Immunohistochemical Localization of Kisspeptin and Its Receptor in the Equine Ovary

Abstract

Kisspeptin is recognized for its role as the gatekeeper of reproduction in most mammalian species. However, its role in regulation of reproduction at the ovarian level is poorly understood in the horse. In this study, ovaries from follicular phase, luteal phase, anestrous period, and mares treated with ECP-sulpiride were subjected to immunohistochemistry to characterize kisspeptin-10 (Kp10) and its receptor (Kiss1r) protein expression throughout each reproductive stage and follicle type. Kisspeptin and receptor staining was detected in all follicle types (primordial, preantral, and antral) throughout all reproductive stages, as well as oocytes, corpora lutea, and ovulation fossa. The pattern of Kp10 and Kiss1r staining was affected by follicle type (P < 0.0001) and reproductive stage (P < 0.001). Kisspeptin-10 immunostaining intensity was greatest in antral follicles, with no differences (P > 0.05) between reproductive stages. Kisspeptin receptor immunostaining intensity was greatest in antral follicles, with no differences between reproductive stages except when comparing follicular phase to anestrous phase ovaries (P < 0.05). The results of this study indicate kisspeptin and its receptor may have potential roles in the period leading up to ovulation, as indicated by the intensity of immunostaining in antral follicles, follicular development, and steroidogenesis.