Avoidance of used endometrial sites by blastocysts of the bank vole, Clethrionomys glareolus

Abstract

In bank voles blastocysts arising from mating immediately after parturition do not implant in used zones of the preceding pregnancy but in the regions between them. However, if mating is postponed until 12 or more days after parturition blastocysts do implant in used zones of the previous pregnancy. Implantations also occur at zones used two pregnancies previously. It seems likely that the absence of implantations at recently used zones of the uterus is determined by the uterus rather than blastocysts.

Distribution of macrophages in the mouse uterus from one day to three months after parturition, as defined by the immunohistochemical localization of the macrophage‐restricted antigens F4/80 and macrosialin

“…Implantations do not occur in the immediate vicinity of nodules in the mouse (unpublished observations), rat (Momberg and Conaway, 1956), hamster (Orsini, 19621, and bank vole (Nerquaye-Tetteh and Clarke, 1990) suggesting that these structures exert some influence over the endometrium in their vicinity. Differences in the experimentally induced decidual reaction have been observed in the vicinity of nodules in the mouse (Brandon, 1990) and bank vole (Nerquaye-Tetteh and Clarke, 1990). Since nodules are found in the mesometrial uterus and implantation, and decidualization, are initiated antimesometrially in the rodent uterus, the influence of nodules must extend several millimeters from their location.…”

“…Implantations of the first pregnancy can occur anywhere along the length of the rodent uterus but implants of second and subsequent pregnancies do not occur in the vicinity of the post-partum nodules derived from previous pregnancies (Deno, 1937;Momberg and Conaway, 1956;Orsini, 1962;Nerquaye-Tetteh and Clarke, 1990). These nodules form at the base of the mesometrial membrane above the site of placental detachment and are found in the uteri of many rodents (see Deno, 1937).…”