Radiation exposure does not alter metallothionein III isoform expression in mouse brain

The level of metallothionein III mRNA and protein, a brain-specific isoform of metallothionein (MT), was investigated in the brain of MT-I and -II gen e knockout (MT-null) mice exposed to 20 Gy whole-body gamma-irradiation. Be cause MT-null mice did not express MT-I or MT-II isoforms, the total brain MT content in these mice represented the isoform MT-III only. MT-III protei n content was determined by a cadmium-binding assay, and the MT mRNA level was measured by reverse transcription followed by polymerase chain reaction (RT-PCR). Both MT-III protein content and mRNA expression in the brains of MT-null mice were not affected by exposure to whole-body irradiation. Thes e results indicate that mouse brain MT-III expression is not induced by ion izing radiation.