Effect of two sulfur-containing amino acids, taurine and hypotaurine in European sea bass (Dicentrarchus labrax) sperm cryopreservation

In the present work, taurine and hypotaurine were evaluated as potential additives to improve European sea bass (Dicentrarchus labrax) sperm quality after cryopreservation. For cryopreservation, three different extenders were used: control extender (NAM), supplemented with 1 mM taurine or supplemented with 1 mM hypotaurine, all of them containing 10% Me2SO as cryoprotectant. To evaluate sperm quality of fresh and thawed sperm, motility (CASA: computer assisted sperm analysis), viability (SYBR Green/propidium iodide), lipid peroxidation (malondialdehyde level), protein oxidation (carbonyl content), glutathione peroxidase, glutathione reductase and superoxide dismutase activities and DNA fragmentation (comet assay) were quantified. The result demonstrated that 1 mM hypotaurine supplemented extender increased total motility (30.1 ± 3.2%), and that 1 mM taurine extender produced higher velocity (18.1 ± 2.6 μm/s) and linearity (46.0 ± 4.8%) than the control extender (21.8 ± 3.2%, 15.5 ± 1.3 μm/s, 41.8 ± 2.4%, respectively). Cell viability, lipid peroxidation and protein oxidation were not statistically different between treatments. Similar results were obtained for glutathione peroxidase and superoxide dismutase activities. Only glutathione reductase showed differential activity before and after freezing, increasing its activity in thawed sperm. Regarding the comet assay results, taurine and hypotaurine significantly reduced DNA fragmentation (52.8 ± 0.9% and 51.8 ± 0.9%, respectively) in comparison to the control (55.7 ± 0.8%). In conclusion, for European sea bass sperm cryopreservation, extenders supplemented with 1 mM taurine and 1 mM hypotaurine improved some parameters of sperm quality after thawing, resulting in better motility and lower DNA damage than the control, two very important factors related to fertilization success.