A simplified method for quantitating metallothionein in biological tissues

A new method was modified and evaluated as a simple, sensitive and quantitative procedure for measuring metallothionein (MT) in tissues. Heat denatured cytosolic fractions of tissue homogenates were incubated with 109Cd and bovine hemoglobin was added to scavenge Cd not bound to MT. The hemoglobin and excess Cd were separated from the 109Cd-MT by heating. The Cd remaining in the supernatant was a quantitative measure of the MT present. Analysis of Sephadex G-75 and DEAE-ion exchange fractions of liver supernatants from Cd and Zn-treated rats indicated that the assay is specific for MT. Levels of MT in six rat tissues were quantitated in untreated and Cd-treated rats and were consistent with previous studies on tissue levels of MT. Because of its speed and sensitivity, this assay may be useful for measuring MT in large studies where time and expense are limiting factors.