Metallothionein (MT), the synthesis of which can be induced by metalloelement administration, is a known radical scavenger. This study investigated the possible protective effect of MT against acute radiation injury. Manganese chloride (10 mg of manganese/kg) was administered intraperitoneally to male C3H/He mice 24 h prior to irradiation. The paw of each mouse was irradiated locally, and the acute skin reaction was scored daily and averaged. Acute radiation injury of the small intestine was studied using an <tex-math>${\rm LD}_{50/8}$</tex-math> assay and a gut microcolony assay after abdominal irradiation. An <tex-math>${\rm LD}_{50/8}$</tex-math> value represents the radiation dose required to kill 50% of animals within 8 days. The number of microcolonies per tissue section was counted 3.5 days after irradiation. The level of MT in the liver, skin and intestine was determined by a modified <tex-math>${}^{203}{\rm Hg}\text{-binding}$</tex-math> assay. Acute skin reaction was not prevented by manganese pre-administration. The <tex-math>${\rm LD}_{50/8}$</tex-math> values of manganese-pretreated and control mice were 19.4 and 18.4 Gy, respectively. However, the difference was not significant. The number of microcolonies was not significantly different for these two groups in the dose range of 13-19 Gy. The level of MT in the skin and intestine was not increased by administration of manganese, although a sixfold increase was observed in the liver. In conclusion, manganese chloride treatment of mice 24 h prior to irradiation did not significantly protect skin and small intestine against acute radiation injury, because such a treatment did not result in increased levels of MT in the skin and small intestine.

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