levels within the thymocytes of aged mice, we attempted to reattain the levels of younger thymocytes by the administration of various thymic hormones. Examination of DNA in the thymocytes of 4 and 58-week-old mice, using flowcytometry, showed no differences in content. However, it is significant that aged mouse thymocytes's energy level can be returned to those of young mice with the application of Th-5.