Zona pellucida penetrability of metaphase I and II human oocytes after aging and salt treatment.

Human oocytes that failed to fertilize in vitro were examined for the degree of meiotic maturity and reinseminated either in the living state or after treatment with a concentrated salt solution as used for storage of human zonae pellucidae for diagnostic tests of sperm function. No dependence of zona pellucida penetrability on the oocyte maturity status was observed in either treatment group. Zonae pellucidae of metaphase I and metaphase II oocytes were equally penetrable after the salt treatment, whereas penetration occurred only exceptionally when the oocytes were living. These results show that, after in vitro aging and subsequent salt treatment, eventual differences in oocyte maturity status will not influence results of zona pellucida penetration tests. On the other hand, successful penetration of salt-stored zonae pellucidae by spermatozoa does not necessarily imply that these spermatozoa are able to penetrate the zona pellucida of a fresh living oocyte.