EXPRESSION AND LOCALIZATION OF INDUCIBLE NITRIC-OXIDE SYNTHASE IN THERAT OVARY - A POSSIBLE INVOLVEMENT OF NITRIC-OXIDE IN THE FOLLICULAR DEVELOPMENT

In the present study, using Northern blot analysis, we demonstrated th at the level of iNOS mRNA in the ovary of immature rats decreased afte r 6 h of pregnant mare serum gonadotropin administration and recovered gradually up to the untreated level 48 h after the administration. Bo th in situ hybridization and immunohistochemistry revealed that iNOS m RNA and protein was predominantly localized in granulosa cells in most of immature follicles, but not in mature follicles with an antrum, wh ich was a consistent finding regardless of gonadotropin treatment, Fur thermore, we found that cultured granulosa cells had the ability to ex press iNOS mRNA in the presence of cytokines such as tumor necrosis fa ctor-alpha, interleukin-1 beta and interferon-gamma, which are inheren tly detectable in the ovary. These results raise the possibility that locally produced NO synthesized by iNOS may be involved in the develop mental status of ovarian follicles in concert with gonadotropin. (C) 1 998 Academic Press.