CONICET | Buscador de Institutos y Recursos Humanos

The biotechnology of reproduction in porcine species has poor development mainly due to the limitation in sperm cryopreservation. The availability of reliable markers of sperm function would provide tools to improve the cryopreservation process. In this way, our aim was to determine the activity of the enzyme lactate dehydrogenase (LDH; 1.1.1.27) and study its participation in the processes of the in vitro capacitation and acrosome reaction (AR) in cryopreserved porcine spermatozoa with alpha-tocopherol. Spermatozoa were incubated in TBM medium with bicarbonate and follicular fluid as capacitation and acrosome reaction inducers, respectively. Capacitation medium was supplemented with different concentrations of sodium oxamate (competitive inhibitor of the enzyme LDH). Capacitation and AR percentages were determined by the CTC technique and trypan blue combined with DIC, respectively. Sperm viability and motility were evaluated by the eosin/nigrosin technique and optic microscopy, respectively. The LDH activity was determined spectrophotometrically at 600 nm, during 2 minutes, at 37 °C and the enzyme unit (U) was defined as the amount of LDH that oxidizes 1 µmol of NADH/minute. The results were analyzed by ANOVA and Bonferroni test. The addition of the competitive inhibitor of the enzyme significantly (p<0.05) diminished capacitation and AR without affecting sperm viability, at different concentrations (1mM for capacitation and 0,5mM for AR). These concentrations also inhibited the activity of LDH (40 ± 5 and 73 ± 10 % of inhibition for 0.5 mM and 1 mM, respectively). Our results demonstrated the differential participation of the enzyme lactate dehydrogenase in the processes that are involved in the acquisition of the sperm fertilizing ability. This information can be useful for the formulation of incubation media to use in biotechnological reproduction techniques.