Rooster testicular germ cells and epididymal sperm contain P450 aromatase

We recently found that cytochrome P450 aromatase (P450(arom)) is present in germ cells of the mammalian testis and is capable of converting androgens to estrogens in the male reproductive tract. The objective of the present study was to determine whether testicular germ cells and epididymal sperm of an avian species are also capable of synthesizing estrogen. P450(arom) was localized in the rooster testis and epididymal region by immunocytochemistry, using an antiserum generated against purified human placental cytochrome P450(arom). Immunostaining was present in pachytene spermatocytes, round spermatids, elongated spermatids, flagella of late spermatids, and sperm in the epididymal region. A positive reaction was also found in nonciliated cells of the epididymal region. However, the absence of mRNA for P450(arom) in the epididymal region indicated that the immunoreactive protein present in the epididymal region is not synthesized in this region. The immunoreactive P450(arom) found in epididymal sperm was shown to be active through use of a ³H₂O assay. On the basis of these data, we conclude that rooster testicular germ cells and epididymal sperm a re sites for the synthesis of estrogen, a potential regulator or modulator of germinal epithelium in the testis and the epithelium of the epididymal region of the avian species.