Mouse Epididymal Sperm Contain Active P450 Aromatase Which Decreases as Sperm Traverse the Epididymis

Abstract

Recently we reported that mouse germ cells in the testis contain active P450 aromatase (P450arom), the enzyme that converts androgens to estrogens. This finding suggested that germ cells have the ability to produce estrogen. Further studies have shown that germ cells in the testis of several species contain P450arom. The goal of this study was to determine if epididymal sperm contain P450arom and if P450arom activity in sperm changes during traversion of the epididymis in the adult mouse. P450arom was localized in sperm present in the efferent ductules and epididymis by immunocytochemistry using an antiserum generated against purified human placental cytochrome P450arom. P450arom immunostaining in sperm was most prominent in sperm located in the proximal caput epididymis, decreased as sperm traversed the corpus epididymis, and was only slightly apparent in sperm in the cauda epididymis. The immunolocalization of P450arom in epididymal sperm was supported by the measurement of P450arom activity in sperm by the 3H2O assay. We found that P450arom activity in sperm significantly decreases as sperm traverse the epididymis. Based upon these observations, we conclude that sperm can synthesize estrogen and that the synthesis of estrogen by sperm present in the efferent ductules and caput epididymis could be important in the process of sperm maturation.

Differential Expression of Genes Important to Efferent Ductules Ion Homeostasis across Postnatal Development in Estrogen Receptor-慣 Knockout and Wildtype Mice

“…The presence and expression of P450arom in the male reproductive tract of various species have been demonstrated from a number of laboratories (Nitta et al, 1993;Kwon et al, 1995;Janulis et al, 1996;Tsubota et al, 1997;Janulis et al, 1998;Carreau, 2000). In the mature rat testis, the presence of P450arom is localized in Leydig and Sertoli cells (Papadopoulos et al, 1986), whereas the Sertoli cells synthesize estrogen in the immature rat testis (Carreau et al, 1999).…”

“…We used a 1:400 dilution of polyclonal rabbit anti-human placental P450arom (Hauptman-Woodward Medical Research Institute Inc., Buffalo, New York) as a primary antibody. This antibody was previously used to detect the expression of P450arom in the mouse testis and epididymal sperm in mouse and rat (Nitta et al, 1993;Janulis et al, 1996;Janulis et al, 1996). After incubation at 4°C for overnight with the primary antibody in a humidified chamber, sections were washed with PBS and treated with biotinylated antirabbit IgG secondary antibody (Vectorostain kit, Vector Laboratories, Burlingame, CA) for 1 h at room temperature in a humidified chamber, followed by addition of elite avidin-biotin peroxidase complex (Vector Laboratories, Burlingame, CA) for 30 min at room temperature in a humidified chamber.…”

“…In the mouse, P450arom is first detected in pachytene spermatocytes and then the more mature germ cells (Nitta et al, 1993). In addition, spermatozoa in the excurrent ducts possess P450arom (Kwon et al, 1995;Janulis et al, 1996;Janulis et al, 1998). In the developing mouse testis, different germ cell populations appear chronologically at different ages.…”