Peroxidase activity in the rat Zymbal gland and its possible role in the metabolic activation of aminostilbenes in the target tissue.

Peroxidase (EC 1.11.1.7) activity is detected in the rat Zymbal gland, which is the target organ of trans-4-dimethylaminostilbene (trans-DAS) carcinogenicity. Measurements of peroxidase activity in ovariectomized rats show that the enzyme activity is lowered in the uterus and Zymbal gland by trans-DAS treatment and in the lungs by diethylstilboestrol (DES) treatment. In an in vitro system containing horseradish peroxidase (HRP), hydrogen peroxide and calf-thymus DNA, irreversible binding of the 3H-labelled trans-DAS metabolites 3-hydroxy-, 4'-hydroxy-, and N-hydroxy-4-acetylaminostilbene to DNA is observed. The peroxidase activity in the Zymbal gland together with the HRP-catalyzed oxidation of trans-DAS metabolites suggest a possible role for peroxidase in the organ-specific metabolic activation of trans-DAS.