A comparison of proteins synthesized and secreted by peri-implantation embryos of rats and mice
MetadataShow full item record
Psychoyos (1973) has defined embryo implantation in rodents as the result of coordinated interactions between a uterus that is "receptive" and an embryo that has reached the "blastocyst stage" of development. In rats and mice, uterine "receptivity" is vaguely understood as the ability of the endometrium to undergo decidualization and formation of the maternal plancenta; it is achieved only after exposure to ovarian hormones secreted in a specific sequence (Psychoyos 1976) . The process of decidualization involves profound changes in both morphological and biocherical characteristics of the endometrial stroma including a localized increase in vascular permeability and tissue edema, increased rates of cell proliferation, differentiation of stromal cells into so-called "decidual cells," and increases in synthesis of DNA, RNA and protein (De Feo 1967 and Finn 1977). Because decidualization only occurs in areas adjacent to the blastocysts and can be observed even before their attachment to the uterus, it is believed that a soluble factor from the embryo must exist which acts as a signal to trigger the reaction. Although the nature of the soluble factor has not been determined, it has been proposed at one time or another that steroids, histamine, prostaglandins or proteins from the embryos are responsible (see Kennedy 1983; Weitlauf 1988, for reviews).