PROSTAGLANDIN SYNTHASE AND HORSERADISH-PEROXIDASE CATALYZED DNA-BINDING OF PARA-PHENETIDINE

The prostaglandin synthase and horseradish peroxidase catalyzed binding of p-phenetidine to DNA was investigated. The addition of arachidonic acid to an incubation containing ram seminal vesicle microsomes, [14C]p-phenetidine and DNA resulted in a rapid incorporation of radioactivity into DNA. This was inhibited by > 75% by indomethacin (0.1 mM) or butylated hydroxyanisole (0.5 mM). H2O2 was as efficient as arachidonic acid in mediating the activation of p-phenetidine thus implicating the involvement of the hydroperoxidase activity of prostaglandin synthase in this reaction. Horseradish peroxidase and H2O2 also catalyzed the activation of p-phenetidine to DNA-binding metabolites. Reduced glutathione (GSH) stimulated the binding of p-phenetidine to DNA by > 3-fold by in both the prostaglandin synthase and the horseradish peroxidase system, whereas cysteine and N-acetylcysteine reduced the DNA-binding in the prostaglandin synthase system by up to 62% under the conditions used. Water-soluble metabolites formed in the presence of GSH also bound to DNA. A 72-h dialysis of DNA samples from incubations with GSH present reduced the amount of bound material by 75%. The radioactivity which associated with DNA in the absence of GSH was not decreased by dialysis.