VISUALIZATION OF YELLOWISH-ORANGE LUMINESCENCE FROM CUPROUS METALLOTHIONEINS IN LIVER OF LONG-EVANS CINNAMON RAT

We describe the first use of an emission probe, based on the cuprous t hiolate chromophore, for direct microscopical observation of cuprous m etallothioneins located in liver of 15-week-old (just before spontaneo us hepatitis) Long-Evans Cinnamon rats. The rats show remarkable accum ulations of copper and cuprous metallothioneins. In the mildly fixed l iver, we visualized the same yellowish-orange luminescence as the spec ific emission from cuprous metallothioneins, following excitation in 3 30-385 nm region. In liver from Long-Evans Agouti rat, a counter part of Long-Evans Cinnamon rat, no similar luminescence was found. So, it was thought that cuprous metallothioneins accumulated in the Long-Evan s Cinnamon rat liver might emit the yellowish-orange light, To verify this presumption, we tentatively defined three histochemical criteria, quenching tests by oxidation, protonation and mercury treatment, base d on the coordination chemical characteristics of metallothioneins. Th e emission completely satisfied these criteria. Furthermore, the relia bility of these criteria was supported by immunocytochemical and bioch emical results. Consequently, all results sufficiently indicate that t he yellowish-orange luminescence in the Long-Evans Cinnamon rat liver is the emission from cuprous metallothioneins.