Influence of the estrous cycle in the response of granulosa cells against bovine ovarian GnRH analogues in vitro

CAROU, MC.; CRUZANS, PR.; LOMBARDO, DM

Buenos Aires

Jornada; III Jornadas Internacionales del Instituto de Investigación y Tecnología en Reproducción Animal – INITRA; 2012

Instituto de Investigación y Tecnología en Reproducción Animal - INITRA. Facultad de Ciencias Veterinarias. UBA

Numerous studies show the presence of GnRH receptors (GnRHR) in granulosa cells (GC) of ovaries in different species. Its relationship with gonadal function was demonstrated by the induction of apoptosis "in vitro" and "in vivo" using different GnRH agonists. Our laboratory experiments on cells from bovine ovarian like the established line (BGC-1) that were incubated for 24 and 48 h, showed that the agonist, leuprolide acetate (LA) induced apoptosis in a dose dependent manner and increased significantly at 100 nM concentration. Our objective was to study the regulation of apoptosis by the LA in primary culture GC (CPGB) from bovine follicles. To this end we proceeded to analyze the regulation of apoptosis by the LA in a dose-response (1, 10 and 100 nM) curve at incubation time (24 and 48 hours) and the presence or absence of corpora lutea (CL). Two experiments were performed in triplicate and analyzed by two-way ANOVA and Bonferroni means comparison with a significance level of 5%. In CPGB, dose-dependent response against LA was variable, perhaps reflecting the degree of differentiation of GC (spontaneous luteinization in vitro). Two patterns were observed to respond to the induction of apoptosis by the LA. Cultures from ovaries with CL (luteal phase with P4 concentration greater than 0.8 ng / cell in the follicular fluid-FF, as determined by RIA) developed in direct response to the concentration of LA being significant at 100 nM (response type 1, similar to that observed in BGC-1), while crops from ovaries without CL (follicular phase or luteal regression, with concentrations less than 0.8 ng / cell in the FF) induction of apoptosis produced versus low doses of agonist (1 nM LA), type 2 response. We propose that according to the degree of GC differentiation they expressed different GnRHR conformations.