Fertilization in vitro of Rabbit Eggs by Epididymal Spermatozoa Capacitated in a Chemically Defined Medium

Abstract

Newly ovulated eggs from mature does treated with follicle stimulating hormone and hCG [human chorionic gonadotropin] were inseminated in a defined medium with epididymal spermatozoa which were treated with the standard or HIS [high ionic strength] medium for 15 min and preincubated for 10-10.5 h in a CO2 incubator. When spermatozoa in which viability after preincubation was maintained at levels of 50-60% were used, sperm penetration through the zona pellucida started 1-1.25 h after insemination and the transformation of sperm head into the male pronucleus occurred within 2 h in spermatozoa treated either with the standard or with HIS media. There was no significant difference between the overall penetration rates of the eggs 1-5.25 h after insemination with the spermatozoa treated with the standard (68.3%) or HIS media (59.1%). Most of the penetrated eggs developed to 2- or 4-cell and 8- to 16-cell stages 24 and 48 h after insemination, respectively. When 4 denuded eggs were inseminated with spermatozoa preincubated after treatment with the standard medium, all of them were penetrated with male pronucleus 5 h later. In some bucks, the proportion of motile spermatozoa after preincubation was greatly decreased (less than 5%), and such spermatozoa showed very low penetration ability.