PARENT SESSION
Follicular Development
102
IN VIVO EFFECT OF A GONADOTROPIN RELEASING HORMONE AGONIST ON THE EXPRESSION OF BCL-2 FAMILY MEMBERS AND STEROIDOGENIC PROTEINS IN PREOVULATORY RAT OVARIAN FOLLICLES.
Tesone, Marta1, Parborell, Fernanda1, Irusta, Griselda1, Pecci, Adali2, Vitale, Alejanda1, 1 2
ABSTRACT- Gonadotropin-releasing hormone (GnRH) and its agonists, have specific effects on extra-pituitary tissues such as placenta, breast and ovary. A GnRH-like peptide, as well as GnRH receptor and GnRH gene transcription products, have been identified in the ovary. In addition, we have demonstrated the antigonadal effect of GnRH agonist in human and rat granulosa/luteal cells. In the present studies, we have determined the in vivo effects of the GnRH agonist (leuprolide acetate, LA) on the regulation of apoptosis in microdissected preovulatory ovarian follicles (POF) obtained from 2 day prepubertal pregnant mare serum gonadotropin (PMSG) treated superovulated rats. POF from LA rat ovaries show a significant increase in apoptotic DNA fragmentation as measured by the terminal deoxynucleotidyl transferase-mediated deoxyuridine nick end-labeling technique (TUNEL) (control C: 0.65± 0.19; LA: 6.11± 1.41 apoptotic cells/camp) and by agarose gel electrophoresis (C: 450.5±10.5; LA: 1707.8±16.5 arbitrary units). Gene expression of some members of the bcl-2 family and proteins involved in steroidogenesis were studied by Western analysis. LA did not alter bcl-2 expression (antiapoptotic protein) after 0, 1 and 2 h of POF incubation in serum- free medium, but bax levels (proapoptotic protein) were higher in the POF obtained from LA treated rats (0 h: 50%; 1 h: 207%; 2 h: 57%). LA also increased the levels of the steroidogenic acute regulatory protein (StAR) but decreased the P450scc follicular protein content. It is concluded that LA- induced apoptosis in rat preovulatory follicles is mediated by changes in the expression of some bcl-2 family members and in at least some steroidogenic protein levels.
KEY WORDS: OVARIAN FOLLICLE, GNRH AGONIST, APOPTOSIS, STEROIDOGENIC PROTEINS