The Apparent Shift in Distribution of Aromatase Activity in the Subcellular Fraction of Human Term Placenta Stored At -96°C

The effects of storage at -96 degrees C on the distribution of the total aromatase activity in the homogenate, 900 xg pellet and 900 xg supernatant of two human term placentas were studied. Both specific and total aromatase activities in the 900 xg pellet increased through storage at -96 degrees C, while that in the 900 xg supernatant decreased. The ratio of total aromatase activity between the 900 xg pellet and 900 xg supernatant was about 2:1 in fresh placenta, but the ratio was about 19:1 in placenta stored at -96 degrees C for 3.5 months. Total aromatase activity in the tissue homogenate remained fairly constant throughout five months of storage at -96 degrees C. These data indicate that although active microsomal aromatase is thought to be available only from fresh placenta and the activity is lost quickly during storage of the tissue, aromatase itself is stable for months at -96 degrees C and the 900 xg pellet prepared from the frozen tissue contains almost the total original aromatase activity in the fresh placental tissue.