[Regulation of aromatase in human choriocarcinoma cells]

To examine the mechanism regulating trophoblastic aromatase, we studied the effects of various agents on aromatase activity and the aromatase cytochrome P-450 (P-450arom) concentration in human choriocarcinoma JEG-3 cells. Aromatase activity was assessed by radioassay with [1 beta-3H] androstenedione. The P-450arom concentration was determined by an enzyme-linked immunosorbent assay with specific antibodies to P-450arom. Human chorionic gonadotropin (hCG) stimulated aromatase activity and increased the P-450arom concentration in a concentration-dependent (0.1-100 IU/ml) manner. Cholera toxin (CT), an adenylate cyclase activator, stimulated aromatase activity and the P-450arom concentration in a concentration-dependent (0.1-10ng/ml) and a time-dependent (12-72h) manner. 12-O-tetradecanoyl phorbol 13-acetate (TPA) (0.1-100ng/ml), a protein-kinase C activator, also stimulated aromatase activity and increased the P-450arom concentration. On the other hand, Ca2+ ionophore A23187, an agent increasing intracellular Ca2+ accumulation, inhibited aromatase activity and reduced the P-450arom concentration. The effects of CT, TPA and Ca2+ ionophore were additive. Aromatase activity was correlated with the P-450arom concentration. These results suggest that in JEG-3 cells the signal transduction system modulates aromatase activity by changing the P-450arom concentration.