Recently, it has also been reported that in some mammals, the formation of the CG envelope, after CG exocytosis, in the perivitelline space (PVS) also plays an important role in the block to polyspermy. According to the study by Cran and Cheng in pig oocytes, the formation of the CG envelope may in fact represent the dispersion of CG exudates. Wells et al. reported that A23187 treatment of pig oocytes prevented sperm penetration if insemination was conducted soon after treatment, but this block disappeared if oocytes were cultured for > 2 h before insemination. Our present study (experiment 2) gave different results from those reported by Wells et al.. We found that even when the treated oocytes were cultured for 3.5 h before insemination, the oocytes still possessed the ability to resist sperm penetration. The differences between the two studies may be due to different media or to different supplementations. Although there was no information about the medium used in the study by Wells et al. buy asthma inhaler
Our unpublished data indicated that if oocytes were treated with A23187 in TCM-199 plus 10% fetal calf serum (FCS; a widely used medium for pig IVF) or in mTBM plus 10% FCS (unpublished data) and then inseminated in the same medium, sperm penetration was not prevented even though CG exocytosis had occurred in the treated oocytes.