Hamsters and Gerbils: Advantages and Disadvantages as Models in Toxicity Testing

Abstract

The need for additional species of laboratory animals for toxicity testing, especially for chronic (lifetime) carcinogenesis bioassay, becomes more apparent as data on such tests in mice and rats accumulate and undergo analysis. The results of approximately half of the lifetime carcinogenesis bioassays conducted by the National Cancer Institute and the National Toxicology Program were either equivocal or unevaluable. Some changes must, therefore, be considered for carcinogenesis bioassay guidelines, and foremost among such improvements would be the inclusion of a species with few spontaneous tumors, healthy parenchymal organs (especially liver), and proven susceptibility to administered standard carcinogens and other substances known to be carcinogenic to man or other laboratory animals. Mesocricetus auratus, the Syrian golden hamster, is such a species. A considerable body of background information on Syrian hamsters is available and continues to accumulate in the literature. Information on gerbils (Meriones unguiculatus) is less voluminous, but that which is known suggests that this species as well could contribute toward improvement in toxicological and carcinogenesis bioassays. There are some limitations, however, which apply to gerbils, namely, a much longer lifespan than most other laboratory rodents, fairly high frequency of spontaneous tumors, and great diversity in the nature of such naturally occurring tumors. Gerbil population genetics has been studied less thoroughly. Inbred Syrian hamsters and their genetically defined hybrids, standardized for carcinogenesis responsiveness, healthy and long-lived, are now readily available, making it possible to reproduce results at any time in different laboratories.