SPERM BINDING-CAPACITY OF HUMAN ZONA-PELLUCIDA DERIVED FROM OOCYTES OBTAINED FROM DIFFERENT SOURCES

The important contributions of sperm-oocyte interaction to infertility diagnostics is well established. Scientists are urged to search for m ethods to improve the assessment of gamete interaction. Sperm binding and penetration assays have frequented the literature, reporting on va rious aspects of sperm-oocyte interaction using either microbisected o r whole human oocytes during the assay procedure. The objective of the study was to evaluate additional zona pellucida sources which can be used during zona binding studies. Hemizonae were obtained from the fol lowing oocytes: 1) experiment 1, prophase I oocytes from post-mortem o varian tissue from different age groups namely, 7 months, 5 years, 7 y ears, 12 years and 30 years; 2) experiment 2 used donated immature Pro phase I oocytes from the IVF treatment program and 3) experiment 3 eva luated zona binding for hemizonae which were previously used in hemizo na assays. Results indicated that, in experiment 1, ovarian age does n ot have any influence on the zona pellucida's capacity to bind spermat ozoa. The mean number of bound sperm among the different age groups di d not differ significantly, namely 38.9+/-17 (7 months), 31.0+/-27 (5 years), 49.3+/-21 (7 years), 32.8+/-18 (12 years) and 39.5+/-17 (30 ye ars). The pooled mean +/-SD binding for all the age groups in experime nt 1 was 37.7+/-7. Likewise, the mean number of sperm bound (experimen t 2) to zonae collected from oocytes using different ovulation inducti on regimes were 31.1+/-20 (unstimulated), 54.4+/-12 (HMG/HCG) and 15.3 +/-9 (HMG alone). The pooled binding data for experiment 2 were 33.0+/ -20. Results of experiment 3 indicated metaphase II oocytes with previ ous exposure to sperm retained its binding capacity indicating that he mizonae can be recycled for at least a second binding experiment. Zona e that had been exposed to sperm and that were subsequently stripped f rom bound sperm, revealed a mean number of bound sperm after re-insemi nation that were significantly higher than the prophase I oocytes name ly, 115.0+/-2.8 versus 35.6+/-12 (P=0.0001). In conclusion, the data h ighlights (i) new sources of human oocytes needed for sperm-oocyte int eraction studies; (ii) the capability of the human zona pellucida to b ind sperm after previous exposure and (iii) the importance of nuclear competence to obtain increased zona pellucida binding.