The persistence of the corpus luteum of pregnancy into lactation in the marsupial bandicoot, Isoodon macrourus

The bandicoot is unique among marsupials in possessing a corpus luteum of pregnancy which continues to secrete progesterone during lactation. Different factors which may influence the activity of this corpus luteum were examined. There was no correlation between the number of pouch young and the plasma progesterone concentration. Similarly, bromocryptine did not appear to cause a dramatic decrease in plasma progesterone early in lactation, however, it may induce premature regression of the corpus luteum late in lactation. Corpora lutea were not observed in the ovaries of two out of six bandicoots treated with bromocryptine late in lactation. Although the corpus luteum may influence ovarian activity early in lactation, and corpus luteum does not appear to influence reproduction late in lactation. Removal of corpora lutea at Day 30 of lactation caused an abrupt decline in plasma progesterone; however, the birth of the subsequent litter occurred on Days 58 and 61 (N = 2), births normally occurring on Day 60