Lipid and antioxidant composition of chicken semen and its susceptibility to peroxidation

The antioxidant composition of the chicken seminal plasma and spermatozoa and the effect of sperm storage on fatty acid composition of the phospholipid fraction were investigated. Chicken semen displayed range of antioxidants including vitamin E, ascorbic acid, glutathione, superoxide dismutase and glutathione peroxidase. Ascorbic acid was almost equally distributed between seminal plasma and spermatozoa. In contrast, reduced glutathione and vitamin E were located mainly in the spermatozoa. The main form of glutathione peroxidase (GSH-Px) was Se-dependent GSH-Px, which was found in both the seminal plasma and the spermatozoa. On the other hand, superoxide dismutase (SOD) was mainly located (67%) in the spermatozoa. Cu,Zn-SOD was found only in seminal plasma but both forms of the enzyme (Cu,Zn-SOD and Mn-SOD) were found in spermatozoa. The toxic effect of H2O2 and cumene hydroperoxide on sperm motility was determined. Sperm incubation for 12 hours at 20 degrees C was associated with a significant decrease in the proportion of 22:4n-6 in the phospholipid fraction. The inclusion of Fe2+ in the incubation medium at 37 degrees C further increased the rate of lipid peroxidation as indicated by the significant decrease in the proportion of 20:4n-6, 22:4n-6, 22:5n-3 and 22:6n-3 in the phospholipid. Free radical-trapping activity of seminal plasma was measured. Possible mechanisms involved in sperm antioxidant protection are discussed.