A highly sensitive method for the histochemical demonstration of copper in normal rat tissues.

Earlier, widely used histochemical methods for the demonstration of copper are capable of detecting only extremely high tissue levels of this metal (generally only in pathological states, e.g. Wilson's disease, or in cases of copper intoxication), because of their low sensitivity. The specificity of these methods has also proved to be unsatisfactory. We present a new method based on the release of bound (unreactive) copper by trichloroacetic acid, its primary precipitation using magnesium dithizonate, and intensification of the staining (secondary precipitation) using silver nitrate. Using this method, copper is demonstrable in various tissues of normal rats (brain, stomach, liver, small intestine, spleen, pancreas, kidneys) in the form of reddish to pink staining. This method can also be applied to locate pathologically high levels of copper.