Spermatogenesis in the golden hamster: the role of c-kit.

c-kit is related to the family of transmembrane tyrosine kinase receptors. Mutations in genes for either c-kit or its ligand, Steel factor, result in infertility, but the role of c-kit/SCF system in spermatogenesis is not well understood. In this study Western blot analysis together with confocal microscopy were used to follow c-kit expression in hamsters during the first spermatogenic wave in mature animals and in old age. Three antibodies raised against different domains of c-kit were tested on Western Blot. Confocal microscopy was performed after incubation of fixed seminiferous tubules with tested antibodies followed by binding of FITC-labeled secondary antibody. Longitudinal sections of seminiferous tubule were observed by confocal microscopy to determine in which stages of spermatogenesis and in which cell types c-kit was found. C-kit bands of 80,140, and 150 kDa were observed on Western blot, indicating that c-kit is a name related to several proteins sharing some common domains. Only the band of 150 kDa correlated with positive staining of c-kit in tubules using confocal microscopy. We term this protein c-kit150T (150 kDa, testis). We demonstrated that c-kit150T appeared in differentiating hamster spermatogonia at stages VII-VIII of adult spermatogenesis and at day 13-14 during the first spermatogenic wave. It remained attached to the cell until late pachytene. This suggests that c-kit may play a role in preparing the germinal cells to enter meiosis. In order to evaluate the effect of aging on the number of germ cells, B2 spermatogonia/Sertoli cell ratio was calculated in the group of young animals (5-7 months) compared to this ratio in older ones (20-26 months). A significant decrease (P < 0.01) in the number of B2 spermatogonia in the group of old hamsters as compared to young ones was seen. The calculated value for the B2 spermatogonia/Sertoli cell ratio was 5.6 +/- 0.7 in young animals and 3.8 +/- 1.2 in the 20-26 months ones. In addition, decrease in the intensity of staining for c-kit was detected in the old hamsters. These may be the reasons for subfertility in old age and in other cases of testicular disorders. Copyright 2001 Wiley-Liss, Inc.