Suicide inactivation of androstenedione aromatase in human placenta by fluoroethindrone (10 beta-fluoro-17 alpha-ethynyl-19-nortestosterone).

: The inhibitory effects of androstenedione aromatase activity in human placenta using fluoroethindrone (10 beta-fluoro-17 alpha-ethynyl-19-nortestosterone), which is a derivative of norethindrone (17 alpha-ethynyl-19-nortestosterone, ENT) and, unlike ENT, is considered to be refractory to aromatization, was investigated in this study. When fluoroethindrone was added to the placental microsomes in the presence of NADPH, androstenedione aromatase activity in the placental microsomes was decreased time dependently and dose-dependently by fluoroethindrone compared with the samples without NADPH. This finding suggests that fluoroethindrone acts as a suicide substrate for androstenedione aromatase in human placenta.