Uterine morphology and the distribution of granulated metrial gland cells in the virgin and pregnant short-tailed field vole, Microtus agrestis.

The morphology of the uterine wall in the virgin pregnant and postpartum short-tailed field vole (Microtus agrestis) was studied with particular reference to the distribution of granulated metrial gland (GMG) cells. In comparison with the mouse, the changes which occur in the uterine wall during pregnancy and into the postpartum period are broadly similar. However, unlike in the mouse, GMG cells were a feature of the uterine wall in virgin mice and of the antimesometrial decidua in pregnancy. In pregnancy, GMG cells were not found in the lumina of blood vessels in the uterine wall or in the maternal blood spaces of the fetal placenta. During early pregnancy, giant interstitial trophoblast cells invade the decidualising endometrium. No association was found between uterine leucocytes, including GMG cells, and interstitial trophoblast cells, indicating that the trophoblast invasion is not influenced by leucocytes.