ABSTRACT

The species variation in target organ toxicity exhibited by chemicals may be divided into broad categories. The most widely used species for toxicity testing are mice, rats, and dogs, although pigs and nonhuman primates may also be employed. Rats and mice are generally used for carcinogenicity testing. The identification of species differences in target organ susceptibility or specificity may lead to the production of agents capable of selectively destroying organisms for health or economic reasons. Many toxins must be metabolically activated in order to express their toxicity. The selective rat toxicant norbormide causes irreversible constriction of vascular smooth muscle, leading to ischemia and death. Qualitative and quantitative variations in the biotransformation of chemicals have been much studied and are well established as a cause of species differences in their toxicity.