In vitro inhibition of aromatase by the enantiomers of aminoglutethimide and analogs

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Abstract
The in vitro aromatase activity in microsomal fractions from rat ovary and its inhibition by enantiomers of aminoglutethimide (AG), rogletimide (RG), and cyclohexylaminoglutethimide (ChAG) were studied by analysing the [3H]H2O released when [1β‐3H]androstenedione was converted to estrone. Maximum velocity (Vmax) and the Michaelis‐Menten constant (Km) of the microsomal aromatase enzyme were 17.40 ± 0.45 pmol/ml/mg protein/min and 1.02 ± 0.06 μM, respectively. The IC50s for the enantiomers were similar for (+)‐R‐AG and (−)‐R‐ChAG (0.86 ± 0.06 and 0.89 ± 0.15 μM, respectively). (+)S‐ChA'G was most potent with IC50 of 0.075 ± 0.003 μM. The IC50s for (−)‐S‐AG, (+)‐R‐RG, and (−)‐S‐RG were in the same range (23.15 ± 2.74, 24.58 ± 2.46, and 24.43 ± 2.20 μM, respectively).