Species and sex differences in the liver microsomal nitroreductive biotransformation of nifurtimox and benznidazole

Abstract

Nifurtimox (NFX) and Benznidazole (Bz) are two drugs effective against acute Chagas' disease. Both have considerable toxic side effects related to nitroreductive biotransformation. In this work, we studied the species and sex differences in liver microsomal NFX (NFX-ase) and Bz nitroreductase activity (Bz-ase). Animal species tested were rats, mice, hamsters and guinea-pigs. Bz-ase is significantly higher in male rats and hamsters than in females. No significant sex difference was observed in mice or guinea-pigs. Bz-ase in the males is: hamsters greater than mice greater than guinea-pig approximately equal to rat and in females it is: mice approximately equal to guinea-pig approximately equal to hamster greater than rat. NFX-ase is higher in either male rats or female mice than in either female rats or male mice. No sex difference was observed in the other species. In males NFX-ase is: hamsters approximately equal to mice greater than rat approximately equal to guinea-pig, while in females it is mice approximately equal to hamsters greater than guinea-pig approximately equal to rat. Results suggest that hamsters and mice might be the most suitable species to study toxic effects related to their liver microsomal nitroreductive biotransformation. This might be of particular relevance for carcinogenicity studies.