Role of residual cytoplasm on oxidative status during sperm maturation in dogs.

During maturation sperm cells acquire their fertilizing ability; however, this event also produces reactive oxygen species and as such local antioxidant protection is required. Thirteen epididymis from dogs were used, and sperm samples were collected from different segments of the epididymis (i.e. caput, corpus and cauda). The samples were evaluated for motility and vigor, permeability of plasma membrane, presence of cytoplasmic droplet, acrosome integrity and the activity of the antioxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD). Samples collected from the cauda showed higher motility, vigor and lower permeability of plasma and acrosomal membranes in relation to the corpus and caput, indicating different levels of maturity. The enzyme activity remained unchanged in the samples. A significant positive correlation was observed in the epididymal caput, between distal cytoplasmic droplet and SOD, and a negative correlation, in the epididymal cauda, between proximal cytoplasmic droplet and GPx, indicating the physiological need of the specific antioxidants in these segments.