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The aim of this work was to study the participation of lactate dehydrogenase (LDH) enzyme in capacitation and acrosome reaction in porcine sperm by determining its enzymatic activity and the effect of its inhibition on these processes. Semen samples, from four crossbred boars (Pietrain x Yorkshire) of proven fertility, 1-1.5 year of age, were analysed. The enzymatic activity of LDH was determined spectrophotometrically in extracts from fresh and cryopreserved, with and without α-tocopherol, porcine sperm. Besides, sperm suspensions were incubated in the presence of bicarbonate (40 mM), a well-known capacitation inducer, follicular fluid (30%), as an acrosome reaction inducer, and different concentrations of sodium oxamate, a specific inhibitor of the enzyme. The activity of LDH in enzymatic extracts of fresh, cryopreserved without or cryopreserved with α-tocopherol porcine sperm were 3.85±0.27, 0.7±0.04 and 1.73±0.23 U/1010 sperm, respectively (p<0.05). The addition of sodium oxamate inhibited capacitation or acrosome reaction in fresh and cryopreserved with or without α-tocopherol porcine sperm, affecting (at different concentrations) motility and sperm viability (P<0.05). Obtained results demonstrate the participation of LDH in bicarbonate-induced capacitation and follicular fluid-induced acrosome reaction in fresh and cryopreserved porcine sperm. [ABSTRACT FROM AUTHOR]

Ejaculates of four crossbred boars were frozen with or without 200 µg/mL of α-tocopherol. Frozen samples were then thawed in the extender containing either ascorbic acid (2.5, 5 or 10 mM) or pyruvate (1 or 5 mM) to obtain the samples in which sperm quality parameters and lipid peroxidation level were evaluated. Ascorbic acid decreased lipid peroxidation in a dose-dependent manner and increased post-thaw sperm motility. The addition of pyruvate decreased lipid peroxidation level without improving sperm quality parameters. Although the addition of ascorbic acid or pyruvate did not show a synergic effect with α-tocopherol, the decrease of lipid peroxidation observed when the antioxidants were added to the thawing extender could be indicating a protective effect on the sperm plasma membrane from peroxidative damage. Since α-tocopherol protects from the lipid peroxidation and improves the sperm motility, it would be considered as the recommended antioxidant to use in boar sperm cryopreservation to extend the time of storage for the use in commercial applications. [ABSTRACT FROM AUTHOR]