Fig. 3. The ligand in the peripheral fraction of the ovulated zona pellucida (ZP) is not a contaminant of the cortical granules. (A) N-acetylglucosaminidase activity of fractions of the ovulated ZP (three ZP equivalents/µl) prepared from eggs treated with 10 µM A23187 to induce the cortical reaction or DMSO, as control. (B) Biological activity of the ovulated ZP fractions (three ZP equivalents/µl) prior to and after treatment of the eggs with 10 µM A23187. Each bar represents the mean±s.d.; n=2 experiments. In a single experiment, the value for each data point represents the average of three determinations (for a total of six assays per data point). The peripheral fraction contains variable amounts of GlcNAc'ase, but this contribution does not account for its biological activity.