Chlortetracycline fluorescence patterns and in vitro fertilisation of frozen-thawed boar spermatozoa incubated under various bicarbonate concentrations.

Porcine oocyte-cumulus complexes were cultured in bovine serum albumin(BSA)-free North Carolina State University (NCSU)23 medium containing porcine follicular fluid (10%), cysteine (0.1 mg/ml)and hormonal supplements (eCG and hCG: 10IU/ml each) for 22h. They were then cultured in the same medium but without hormonal supplements for an additional 22h. After culture, cumulus cells were removed and oocytes were co-incubated with frozen-thawed ejaculated boar spermatozoa in tissue culture medium (TCM)199 containing caffeine (5mM), fetal calf serum (FCS; 10%) and varying concentrations (26–56 mM)of NaHCO 3 for 9h(experiment 1). In experiment 2, chlortetracycline (CTC) was used to assess the functional state of spermatozoa incubated under different NaHCO 3 concentrations. Experiment 3 examined the effect of FCS (1% and 10%)and NaHCO 3 (26 and 46 mM) on fertilisation parameters. Compared with 26 mM, penetration rate was significantly higher ( p 3 . Polyspermy showed a similar pattern although no difference was observed between 26 and 36 mM. At 46mM NaHCO 3 , the mean number of spermatozoa (MNS) penetrated per oocyte increased significantly ( p 3 , respectively. The fertilisation medium containing 46mM NaHCO 3 and 1% FCS showed a higher penetration rate (84%)with a relatively low incidence of polyspermy (39%). The results indicate that NaHCO 3 stimulates capacitation and/or the acrosome reaction of boar spermatozoa in a dose-dependent manner and thus affects fertilisation parameters.