Subtle method reduces animal suffering
A new method to test the toxicity of nonmutagenic chemicals reduces the suffering of experimental animals by reducing the exposure time required. Possibly the method can be improved so that animals can be dispensed with altogether. Testing new chemicals for toxicity is as difficult as it is necessary. While cell cultures provide the first indication of potential hazards, accurate testing often requires large numbers of test animals and experiments that are difficult to interpret. For chemicals that could be toxic but do not cause DNA damage (e.g. heavy metals), there are no well-suited genetically modified animal models. Therefore such substances are tested by exposing large numbers of animals to high doses over a long period of time.
Mario Sacco and his collaborators at the Institute of Advanced Biomedical Technologies at the National Research Council in Milan have developed a mouse model that makes these tests significantly easier (Nature Biotechnology, December 1997). The mice contain the genetic switch of the heat shock protein 70 (hsp70) gene. Hsp70 reacts to environmental stress such as heat, but also to damage caused by chemicals. The scientists connected the hsp70 switch to the gene for a human growth hormone. If the mouse cells detect damage, they produce the hormone, which can be easily detected in blood samples.
Since the hormone test is very sensitive, even small amounts of poison produce a measurable signal, which means that the tests can be carried out more quickly and with less stress for the animals. It is even possible to use the same mouse for several experiments, which can reduce the total number. In addition, the mouse cells can be cultured and provide a fairly reliable preliminary indication of the toxicity of the chemical.
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