CHANGES IN LYMPHOCYTE SUBPOPULATIONS IN OTSUKA LONG-EVANS TOKUSHIMA FATTY RATS

The changes in the thymus, spleen and adrenal glands associated with a ge from 5 weeks to 12 weeks old and lymphocyte subpopulations in the t hymus and spleen were examined in the new strain of diabetic rats, Ots uka Long-Evans Tokushima Fatty (OLETF). Effects of restraint stress we re also compared with those in the control strain, Long-Evans Tokushim a (LETO) rats. The body weight, and weights of spleen and adrenal glan ds significantly increased with age in both strains, while the weight of the thymus in OLETF rats decreased although it increased in LETO ra ts. The percentage of CD4(+)CD8(-) increased and CD4(+)CD8(+) decrease d in the thymus with age in both strains, and these changes were signi ficantly enhanced in OLETF rats. The numbers of cells positive for nic k end-labeling in the thymus were greater in OLETF than in LETO rats a s shown by histological examination, although no significant differenc e was observed in the spleen or adrenal gland. The changes in lymphocy te subpopulations in the spleen, and the plasma corticosterone levels associated with age were comparable for both strains. The responses of these factors to restraint stress were not significantly different be tween the two strains. It has been suggested that the changes in T cel l subpopulations in the thymus of OLETF rats may be simply induced by the enhanced apoptosis associated with age.