penicillin-streptomycin in the culture medium during in vitro maturation of bovine oocytes affects nuclear maturation and subsequent embryo development

introduction: standard concentrations of antibiotics in culture media are thought to have no detectable toxic effects on the cultured cells. since antibiotics are biologically active substances, the possibility that they interfere to some extent with cellular processes occurring in the cultured cells can not always be totally excluded. this study, therefore, was conducted to assess whether the presence of penicillin-streptomycin (pen-strep) during the ivm (in vitro maturation) of bovine cocs (cumulus oocyte complexes) affect nuclear and cytoplasmic maturation and subsequent embryo development. materials and methods: bovine cocs were cultured at 39oc in a humidified atmosphere with 5 % co2 in air for 24 h in: 1- m199 supplemented with 10 % fcs, 0.05 iu/ml rhfsh and 100 units penicillin and 100 µg streptomycin/ ml. 2- m199 without fcs and rhfsh in the presence of pen-strep. cultures without antibiotics served as control. results: in vitro maturation of bovine cocs in the presence of pen-strep in culture medium supplemented with fcs and rhfsh significantly (p< 0.05) increased the percentage of mii oocytes. however, when the cocs were divided, on the basis of apperance of the cumulus investment, into bright and dark groups, the positive effect of pen-strep on nuclear maturation became less obvious in both types of cocs, 76% vs 72% in bright cocs (p= 0.149) and 83% vs 80% in dark cocs (p= 0.296) in treated and control groups, respectively. moreover, when fcs and rhfsh were excluded from culture medium the positive effect of pen-strep on nuclear maturation (p= 0.402) was omitted. the percentage of oocytes with type iii of cortical granules (cgs) distribution and the cocs expansion was not affected by the presence of pen-strep during ivm. the subsequent embryo development of ivm/ivf produced ova, wich were exposed to pen-strep during ivm, was significantly (p<0.05) decreased with respect to the blastocyst formation by day 9. conclusion: the results indicate that the nuclear maturation of bovine oocytes was positively influenced by the presence of pen-strep during ivm when the culture media was supplemented with fcs and rhfsh. moreover, despite of no notable effect of pen-strep on cgs distribution the subsequent embryo development was negatively influenced by the presence of pen-strep.