Expression of GnRH, Kisspeptin, and Their Specific Receptors in the Ovary and Uterus in Deslorelin-Treated Late-Prepubertal Bitches

In this study, the expression and localization of gonadotropin-releasing hormone (GnRH1) and kisspeptin (KISS1) and their specific receptors in canine ovarian and uterine tissues were investigated after the application of deslorelin acetate (Suprelorin®, 4.7 mg, Virbac, France) in the late prepubertal period. We hypothesized that prolonged treatment of prepubertal dogs with deslorelin would alter the expression of GnRH and kisspeptin genes in the uterus and ovaries. Ovarian and uterine samples of 25 dogs with an average age of 7.8 ± 0.2 months and from mixed breeds were used. Following implant insertion, dogs entered estrus (EST; n = 6); dogs without estrus (N-EST; n = 10) comprised the experimental groups. Nine dogs with placebo implants served as a control (CONT). Ovarian and uterine tissues were investigated for expression of GnRH1, GnRHR, KISS1, and KISS1R/GPR54 mRNA and protein by using IHC and RT-qPCR. In the uterus, expression of GnRH1 significantly decreased in response to deslorelin treatment in the N-EST, compared with the control group. Compared with CONT, KISS1R expression in ovarian samples was significantly lower in the EST group. Uterine protein expression of GnRH1 appeared weaker in N-EST than in CONT. While GnRH1-system members and KISS1 protein were localized in the follicles at various stages and stroma, no or only weak signals were detected for KISS1R in the ovarian samples. Deslorelin-mediated induction of puberty by changing the expression of some of the GnRH and KISS1-system members seems to have an effect on ovarian and uterine functionality. Deslorelin implants can, therefore, not be considered a valuable alternative to induce fertile estrus in late-prepubertal bitches. However, further studies with a larger number of animals are needed to clarify the effect of deslorelin-mediated induction of puberty.