Effects of progesterone and estradiol on aminopeptidase A (AAP) and leucine aminopeptidase (LAP) activities in the pregnancy serum and placenta of the rat.

We investigated the effects of estradiol and progesterone on placental aminopeptidase A and leucine aminopeptidase activities in pregnant rats. Estradiol (0.5, 1.0 and 2 mg/day) plus progesterone (5, 10 and 20 mg/day) was given for five days starting from the 16th day. Changes in both enzyme activities in the serum, placental cytosol and microsome caused by the steroids were analyzed. Aminopeptidase A activities in all three compartments and leucine aminopeptidase activities in the serum and cytosol were stimulated by estradiol (1.0 mg/day) plus progesterone (10 mg/day). Since we previously found that the placental aminopeptidases degrade peptide hormones, our present study suggests that steroids effect the metabolism of peptide hormones of fetal and/or maternal origin.