CELLULAR-DISTRIBUTION OF EGF, TGF-ALPHA AND THEIR RECEPTOR DURING POSTNATAL-DEVELOPMENT AND SPERMATOGENESIS OF THE BOAR TESTIS

The epidermal growth factor (EGF), the transforming growth factor alph a (TGF alpha) and the epidermal growth factor receptor (EGFr) have bee n immunolocalized, (i) during the testicular postnatal development (i. e. at the perinatal, prepubertal and adult periods), and (ii) during t he seminiferous epithelium cycle in the different germ cell types. Whi le TGF alpha was essentially observed in somatic cells, specifically i n perinatal Leydig cells and in mature Sertoli cells, EGF was localize d both in germ cells and in somatic cells with a preferential tubular expression. Furthermore, identification of EGFr in different testicula r cell types indicates that during postnatal development and spermatog enesis, testicular cells are potentially responsive to EGF in that the y express EGFr. Indeed, in the course of the gonadal development, the EGFr distribution was evidenced both in somatic and germ cells with a specific germ cell pattern depending upon the seminiferous epithelium cycle. A predominant EGFr staining was evidenced during the meiotic pr ocess and the spermiogenesis. Together, the present data are in favor of the involvement of the TGF alpha/EGF system in the local control of testicular cells during development and particularly of its potential direct implication in crucial steps of spermatogenesis such as meiosi s and spermiogenesis.