Function and regulation of TGF beta members during final follicular growth and ovulation in cattle

Antral follicle development culminates with ovulation and, in monovulatory species, only one follicle is selected to grow whereas all the others undergo atresia. During these processes, all the follicles are under the same endocrine environment, indicating the participation of locally produced factors in the regulation of follicular growth and differentiation. In this context, the involvement of transforming growth factors-beta (TGF-β) family members and their receptors is highlighted. Despite their high relevance, the real functions of TGF-β proteins in ovarian physiology is still poorly understood. In this regard, the aim of this study was to gain insight into the function and regulation of ovarian factors, investigating the function of growth and differentiation factor 9 (GDF9) during dominant follicle growth. Furthermore, we tested the hypothesis that TGF-β members, especially bone morphogenetic proteins (BMPs) and their receptors are regulated during luteinization and ovulation processes in cattle. In a first experiment, the intrafollicular injection of GDF9 in dominant follicles (9±0.2 mm diameter) at final concentrations of 100 and 1000ng/mL did not affect follicular growth, estrus manifestation and ovulation (P>0.05). In a second study, using granulosa cells from preovulatory follicles (>12mm), collected in vivo at different time-points (0, 3, 6, 12 and 24 h) after GnRH treatment, mRNA expression of BMPs 1 and 4 was not regulated. By the other size, BMP2 expression was significantly upregulated at 3 and 6 h (P0,05). No segundo estudo, utilizando células da granulosa provenientes de folículos pré-ovulatórios (>12 mm), coletados in vivo em diferentes momentos (0, 3, 6, 12 e 24 h) após aplicação i.m de GnRH, a expressão de RNAm das BMPs 1 e 4 não foi regulada. Por outro lado, a expressão de BMP2 aumentou significativamente 3 e 6 h após GnRH (P