Objectives: To examine the localization and expression of the c-kit receptor protein in the testes of the mouse, rat, and human, and then compare these among the three species.
Methods: Testis tissue from all three species was obtained through biopsy or orchiectomy. Immunohistochemistry was used for the localization, using a monoclonal antibody to the c-kit receptor. The expression of the c-kit receptor protein was examined in the testes and sperm with Western blot analysis.
Results: Localization was noted in the early spermatogenic cells, most likely type A spermatogonia, as well as in the acrosomal region of more mature germ cells, such as the round spermatids. The c-kit receptor was localized in analogous sites in all three species. The Western blot data revealed testicular expression of the c-kit receptor protein in all three species as well. Similar bands were recognized on the Western blots of all three species in testes at approximately 75 kDa and approximately 90 kDa, and sperm at approximately 90 kDa only.
Conclusions: The c-kit receptor protein is expressed in the early spermatogenic cells, as well as the later stages of spermatogenesis, specifically, the acrosomal granules of the round spermatids, and the acrosomal region of testicular spermatozoa, in the mouse, rat, and human. All three species exhibit similar expression of the c-kit receptor protein in both testis and sperm, although to a varying degree. We believe that these observations allow direct valid comparisons concerning the expression of the c-kit receptor to be made cautiously to the human condition from experimental data obtained from rodents.