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Peroxidase Metabolism of the Urinary Bladder Carcinogen 2-Amino-4-(5-nitro-2-furyl)thiazole¹

Geriatric Research, Education, and Clinical Center, Veterans Administration Medical Center, St. Louis, Missouri 63125 [T. V. Z., B. B. D.], and Departments of Biochemistry [R. W. W., T. V. Z.] and Internal Medicine [T. V. Z., B. B. D.], St. Louis, University School of Medicine, St. Louis, Missouri 63106

Metabolism of 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT) by a variety of different peroxidases was examined. Metabolism of ANFT was measured by the binding of radiolabeled substrates to protein and DNA. Prostaglandin hydroperoxidase but not horseradish peroxidase, lactoperoxidase, or chloroperoxidase metabolically activated ANFT. All four peroxidases catalyzed the binding of benzidine to protein and DNA. With peroxide substrates, peroxidase-catalyzed binding of both carcinogens was observed with or without molecular oxygen. Arachidonic acid-dependent binding of ANFT and benzidine by prostaglandin endoperoxide synthetase was inhibited by anaerobic conditions and aspirin. Chloroperoxidase activation of benzidine was also inhibited by aspirin. Vitamin Einhibited activation of both carcinogens by all enzymes examined. Prostaglandin hydroperoxidasecatalyzed binding of benzidine to protein was inhibited by the 5-nitrofurans ANFT and 3-hydroxymethyl-1-{[3-(5-nitro-2-furyl)allydidene]amino}hydantoin and acetaminophen, while only acetaminophen inhibited horseradish peroxidase-catalyzed binding. These results indicate that different peroxidases may exhibit specificity with respect to their activation of carcinogens. Only prostaglandin hydroperoxidase activated the 5-nitrofuran ANFT, while a number of peroxidases activated the aromatic amine benzidine.

¹ This work was supported by the Veterans Administration and by the USPHS Grant CA-28015 from the National Cancer Institute through the National Bladder Cancer Project.

² To whom requests for reprints should be addressed, at Geriatric Center (111G-JB), Veterans Administration Medical Center, St. Louis, Mo. 63125.

Received 4/ 1/82. Accepted 12/30/82.