MOUSE EPIDIDYMAL SPERM CONTAIN ACTIVE P450 AROMATASE WHICH DECREASES AS SPERM TRAVERSE THE EPIDIDYMIS

Recently we reported that mouse germ cells in the testis contain activ e P450 aromatase (P450arom), the enzyme that converts androgens to est rogens. This finding suggested that germ cells have the ability to pro duce estrogen. Further studies have shown that germ cells in the testi s of several species contain P450arom. The goal of this study was to d etermine if epididymal sperm contain P450arom and if P450arom activity in sperm changes during traversion of the epididymis in the adult mou se. P450arom was localized in sperm present in the efferent ductules a nd epididymis by immunocytochemistry using an antiserum generated agai nst purified human placental cytochrome P450arom. P450arom immunostain ing in sperm was most prominent in sperm located in the proximal caput epididymis, decreased as sperm traversed the corpus epididymis, and w as only slightly apparent in sperm in the cauda epididymis. The immuno localization of P450arom in epididymal sperm was supported by the meas urement of P450arom activity in sperm by the (H2O)-H-3 assay. We found that P450arom activity in sperm significantly decreases as sperm trav erse the epididymis. Based upon these observations, we conclude that s perm can synthesize estrogen and that the synthesis of estrogen by spe rm present in the efferent ductules and caput epididymis could be impo rtant in the process of sperm maturation.