Abstract: The zona2f ree golden hamster oocytes were genet rated in vit ro by human spermatozoa. The hybrid zygotes were exposed to promutagen cyclophosphamide (CPA) at the concent rations of 20μg/ ml , 40μg/ ml ,60μg/ ml respectively during the peroid of post2fertilization culture. Then human sperm chromosomes were prepared and analyzed. The f requencies of the spermatozoa with st ructural aberrations were 33 % ,50 % ,33 % and the means of chromosomal breakages were 0. 54 ,1. 94 ,0. 72 successively in the above dose2groups. The differences of two parameters between the test groups and the cont rols were significant ( P < 0. 05 , P < 0.1) . The results indicated that the mutagenicity of the romutagens could be evaluated in human/ golden hamster hybrid zygotes as the endogenous metabolic activation system. This finding would be very beneficial for toxi2genetic research in mammalian gamates.

Key words: Zona-free hamster oocyte, Human sperm chromosome, Endogenous metabolic activation system, Cyclophosphamide