The expressions in oxytocin and sex steroid receptors in the reproductive tissues of normal and unilateral cryptorchid dogs.

In males, oxytocin is involved with various physiological functions, such as reproductive tract contractility and testicular steroidogenesis. Due to the relationship between sex steroid hormones, oxytocin receptor (OTR) expression and cryptorchidism pathogenesis, this study aimed to investigate the mRNA expression and the localization of OTR in relation to sex steroid receptors in the male reproductive tract of both normal and unilateral abdominal cryptorchid dogs using quantitative PCR and immunohistochemistry. Male dogs were divided into two groups of normal and cryptorchid dogs. Samples from each cryptorchid dog were separated into two subgroups: scrotal and abdominal subgroups. The results showed that a lower percentage of positive OTR immunostaining in the testis and epididymis was observed in the cryptorchid group compared to the normal group. Within the cryptorchid group, the mRNA expression and the localization of OTR in the testis and epididymis of the abdominal subgroup was less than that of the scrotal subgroup. Moreover, the localization of OTR and estrogen receptor beta (ERβ) in reproductive tissues was positively correlated only in the normal group and not in the cryptorchid group. In conclusion, this study proposed that OTR expression, as well as the correlation between the OTR and ERβ in reproductive tissues of male dogs, can be disturbed by cryptorchidism. Furthermore, the OTR, ERβ and their correlation may be involved with the pathogenesis of cryptorchidism. Therefore, the study of gene knockout models to confirm the effect of OTR and sex steroid receptors on canine cryptorchidism should be of interest for further investigation.