IMMUNOHISTOCHEMICAL LOCALIZATION OF TRANSFORMING GROWTH FACTOR-BETA(1) IN THE FETAL AND NEONATAL RAT TESTIS

The localization of transforming growth factor-beta(1) in the fetal an d neonatal rat testis (from day 13.5 of fetal life to postnatal day 20 ) was investigated by an immunohistochemical staining method employing a polyclonal anti-TCF-beta(1) antibody that does not cross react with either TGF-beta(2) or TGF-beta(3). In testis and mesonephros tissue, immunostaining for TGF-beta(1) was undetectable on fetal day 13.5 and appeared exclusively in the primordial Sertoli cells on fetal day 14.5 . Staining in Sertoli cells was still clearly observed on days 15.5 an d 16.5 of fetal life and became faint from fetal day 18.5 onwards. In fetal Leydig cells, a positive reaction for TGF-beta(1) appeared on da y 16.5 and became very intense during late fetal life. After birth, fe tal-type Leydig cells, which were still observed on postnatal days 4 a nd 20, also exhibited a very strong immunostaining for TGF-beta(1), wh ereas adult-type Leydig cells, observed on day 20, showed a slight sta ining. No immunoreactivity for TGF-beta(1), was found in germ cells an d peritubular cells on any day studied. In conclusion, TGF-beta(1), is present very early in the fetal rat testis and its prevailing localiz ation shows age-related changes, which suggests that this factor plays an autocrine/paracrine role in the regulation of testicular function and differentiation, during early development.