Immunohistochemical localization of aromatase during the development and atresia of ovarian follicles in prepubertal horses

摘要

Ovarian steroidogenesis from the neonatal to pubertal period in horses is poorly understood This study was designed to immunolocalize cytochrome P450 aromatase in the ovarian follicles of slaughtered fillies ages approximately (I) 6-9 mo (<10MF), (II) I y (1YF) and (III) 1 5 y (1 5YF) The ovaries of adult mares were used as controls In each age group, immunoreactivity for P450arom was observed in the mural granulosa of nonatreric follicles >5 mm in diameter Staining intensity was dependent on the size and morphology of the follicle In nonatretic follicles 5-10 mm in diameter, the reaction was weak and heterogeneous while most intense staining was observed in preovulatory follicles In follicles (diameter <20 mm) in the groups <10MF and 1YF, the reaction was less Intense than in adult mare follicles of similar size In each age group several follicles with early or advanced signs of atresia exhibited a heterogeneous staining pattern, which subsequently disappeared in late atretic follicles No immunoreactivity was detected in the theca interna, preantral follicle or stroma cells Our observations reveal that the mural granulosa of viable follicles in fillies about 6-18 mo old contains aromatase, indicating that the ovary is capable of estrogen synthesis Immunoreactivity for P450arom was dependent on follicle size and disappeared in atretic follicles