Oocyte and zygote zona pellucida permeability to macromolecules

Zona pellucida intact mouse pre- and post-ovulatory oocytes and zygotes were investigated for permeability to macromolecules using graded neutral fluorescein isothiocyanate (FITC) dextrans (molecular weight range 3.84-170 kDa) and a range of galactose-binding lectins (molecular weight range 40-247 kDa). The use of both FITC neutral dextrans and FITC galactose-binding lectins gave good agreement in the zona pellucida permeability studies. Zona pellucida intact pre- and post-ovulatory oocytes were permeable to both markers up to a molecular weight range of 170 kDa although movement across the zona pellucida was diminished between 100 to 150 kDa with no detectable permeability at molecular weight range of 170 kDa. Zygotes demonstrated a decreased zona pellucida permeability at around 110 kDa. Two galactose-containing oligosaccharide-rich zones in the zona pellucida were identified, and changes in zygote vitelline membrane galactose-binding lectin affinity were detected.