A consistently successful procedure for in vitro fertilization of golden hamster eggs

Complete details are described for the first time of the procedures used in the author's laboratory for obtaining in vitro fertilization (IVF) of golden hamster eggs leading to the first cleavage division. These IVF procedures have been developed during the past 20 years and are very reproducible: IVF of at least 75% of eggs is routinely achieved, and on average 65% of inseminated eggs undergo the first cleavage division in vitro. These results can easily be obtained by inexperienced investigators. The ease and reproducibility of the hamster IVF procedures make them very suitable for studies of sperm:egg interaction and associated events. Studies in the author's laboratory have included analysis of sperm fertilizing ability under chemically defined conditions, the presence of sperm acrosome reaction stimulating factors in the egg investments, maturation of oocytes in vitro, the block to polyspermy, and the contribution of egg aging to fertilization anomalies. In addition, the motility of hamster sperm under chemically defined conditions is used in a routine screening protocol for detecting contaminants in the culture milieu. Golden hamster gametes offer several distinct advantages for IVF studies, including the large size of the sperm acrosome, the persistence of the very large sperm tail in the ooplasm for many hours following fertilization, and the translucence of the ooplasm, which facilitates observation of the sperm tail and pronuclei. The female golden hamster exhibits a regular 4 day estrous cycle, with distinctive indications of estrus and proestrus phases. Because of the advantages of using the golden hamster, the procedures described in this report may be useful to other investigators wishing to conduct research using IVF. Essentially the same IVF procedures can be used with monkey and bovine gametes.