Effect of semen extender supplementation with cysteine on postthaw sperm quality, DNA damage, and fertilizing ability in the common carp (Cyprinus carpio)

Amino acids have an important biological role for prevention of cell damage during cryopreservation. The objective of this study is to determine the effects of cysteine on postthaw sperm motility, duration of sperm motility, DNA damage, and fertility in the common carp (Cyprinus carpio). Sperm collected from 10 individuals was cryopreserved in extenders containing different cysteine concentrations (2.5, 5, 10, and 20 mM). Semen samples diluted at the ratio of 1:9 by the extenders were subjected to cryopreservation. After dilution, the semen was aspirated into 0.25-mL straws; the straws were placed on the tray, frozen in nitrogen vapor, and plunged into liquid nitrogen. DNA damage was evaluated by comet assay after cryopreservation. Our results indicated that an increase in the concentration of cysteine caused a significant increase in the motility rate and duration of sperm in the common carp (C carpio; P < 0.05). Comparing all concentrations of cysteine, the best concentration of cysteine was 20 mM. Higher postthaw motility (76.00 +/- 1.00%) and fertilization (97.00 +/- 1.73%) rates were obtained with the extender at the concentration of 20 mM. Supplementation of the extender with cysteine was increased the fertilization and hatching rate and decreased DNA damage. Consequently, cysteine affected the motility, fertilization, and DNA damage positively, and extenders could be supplemented with cysteine. (C) 2015 Elsevier Inc. All rights reserved.