Abstract: The development of multicellular animals depends on cell-cell communication,and one of the mediators for the communication is cytokines.After fertilization,the development of mammalian early embryos during transition from maternal to zygotic genetic control requires the stimulation of external signal excreted from oviduct epithelial cells (OEC),otherwise,the developmental block occurs.We studied on the characterization and biological function of rabbit oviductal epithelial cells proteins (ROPs).There are three sets of ROPs with molecular weight of ROPs ranging from 44 kD to 135 kD,and their isoelectric points ranged from 4.5 to 5.9.Two sets of them were determined to be acid glycoproteins by treatment of WGA lectin sepharose and analysis of 2-D SDS-PAGE.After digestion with N- and O-glycosidase,the third set of the glycoproteins were degraded to become two or three spots with molecular weight about 30 kD or less,and their isoelectric points changed to about 5.5 and 5.6.Furthermore,the function of ROPs was analysed by using polyclonal antibody and antiserum against total ROPs (Arop-T) and against different molecular weight of ROP (Arop-Ⅰ,-Ⅱ and -Ⅲ).Arop-T and Arop-Ⅰ respectively completely arrest the development of mouse early embryos,and Arop-Ⅱ blocked the development of 75% mouse embryos,but Arop-Ⅲ almost cannot significantly arrest their preimplantation development.Immunoblotting analysis indicated that Arop-T and Arop-Ⅰ positively reacted on both ROP-68 and ROP-55,and that Arop-Ⅱ only positively reacted on ROP-68.The data conincide with our previous result of 125Ⅰ-labelling ROPs in the zona pellucida of embryos.These results suggested that ROP-68 and ROP-55 were the oviductal cytokine inducing initiation of zygotic gene and realizing normal transition of maternal to zygotic control of early embryo development.