323 POSSIBLE BENEFICIAL EFFECT OF REACTIVE OXYGEN SPECIES ON BOAR SPERM FUNCTION

Abstract

Boar spermatozoa are sensitive to the attack of reactive oxygen species (ROS) due to the high content of unsaturated fatty acids in its plasma membrane and the relative low antioxidant capacity of boar seminal plasma. The benefical effect of antioxidant supplementation to the semen of boars is still a matter of debate, with different results in the literature, probably due to the empirical methods used to determine the more adequate antioxidant, and to the physiological role or the ROS. The aim of the present experiment was to study which ROS is the most deleterious to the boar sperm. Sperm samples from 4 boars were collected by digital manipulation. Sperm samples were then incubated (1 h, 37°C) with 4 ROS inducer mechanisms: xanthine/xanthine oxidase (produces superoxide anion), hydrogen peroxide (4 mM), ascorbate/ferrous sulfate (4 mM; produced hydroxyl radical), and malondialdehyde (lipid peroxidation product). Samples were analyzed for the 3-3′ diaminobenzidine stain, as an index of mitochondrial activity; the eosin/nigrosin staining, as an index of membrane integrity; the simple stain (fast green/Bengal rose), as an index of acrosome integrity; and the measurement of thiobarbituric acid reactive substances (TBARS), as an index of lipid peroxidation. Results showed that the boar sperm is relatively resistant to all ROS studied in the present experiment. Only for the percentage of sperm showing intact membrane, a difference was found between incubation with superoxide anion and hydroxyl radical (Table 1). The TBARS production was higher in samples incubated with hydroxyl radical, indicating that these samples were more susceptible to the attack of this ROS. Surprisingly, a positive correlation was found between TBARS and membrane integrity (r = 0.51, P = 0.04), indicating that samples more susceptible to the oxidative stress showed higher membrane integrity. A hypothesis to explain such conflicting results would be the physiological role of the ROS on several spermatic events, especially in this particular species. It is well known that boar semen, in order to achieve ideal motility, requires aerobic conditions. Further studies are necessary to study the effect of each ROS on each physiological or pathological event on boar sperm function.

Table 1.  Effect of different ROS in boar semen

The authors thank Nutricell for the media used in the present experiment.