Genetic differences may occur in healthy animals, e.g. glomerular filtration rates vary
between inbred strains of rats (Hackbarth et al., 1981). Some strains such as diabetic rats
or the hyperlipidaemic Watanabe rabbit may be chosen specifically to test for toxic
effects of therapeutic agents, and the biochemical profiles of these strains will differ from
the strains used for general toxicology studies.