Addition of resveratrol on boar insemination doses decreases lipid peroxidation but increase fluidity of membrane lipids

Lipid components located in the sperm membranes are deeply involved in sperm functions. The sperm cell metabolism spontaneously produces a plethora of reactive oxygen species (ROS). When ROS production exceeds the sperm's limited antioxidant defenses, a state of oxidative stress is induced affecting the peroxidation of sperm lipids and others sperm; functions. The production of low quantities of ROS plays an important role on normal sperm functioning, but disproportionate levels can impair sperm capacitation affecting negatively the quality of spermatozoa. Resveratrol (RVT) is a polyphenol compost with an intense capacity to inhibit ROS formation and consequently prevent excessive lipid peroxidation. The current study was design to evaluate whether the addition of the antioxidant RVT would influence positively membrane fluidity and lipid peroxidation of boar semen cooled at 17˚C for 72 h. Thus, six ejaculates from six boars (n=36) were collected. After initial raw semen analysis, samples were extended in BTS medium (50 x 106 spermatozoa/mL) and RVT was added, resulting in the following treatments: T0 (BTS + RVT 0 mM), T1 (BTS + RVT 0.01 mM), T2 (BTS + RVT 0.1 mM) and T3 (BTS + RVT 1 mM). Treatments were cooled and membrane fluidity and lipid peroxidation were accessed by flow cytometer after 0, 24, 48 and 72 h. There was no interaction between time and treatment for membrane fluidity (p>0.05). Addition of 0.01mM and absence of RVT (T2 and T1, respectively) were less harmful for sperm cells than 1mM (2875.21 ± 225.10c ; 3031.41 ± 195.55bc; 3225.81 ± 202.43ab; 3627.58 ± 271.90a ; data in mean fluorescence intensity [arbitrary units] for T0, T1, T2 and T3, respectively). Regarding to membrane lipid peroxidation, an interaction between time and treatment was observed (p<0.05). The highest concentration of RVT decreased peroxidation of membrane lipids only 72 h after cooling at 17˚C (0 hours: 3205.35 ± 93.80a ; 3249.28 ± 112.87a ; 3260.88 ± 120.51a ; 3104.03 ± 75.76a ; / 24 hours: 3351.11 ± 94.22a ; 3141.77 ± 67.66a ; 3237.14 ± 96.95a ; 3257.38 ± 127.47a ; / 48 hours: 3357.76 ± 121.28a ; 3349.78 ± 116.52a ; 3554.14 ± 158.30a ; 3393.38 ± 163.90a ; / 72 hours: 3244.30 ± 56.28a ; 3176.39 ± 36.15a ; 3160.24 ± 44.23a ; 2979.16 ± 39.17b ; data in mean fluorescence intensity [arbitrary units] for T0, T1, T2 and T3, respectively for each time). Concentrations higher than 1mM of RVT decreases membrane lipid peroxidation of sperm cells, but on the other hand, increases considerably membrane fluidity, impairing lifespan of sperm. In conclusion, despite the damage on sperm membrane lipid peroxidation have been decreased by addition of 1mM of RVT from 72 h, high concentrations of RVT alters the fluidity of membrane lipids increasing capacitation-like changes of sperm cells.