USE OF VITAMIN C COMBINED TO PENTOXIFYLLINE AND FERTILITY IN CATTLE AFTER CRYOPRESERVATION
The process of frozen of the sperm provides a resting state of the cell, reducing energetic expenditures and the production of catabolites, preserving the cell structure and the fertilizing capacity of sperm. In contrast to a loss of quality (40-50%) occurs if compared to fresh semen, resulting from cooling processes freezing and thawing. These losses occur due to decreased sperm viability or damage to the functional capacity of the surviving sperm. Vitamin C is considered an antioxidant extracellular fluid, acting by preventing the formation of lipid hydroperoxide in plasma lipoproteins, and protecting the lipids in cell membranes while maintaining their structural integrity and viability during the cryopreservation process. Pentoxifylline is a methylxanthine derivative compound, the same class as caffeine and has the characteristic of inhibiting adenosine cyclic monophosphate (AMP) phosphodiesterase, causing an increase in the intracellular concentration of cyclic adenosine monophosphate (cAMP), activating the adenylyl cyclase which causes the activation of protein kinase-dependent and phosphorylation of sperm proteins, which are essential in initiation and maintenance of sperm movement. The objective of the experiment was to evaluate the use of vitamin C combined with pentoxifylline in the middle of cryopreservation of bovine semen that reduces the damage caused by oxidative stress and preserves sperm quality after thawing. It were used10 Nelore bulls with age / weight average of 31 months and 632kg, subjected to a semi-intensive system, raised on pasture Brachiaria brizanth cv, kept in sexual rest. One ejaculate was collected by electrical stimulation, which was analyzed after diluted in extender TRIS-citrate-yolk-glycerol (4%), divided into two parts: A part of the control (without additives) and the other supplemented with vitamin C (0.45 mg / ml) + pentoxifylline (1 mg / ml). Afterwards, the samples were cooled and frozen and stored until the time of analysis. After thawing, the samples were evaluated for motility and movement characteristics, plasma membrane integrity and acrosome, mitochondrial activity and level of lipid peroxidation (TBARS). The supplementation of cryopreservation did not alter (P> 0.05) the mitochondrial activity, acrosomal integrity, and concentration of spontaneous and induced TBARS. Based on the results it is concluded that the addition of vitamin C + pentoxifylline was not effective in reducing the damage caused by oxidative stress and cryopreservation of bovine semen samples.
Keywords: antioxidant, fertility, oxidative stress.