Uso da L-arginina nos processos de capacitação espermática e fecundação in vitro de oócitos bovinos

Abstract

The aim of this work was to evaluate the use of the L-arginine in sperm capacitation and in vitro fertilization (IVF), analyzing its influence on the embryonic development, using semen from two bulls (Bos taurus and Bos indicus). In experiment 1, the spermatozoa had been incubated without oocytes, during 0, 1, 2 and 3 hour in IVF medium added of 0, 1, 10 and 50 mM L-arginine. In experiment 2, spermatozoa and oocytes had been incubated in IVF medium added with the L-arginine concentrations previously cited, during approximately 30 hour. The bovine oocytes had been matured in vitro (IVM) and embryonic culture (IVC) was supported by a monolayer of granulosa cells in SOF medium. It was evaluated fertilization (18 hpi), clivage and blastocyst rates (2º and 7º culture day, respectively). The Griess colorimetric method was applied to mensurement of the NO3 -/NO2 - produced during the IVF. For statistics analysis, values were considered significantly different if P<0.05 following the ANOVA test. The results had shown that L-arginine (1 mM), when added during sperm capacitation for two hours, increased the acrosome reaction rate as compared to Bos taurus control group (31,1±2,78 versus 23,4±2,65). The addition of L-arginine (50 mM) to IVF medium (experiment 2), in both Bos taurus and Bos indicus spermatozoa, decreased clivage rate (78,7±2,17 versus 65,7±9,32; 72,7±3,36 versus 45±7,12; respectively) and blastocyst rate (39,4±3,78 versus 15,2±6,12; 39,4±4,39 versus 16±8,54; respectively) as compared to control group. These results provide that L-arginine increased the acrosome reaction rate in Bos taurus, however reduced the clivage and blastocyst rates in both the bulls, but had not influenced the embryo quality.