Addition of insulin-like growth factor I (IGF-I) and reduced glutathione (GSH) to cryopreserved boar semen

Abstract

The objective of this study was to evaluate the effect of adding reduced glutathione (GSH) to a boar semen freezing extender supplemented with insulin-like growth factor I (IGF-I) or anti-IGF-I. Eight ejaculates from eight boars were extended to obtain insemination doses, which were supplemented with either recombinant human IGF-I (30 ng/mL) or anti-IGF-I (60 ng/mL) shortly after extension. After 24 h of liquid storage at 17 °C, the semen was frozen with or without GSH (5 mM) in the freezing extender for a total of six treatments. Osmotic resistance and acrosome integrity was greater in fresh semen (P < 0.05) soon after adding IGF-I or the anti-IGF-I antibody. After 24 h of cooling, the supplementation with these compounds resulted in an increased (P < 0.05) percentage of sperm with relatively greater mitochondrial activity and reduced the percentage of cells with relatively greater concentrations of superoxide. After thawing, there was a reduction (P < 0.05) in the percentage and fluorescence intensity of sperm with greater quantities of superoxide and peroxide only in samples treated with GSH + IGF-I and GSH + anti-IGF-I. The addition of GSH (alone or in combination with IGF-I or anti-IGF-I), however, reduced the percentage of sperm with an intact acrosome (P < 0.05). The same effect was not observed with IGF-I or anti-IGF-I alone. In conclusion, the addition of IGF-I or anti-IGF-I improved the quality of fresh or liquid-stored semen. Using GSH in the freezing extender improved the antioxidant potential of frozen semen only in combination with IGF-I or an anti-IGF-I antibody.