[Obtaining zona-free ova from the golden hamster (Mesocricetus auratus Waterhouse)]

Our methodology for obtaining zona-free ova from golden hamster females (Mesocricetus Auratus Waterhouse) is described here. Five groups of 5 females were superovulated injecting intraperitoneally pregnant mare gonadothropins (PMG) at different dosages. The control group received 0.25 ml of distilled water. We harvested 653 ova from the stimulated females with an average of 32.65 per individual (range 16-52). The control group produced a total of 50 ova with an average of 10 (range 0-14). PMG optimum dose was 25 IU with an average of 39 (S.D. +/- 10.93) (n = 195 ova). The best conditions for denuding the cumulus was a 0.01% hyaluronidase solution with an average time of 10 minutes (S.D. +/- 03'56"). The optimum conditions for digesting the zona was 0.20% trypsin during 03'20" (S.D. +/- 01'19"). The proof that the ova were not damaged by the procedure was by means of a supravital stain (Eosin Y). All mature ova (N = 681) were not affected by enzymes or manipulation. Final preparation used a 1% acetic acid fixation and staining with 0.01% methylene blue, both acting for 1-3 minutes. Animal gametes give us the opportunity to substitute human ova in biology of reproduction studies and experiments, avoiding technical, ethical and moral problems.