Antioxidant status in fresh and cryopreserved sperm from gilthead sea bream (Sparus aurata)

Abstract

Cryopreservation may induce oxidalive stress on the sperm membrane, causing irreversible damage such as changes in membrane fluidity, enzymatic activity and further peroxidative insult affecting to DNA and other cellular structures. These findings are associated with a reduction in sperm motility, viability and fertilizing ability, due to a significant generation of reactive species (ROS) by spermatozoa (Aitken et aI., 1989a,b; de Lamirande and Gagnon, 1992). Superoxide dismutase (SOD), glutathione reductase (GSR) and glutathione peroxidase (GPX) are the main proactive enzymes, acting as scavenging agents that remove reactive species once formed. In fish spermatozoa there are no previous studies on the presence and activity of these enzymes, or how cryopreservation could affect their functionality. It is known that during freezing/thawing spermatozoa suffer different kind of stress that may be responsible for ROS production. Moreover, damage on sperm function can be minimized by addition of antioxidants to semen prior to cryopreservation (Bucak et aI., 2007), thus the evaluation of total oxidants in plasma samples may give some indication on further post-thaw sperm quality. The aim of the present work was to analyse total antioxidant levels (TAS) and the activity of glutathione peroxidase (GPX), glutathione reductase (GSR) and superoxide dismutase (SOD) in fresh and cryopreserved sperm.