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Changes of androgen aromatase activity in the human placenta throughout pregnancy



Changes of androgen aromatase activity in the human placenta throughout pregnancy



Nichidai Igaku Zasshi 40(9): 941-948



Androgen aromatase in the human placenta represents an important enzyme for the synthesis of estrogen which increases with the progress of pregnancy. To evaluate the changes in androgen aromatase activity in human placentas throughout pregnancy, the in vitro androgen aromatase activity in homogenates, 900 .times. g pellets and 105,000 .times. g pellets prepared from fresh placentas from the 1st, 2nd and 3rd trimesters, was studied. The activity was measured by the 3H-water method after aerobic incubation of [1.beta.-3H, 4-14C]-androstenedione with samples in the presence of NADPH (600 .mu.M) and dithiothreitol (1 mM) in phosphate buffer (0.1 M, pH 7.5). The androgen aromatase specific activities in the homogenates, 900 .times. g pellets and 105,000 .times. g pellets from placentas in the 1st trimester were 50, 52 and 80 pmol estrogen/min per mg protein (mean), respectively. The activities of the 3 preparations from placentas of the 2nd and 3rd trimesters were similar to those found in the 1st trimester. The majority of the total androgen aromatase actvity from placentas of the 2nd and 3rd trimesters was sedimented in the 900 .times. g pellets (the total androgen aromatase activity in the 900 .times. g pellets was 3 times that in the 105,000 .times. g pellets). The total androgen aromatase activity in the placenta in the 3rd trimester was .apprx. 60 times that in the 1st trimester. The total androgen aromatase activity in the placenta apparently increases with the progress of pregnancy, while the androgen aromatase specific activity of each preparation is similar throughout pregnancy.

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Accession: 004916936

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