Title: Analysis of the factor(s) present in follicular fluids promoting male pronucleus formation ability of porcine follicular oocytes.
Abstract: Follicular fluids (FFs) were collected from porcine or bovine medium-sized (25 mm in diameter), porcine large-sized (5 mm<) and bovine large-sized (1020 mm) follicles (pMFF, bMFF, pLFF and bLFF respectively), and their effect on male pronucleus (mPN) formation was examined after in vitro fertilization of porcine follicular oocytes matured in the presence of these FFs. All FFs dose-dependently elevated the mPN formed oocytes from 1628% to more than 75% of penetrated oocytes. The inclinations of the regression lines were not different between any two FFs, suggesting that the effective factor(s) will be essentially the same between pig and cattle. The concentrations in MFFs were about three times higher than LFFs and those in bFFs were about two times higher than pFFs. Heating of pMFF at 56°C for 30min did not deteriorate its efficiency. High molecular weight components (12, 000<) of pMFF improved mPN formation rate (64.9%), but low molecular weight components (25, 000>) were not effective (the rate was 10.0%). These results suggest that the effective factor(s) will be present widely in many species and might function physiologically. The examined characteristics of the factor (s) are compatible with glucosaminoglicans and inhibin.