Phospholipid fatty acid composition, vitamin E content and susceptibility to lipid peroxidation of duck spermatozoa

Recent studies on chicken semen have suggested that the lipid and fatty aci d composition of spermatozoa may be important determinants of fertility. Ph ospholipid fatty acid composition, vitamin E content and in vitro susceptib ility to lipid peroxidation of duck spermatozoa were investigated using CC- MS and HPLC based methods. The total phospholipid fraction of duck spermato zoa was characterized by high proportions of the n-6 polyunsaturated fatty acids arachidonic (20:4n-6), docosatetraenoic (22:4n-6) and docosapentaenoi c (22:5n-6) acids but a substantial proportion of the n-3 fatty acid docosa hexaenoic (22:6n-3) acid was also present. Palmitic (16:0) and stearic (18: 0) fatty acids were the major saturates in sperm phospholipids. Among the p hospholipid classes, phosphatidylserine (PS) had the highest degree of unsa turation due to very high proportions of 22:6n-3, 22:5n-6, 22:4n-6 and 20:4 n-6, comprising together more than 75% of total fatty acids in this fractio n. Phosphatidylethanolamine (PE) also contained high proportions of these f our C20-22 polyunsaturates, which together formed 60% of total fatty acids in this phospholipid. Spermatozoa and seminal plasma of duck semen were cha racterized by unexpectedly low content of vitamin E, being more than 4-fold lower than in chicken semen. In duck semen the major proportion of the vit amin E (>70%) was located in the spermatozoa. The very high proportion of 2 2:6n-3 in PS and PE fractions of duck sperm lipids and the comparatively lo w levels of vitamin E could predispose semen to lipid peroxidation. Neverth eless the in vitro susceptibilities to Fe2+-stimulated lipid peroxidation o f duck and chicken spermatozoa were very similar. The results of the study suggest that increased superoxide dismutase and glutathione peroxidase acti vity and increased antioxidant activity of seminal plasma may compensate fo r the low levels of vitamin E to help protect the membranes of duck spermat ozoa, which exhibit a high degree of unsaturation from oxidative stress. (C ) 2000 by Elsevier Science Inc.