R Narenji Sani - Department of Basic Sciences, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran.
P Tajik - Department of Theriogenology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.
M.H Yousefi - Department of Basic Sciences, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran
M Movahedin - Department of Anatomical Sciences, School of Medical Sciences, Tarbiat Modarres University, Tehran, Iran.

BACKGROUND: The complex process of spermatogenesis is regulated by various factors. Studies on spermatogonial stem cells have provided a very important tool to improve herd genetic and different field. 0.2 to 0.3 percent of total cells of seminiferous tubules consist of spermatogonial stem cells. To investigate andbiomanipulate these cells, first the proliferation and viability rate of cells should be increased in vitro. OBJECTIVES: In the present study, the in vitro effects of testosterone on spermatogonial cell colony formation were investigated. METHODS: Sertoli and spermatogonial cells were isolated from 3-5-month-old calves. The identity of the cells was confirmed through analysis of immunocytochemistry. Co-cultured Sertoli and spermatogonial cells were treated with testosterone in different doses of 0.2 μmol L-1, 0.4 μmol L-1 and 0.8 μmol L-1, before colony assay. RESULTS: testosterone did not decrease the proliferation of spermatogonial stem cells. CONCLUSIONS: testosterone can be chosen for in vitro colonization of spermatogonial cells with other factors

co-culture, bovine, testosterone