Efeito da adição de antioxidantes ao gradiente contínuo de densidade de percoll e ao diluidor de congelação sobre os espermatozoides caprinos selecionados e congelados

Abstract

It was aim to evaluate the effect of different concentrations of phenolic antioxidants on freezability of goats sperm, as well as their action during centrifugation in continuous Percoll density gradients and after selected semen freezing. Six goat semen pools were used for each of the three experiments. In the first two experiments, each semen pool was processed and diluted in the skimmed milk based extender (7 % glycerol), with or without antioxidants, according to experiment and experimental group [1 Experiment: 0, 15, 25, 50, 75 or 100 μM catechin or epigallocatechin gallate (EGCG); Experiment 2: 0, 15, 25, 50, 75 or 100 μM resveratrol or quercetin]. In Experiment 3, each semen pool was centrifugated in continuous Percoll density gradients and frozen (with or without antioxidants) according to experimental groups (NS=non selected; S= selected; SC75= selected with 75 μM catechin; SE100= selected with 100 μM EGCG; SQ25=selected with 25 μM quercetin; SR25=selected with 25 μM resveratrol; SR75=selected with 75 μM resveratrol). In Experiment 1, immediately after thawing, the straight linear velocity (VSL) and average path velocity (VAP) were greater (P<0.05) in 15 μM catechin than in 50 and 100 μM; wobble (WOB) was higher (P<0.05) in catechin 0, 15 and 25 μM than in 100 μM; beat cross frequency (BCF) was higher (P<0.05) in 75 and 100 μM catechin than in 0 μM. Progressive motility (PM) was greater (P<0.05) with 0 and 15 μM EGCG than with 50 and 75 μM; and linearity (LIN) was higher with 0 μM EGCG than with 100 μM. In Experiment 2 WOB was higher (P<0.05) in 0 and 25 μM resveratrol or 0 μM quercetin than 100 μM, immediately after thawing. In Experiment 3, immediately after sexing, PM, LIN, straightness (STR) and WOB from sexed groups were higher (P<0.05) than those from NS; SC75, VSL was higher (P<0.05) in SR25 and SR75 than in NS; amplitude of lateral movement of the head (ALH) was higher (P<0.05) in the NS than in other groups. SQ25 reduced (P<0.05) the mitochondrial membrane potential, compared to other groups. After thawing, PM, LIN, WOB, VSL and VAP were higher (P<0.05) in sexed groups than in NS, except to SE100 and SQ25; SC75 had greater (P<0.05) STR than NS; ALH was lower (P<0.05) in S, SC75, SR25 and SR75 than in NS; BCF was lower (P<0.05) in S than in NS; plasma membrane integrity was higher (P<0.05) in sexed groups than in NS, except to SE100; the percentage of intact and not dead cells was greater (P<0.05) in sexed groups than in NS. We concluded that, under the experimental conditions used, high concentrations (50 to 100 μM) of catechin inhibit the kinematics of frozen goat sperm in transitory way, and that resveratrol does not have any influence on goat semen freezability. Moreover, sex selection in continuous Percoll density gradients is feasible methodology to goats and compatible with freezing process; independent of antioxidant therapy used.