Validation of the hemizona assay in a monkey model: influence of oocyte maturational stages.

The hemizona assay (HZA) was used in the monkey model to investigate sperm binding to the zona pellucida and to evaluate binding patterns according to various stages of oocyte development. Adult cynomolgus monkeys were superovulated with human menopausal gonadotropin. The oocytes were retrieved by laparoscopy, stored in salt solution, then cut into hemizonae by micromanipulation. Metaphase II oocytes showed significantly tighter binding than prophase I oocytes (P less than 0.001). Metaphase I oocytes showed intermediate binding, significantly different from the other groups (P less than 0.01). It is concluded that: (1) This study demonstrates the feasibility of HZA as a test to evaluate sperm/zona interactions in the monkey, using standards reported for human studies. (2) Oocyte meiotic competence seems to be accompanied by an increase in zona-binding properties.