Pig sperm preincubation and gamete coincubation with glutamate enhance sperm-oocyte binding and in vitro fertilization

Abstract As the taste receptor for monosodium glutamate (umami) is expressed in both murine and human spermatozoa and the presence of α-gustducin and α-transducin, G proteins involved in the umami taste signaling, has been described in boar germ cells, the aim of this study was to evaluate if monosodium glutamate (MSG) would exert any effect on sperm-oocyte binding, in vitro fertilization (IVF) and sperm parameters during in vitro induced capacitation. For sperm-zona pellucida binding assay, boar spermatozoa were preincubated for 1 h and then coincubated for 1 h with denuded in vitro matured oocytes in presence of different concentrations of MSG (0, 0.1, 1, 10 mM). MSG 1 and 10 mM significantly (P  For in vitro fertilization trials, both sperm preicubation (1 h) and gamete coincubation (1 h) were performed in presence of different concentrations of MSG (0, 0.1, 1, 10 mM). After 19 h of culture in fresh IVF medium, oocytes were fixed. MSG 1 mM significantly (P  The addition of MSG during in vitro induced capacitation of boar spermatozoa did not cause any significant difference, compared with control, on the percentage of viable cells, spermatozoa with intact acrosome and the percentage of spermatozoa displaying tyrosine - phosphorylation of sperm tail proteins. In order to evaluate whether the effect elicited by MSG could be due to glutamate uptake in boar spermatozoa, fertilization trials were performed in presence of either 1 mM MSG or 1 mM MSG + 100 μM DL- threo -beta-hydroxyaspartic acid (THA), a non selective inhibitor of glutamate uptake. A significant increase (P  Our study demonstrates for the first time that glutamate exerts a positive effect on sperm-oocyte binding and fertilization. Further studies are needed to clarify the mechanism by which glutamate exert his effect.