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.