Abstract: The thymus index, microstructure, ultrastructure, thymocyte apoptosis ratio and the expression of several thymic cytokines and apoptosis-associated protein genes of mouse thymus were studied by using light microscope, electron micros-copy, flow cytometry, and real-time PCR technique during estrogen-induced thymus atrophy in mouse. The results indicatedthat in estrogen administration mouse, the thymus index decreased greatly, whereas the thymocyte apoptosis ratio increased signally; the expression level of thymic cytokines TGF-β1 increased greatly, IL-6 increased slightly, while IL-7 decreased obviously; the expression level of apoptosis-associated protein genes Caspase-3, Caspase-9 and FADD increased significantly, FasL increased slightly, while Bcl-2 decreased greatly. The results revealed that thymus atrophy in mouse was induced by estrogen possibly through inhibiting thymic epithelial cell proliferation by regulating the thymic cytokines on the one hand, and promoting thymocyte apoptosis by activting the initiatory and executive stages of Caspase cascade and the Fas/FasL-mediated apoptosis on the other hand.

Key words: estradiol; cytokine; apoptosis-associated protein; thymus; mouse