O-46: The Expression of Leptin and Its Receptorduring Different Physiological Stages in theBovine Ovary

Background: Leptin, the hormonal product of the obese (ob) gene, circulates in the blood at levels paralleling those of fat reserves and regulates satiety. In cattle, leptin has also been implicated in the control of ovarian function, but its local production in the ovary and role in the control of ovarian function in autocrine/paracrine manner is unknown. The aims of this study were to document the expression of leptin and its receptor (Ob-R) in detail in bovine corpus luteum (CL) obtained from different stages of the oestrous cycle and during pregnancy and to determine if the leptin/Ob-R system is expressed clearly in bovine follicles during final growth to preovulatory follicles. Materials and Methods: Experiment 1: corpora lutea (CL) were assigned to the following stages: days 1-2, 3-4, 5-7, 8-12, 13-16, and >18 of oestrous cycle and of gravidity (month 8). Experiment 2: Follicles during maturation were divided into granulosa cells (GC) and theca interna (TI) and were examined separately. Classification of follicles occurred by follicle size and oestradiol-17β (E2) concentration in the follicular fluid (FF) (180 ng/ml). Real-time RT-PCR (qPCR) and ELISA were applied to investigate mRNA expression of examined factors and leptin protein respectively.Results: In general, we demonstrated leptin and its receptor transcripts and leptin protein are consistent with in vivo luteinisation of bovine CL and decline coincidental with luteal regression. The highest co-expression of leptin/Ob-R system was observed in TI and GC of the smallest follicles with E2 concentration