Progesterone concentration in rabbit uterine flushings before implantation

Abstract

The concentration of progesterone in non-pregnant and pregnant rabbit uterine flushings and plasma was measured. Pregnancy was associated with increased progesterone, total protein and uteroglobin concentrations in uterine flushings 4-6 days after mating, the progesterone increase being the most rapid. By using a MW of 15,000 for uteroglobin (Murray, McGaughy and Yarus, 1972), a ratio of 1 molecule of progesterone to 3000-4000 molecules of uteroglobin on days 4 and 5 post coitum was calculated. On day 6 there is about 1 molecule of progesterone to 400 molecules of uteroglobin. The reason for this abrupt change is unknown, and the precise role that progesterone in the rabbit uterine secretions plays in implantation and early embryonic development needs to be investigated further.