Metallothionein-I transgenic mice are not protected from gamma-radiation

Metallothionein (MT) has been proposed to play a protective role against the toxic effects of free radicals and electrophiles, such as those produced by gamma-radiation. Therefore, this study was designed to determine whether MT-transgenic mice, which carry 56 copies of the MT-I transgene and have higher tissue MT concentrations, are resistant to the toxic effects of gamma-radiation. Mice were exposed to 137cesium radiation, and survival was followed for 30 days. At all doses (7-12 Gy) examined, no difference in the survival was observed between control and MT-transgenic mice. The average survival times between control and MT-transgenic mice were also similar. Leukocytes were decreased 78 +/- 7% and 75 +/- 11% in control and MT-transgenic mice respectively 5 days after radiation. Furthermore, MT-transgenic mice were also equally susceptible as control mice to the lethal toxic effects produced by cyclophosphamide (1.75 mmol/kg, i.p.). In summary, MT-I transgenic mice are not protected against the toxic effects produced by gamma-radiation or cyclophosphamide.