Does Progesterone Have A Role In Embryo-maternal Communication In Monodelphis Domestica?
Unlike eutherian mammals, marsupials generally exhibit no significant rise in serum during pregnancy. This observation has led to the conventional view that maternal recognition of pregnancy does not occur among marsupials. However, recent radioimmunoassay work with Monodelphis domestica reveals a slight increase in serum progesterone during the early stages of the 14-day pregnancy in this marsupial, peaking at day 3 and day 9. This elevation is consistent with specific nuclear staining of uterine-gland cells for progesterone receptor (PR), which occurs on days 3 to 9 of gestation. In addition, the PR-positive nuclei of uterine-gland cells during this period are situated near the basal lamina instead of their usual position at the center of each such cell. Consistent staining pattern of progesterone receptors in corpora lutea and ovarian follicles suggest minimal interaction between progesterone and involvement of the ovaries during gestation. However, the slight rise in serum progesterone, in combination with a significant increase in PR expression in the uterine-gland cells, suggests that progesterone signaling may play a heretofore under-appreciated role in marsupial pregnancy.