Document Type : Original Article
CLINICAL SCIENCES DEPARTMENT, VET MED FACULTY, SHAHR-E-KORD UNIVERSITY
Introduction: Standard concentrations of antibiotics in culture media are thought to have no detectable toxic effects on the cultured cells. However, 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 penicllin-streptomycin (pen-strep) during in vitro maturation (IVM) of bovine cumulus oocyte complexes (COCs) affect nuclear and cytoplasmic maturation and subsequent embryo development.
Materials and Methods: Bovine COCs were matured at 39oC in a humidified atmosphere with 5 % CO2 in air for 24 h in: 1- culture medium M 199 supplemented with 10 % FCS (Fetal calf serum), 0.05 IU/ml rhFSH (recombinant human FSH) and 100 units penicillin and 100 ?g streptomycin/ ml. 2- culture medium M 199 without FCS and rhFSH in the presence of pen-strep. Cultures without antibiotics served as control. Six series of experiments, each consisted of at least 3 replicates, were performed.
Results: In vitro maturation 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 appearance of the cumulus investment, into bright and dark groups, this effect was less obvious in both types of COCs, 76% vs 72% in bright COCs (P= 0.149) or 83% vs 80% in dark COCs (P=0.296) in treated and control groups respectively. The percentage of oocytes with type III of cortical granules (CGs) distribution was not affected in the presence of pen-strep. The COCs expansion after IVM was not affected by the presence of antibiotics in culture medium. The subsequent embryo development of IVM/IVF produced ova, which were exposed to pen-strep during IVM, was significantly (P<0.05) decreased with respect to blastocyst formation by day 9. In vitro maturation in the presence of pen-strep in culture medium without FCS and rhFSH had no significant (P=0.402) effect on nuclear maturation.
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.