Abstract :
Semen manipulation and cryopreservation-thaw proceduresmayaccelerate the generation
of reactive oxygen species (ROS). Sperm exposure to large amounts of ROS has been shown
to cause membrane lipid peroxidation and cellular injury to the sperm. The objective of this
study was to overcome the ROS production in frozen-thawed ram semen by the addition of
the antioxidants catalase or Trolox to semen following thawing. Frozen-thawed ram semen
(100×106 sperm/straw) was supplemented with PBS (control group), 100 g/ml catalase,
or 100 MTrolox/108 sperm (catalase and Trolox being dissolved in PBS) and incubated
(37 ◦C) for 5 min. Under the experimental conditions used in this study, the catalase and
Trolox antioxidants failed to protect the sperm from the spontaneous production of ROS.
However, when lipid peroxidation was induced by iron (FeSO4), the addition of Trolox
promoted a reduction (P < 0.05) in the formation of TBARS in the semen, compared to the
control and catalase semen samples. The generation of TBARS and H2O2 occurred in the
extender alone, without the presence of sperm cells. In conclusion, the addition of Trolox
to frozen-thawed ram semen could be beneficial as it decreases the production of TBARS
when oxidative stress is induced. It is possible that a longer incubation period could lead
to different results. The concentration of catalase also needs to be further evaluated. The
extender could contribute to the oxidative stress of sperm, as it is a source of ROS during
the cryopreservation of semen.
