Avaliação da capacitação espermática in vitro pela viabilidade e reação acrossômica* Evaluation of in vitro sperm capacitation through viability and acrosome reaction

The aim of this study was to evaluate the "in vitro" sperm capacitation of bulls through the sperm viability and acrosome reaction. Semen of Gir bulls was incubated atO and 1 O J.tg/ml of heparin for four hours to capacitation. After then, lysophosphatidylcholine was added for 15 min., to induce acrosome reaction. The spermatozoa viability and acrosome reaction were determined at the beginning and at the end of incubation time by a semen sample on a glass microscope slide, stained with eosin/nigrosin and yellow naphtol/erthyrosin B, respectively. The heparin treatment showed the highest rate of spermatozoa with acrosome reactions (P<0,05), however it does no have effect on sperm viability. There was difference among bulls for spermatozoa viability and acrosome reactions before and after incubation time (P<0,05). The buli that showed the highest acrosome reaction showed the lowest spermatozoa viability. Since both variable are important for the fertilization, it must be evaluated "in vitro" sperm capacitation of bulls by the analyses of sperm viability and acrosome reaction rate together, due the difference observed between bulls.