Efeito da adição de um quelante de cálcio sobre a qualidade do sêmen descongelado de cães

• Autor(a) principal: Souza, Thyara de Deco
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1462
• topic: EDTA; Capacitação; Criopreservação espermática; EDTA; Capacitation; Sperm cryopreservation; CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA

We aim to evaluate the effect of reducing the free calcium in the freezing medium, using a calcium chelating agent (EDTA) at concentrations of 0.3% and 0.5%, on the quality of frozen-thawed dog sperm. The sperm-rich fractions from three mixed breed dogs was collected by penile stimulation and evaluated for sperm progressive status, sperm motility, sperm morphology and hypoosmotic swelling test (HOST). Thereafter, it was divided into three aliquots, which were diluted in a Tris-based extender to reach a final concentration of 50 x 106 motile spermatozoa / mL, 6% glycerol and 0.5% Equex STM Paste® (TGE), or in the same extender with the addition of EDTA to a final concentration of 0.3% (EDTA0.3) or to a final concentration of 0.5% (EDTA0.5). After packaged in 0.25 ml straws each treatment was cooled for two hours and frozen in nitrogen vapor for 15 minutes. The samples were thawed by immersion in water bath at 37 °C for 7 seconds and evaluated as the fresh semen and for the thermoresistance test, the sperm- (MPOG) binding assay and for the integrity of the sperm plasma and acrosome membrane, using fluorescent probes. The calcium concentration as measured, using a spectrophotometer, in diluted fresh semen and in frozen-thawed semen. There was reduction (Duncan at 5% of significance; p <0.05) in calcium concentration in both treatments EDTA0.3 and EDTA0.5 but only when EDTA was added to a final concentration of 0.5% all the free calcium present in the medium was removed. According to the fluorescent probes the reduction or the elimination of free calcium in the medium was not able to reduce the amount of frozen-thawed sperm with damaged / reacted acrosome (p> 0.05) compared to group TGE, with 10.8 % to 14% of sperm showing both membranes intact. There was also no difference in the number of spermatozoa bound to MOPG in the group TGE and EDTA0.3 and EDTA0.5 treatments. Although there was no difference (p> 0.05) in sperm motility between the TGE group (74.70%) and EDTA0.3 (62.78%) treated group, this parameter decreased (p <0.05) in EDTA0.5 treatment (45%), emphasizing the importance of calcium for sperm motility. Therefore the reduction or elimination of free calcium in the freezing medium able to reduce the premature cryocapacitaion and acrosome reaction, which would improve sperm quality after thawing. Thus there are other factors in the medium and / or processing used that are triggering injury and favoring the incidence of premature capacitation and AR in sperm.