Reproduction Abstracts

Introduction: Kisspeptin, a neuropeptide secreted in the hypothalamus and encoded by the Kiss-1 gene, has a role in promoting the release of GnRH and LH in various species. However, the possibility that kisspeptin exerts additional ‘peripheral’ actions at the level of the bovine gonad has not been investigated. The current aims were to investigate whether: i) kiss-1 and its receptor (GPR54) are expressed in the bovine ovary; ii) kisspeptin or kisspeptin antagonist can modulate ovarian steroidogenesis by cultured theca (TC) and granulosa (GC) cells.

Methods: GC (n=38) and TC (n=43) samples retrieved from bovine antral follicles (2–18 mm) were categorized into five size classes. Early, mid and regressing corpora lutea (CL) were also collected. Total RNA was harvested for qPCR analysis and data were analysed using the ΔΔCT method using β-actin for normalization. Bovine TC and GC cultured under both non-luteinized (±LH or FSH) and luteinized (± Forskolin) conditions were treated for 4 days with Kisspeptin-10 (10⁻¹⁰–10⁻⁶M), Kisspeptin antagonist (K234; 10⁻¹⁰–10⁻⁶M) or a combination of the two. Steroid secretion (androstenedione, oestradiol, progesterone) was measured by ELISA and viable cell number determined by neutral red uptake assay. Results are based on 3-6 independent cultures.

Results and discussion: Kiss-1 and GPR54 transcripts were detected in all TC, GC and CL samples with significant differences between follicle categories (P<0.001) and CL stages (P<0.05). However, TC/GC culture experiments using kisspeptin or its antagonist offered no evidence to support the hypothesis that kisspeptin has a direct intra-ovarian role to modulate follicular or luteal steroidogenesis or cell proliferation/survival.