Sperm maturation in dogs: sperm profile and enzymatic antioxidant status in ejaculated and epididymal spermatozoa

Spermatozoa become more susceptible to the attack of reactive oxygen species during maturation. To avoid oxidative damage, the epididymis must provide the necessary antioxidant protection. The aim of this study was to compare the canine sperm profile and the enzymatic antioxidant status of the ejaculated fractions and samples collected from the different segments of the epididymis (caput, corpus and cauda). Five adult dogs were used, and after 1-3 weeks, subsequently to bilateral orchiectomy and epididymal storage, sperm samples were collected from the different segments of the epididymis. Samples were evaluated for conventional microscopy and computer-assisted motility analysis: sperm plasma membrane permeability and the activity of the antioxidant enzymes catalase, glutathione peroxidase (GPx) and superoxide dismutase (SOD). Samples collected from the caput and corpus showed lower values for most of the motility variables evaluated, indicating different levels of immaturity. Catalase activity was observed only in ejaculated samples. Conversely, GPx activity was higher in the cauda epididymidis. Correlations were found between SOD and GPx and SOD and sperm motility in the epididymal cauda and corpus, highlighting the importance of the enzymes for the protection of spermatozoa during the transit along the epididymis.