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.
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