Abstract: Objective：Calretinin(CALB2), a calcium-binding protein, may be expressed in human testes, suggesting that CALB2 can play roles in regulating testicular functions. This study was designed to explore the different expression of CALB2 in the testes of rats at different development stags, and to discuss its role in regulating androgen production. Methods：The 3-4-week-old SD male rats as group A（the pre-sexual maturity, n=35），16-week-old as group B（the sexual maturity, n=16）， and over-12-month as group C（the older rats, n=10）were used in the study. Sera testosterone concentration was detected by radioimmunoassay（ＲＩＡ）.Cellular location of CALB2 in testes was observed by immunohistochemistry. Expression levels of CALB2 mRNA and protein were quantificationally analyzed by qPCR and western blot. Results: CALB2 was mainly located in the cytoplasm of Leydig cells. Sera testosterone level was the lowest in the group A, and the highest in the group B（P＜0.05）. Compared to the group A and the group C, expressions of CALB2 were significantly increased（P＜0.05）. Conclusions: Calretinin is located in the cytoplasm of Leydig cells, and differently expressed in testes of rats at different development stages, which suggested that calretinin regulated testosterone production.

Key words: Androgens, Testis, Leydig cells, Calcium-binding protein, vitamin D-dependent