Expression of type I and II receptors for transforming growth factor beta in the adult rat testis

After having established the specificity of the antibodies for the rat testis by western blot analysis, the potential target cells for transforming growth factors (TGFbetas) were identified by immunohistochemical detection of both type I (TbetaRI) and type II (TbetaRII) transducing receptors for TGFbetas in the adult rat testis in situ. Leydig cells showed a strong TbetaRII immunoreactivity whereas the TbetaRI staining was weak. Only TbetaRII was detectable in Sertoli cells. In germ cells, staining for TbetaRI was stronger than for TbetaRII and the expression of both receptors depended on the seminiferous cycle stage. TbetaRI first appeared in pachytene spermatocytes and was absent in elongated spermatids from stage XIV onwards. Labelling for TbetaRII was observed as early as the spermatogonia stage; it increased in pachytene spermatocytes at the onset of TbetaRI and disappeared in elongating spermatids from stage XI onwards. These results show that TGFbetas can affect somatic cells functions and suggest that these factors are involved in the control of meiosis and early spermiogenesis, exerting a direct effect on germ cells.