Relationship between the covalent binding of N-acetoxy-2-acetylaminofluorene to DNA and a steroidal esterase activity in human mononuclear leukocytes

Abstract A method for the quantitative assessment of steroidal esterase activity in viable human mononuclear leukocytes (HML) has been developed. It is based on estimating the conversion of [ 3 H]beclomethasone-17,21-dipropionate (BDP) to beclomethasone-17-monopropionate (BMP) using TLC on silica gel 60 F-254 plates developed in a solvent system of chloroform/methanol (97:3, v/v). The cell assay procedure was dependent on BDP concentration, incubation time and cell concentration. The steroidal esterase activity was competed for by N -acetoxy- N -acetyl-2-aminofluorene (NA-AAF) and completely inhibited by 100 μM paraoxon. When [ 3 H]NA-AAF binding to DNA was used as an indicator of HML esterase (deacylase) activity, BDP functioned as a substrate inhibitor. Parallel estimations of BDP metabolism and NA-AAF binding to DNA indicated striking correlations in the interindividual variations ( r = 0.62, P