Heavy metals in the spinal cord of normal rats and of animals treated with chelating agents: a quantitative (zinc, copper, and lead) and histochemical study.

The amounts of zinc, copper, and lead in the rat spinal cord were determined by means of flameless atomic absorption spectrophotometry. Zinc was present in a concentration about 100 p.p.m. (dry weight), copper in a concentration about 5 p.p.m., and lead in slightly more than 1 p.p.m. Analysis of various levels along the cranio-caudal axis of the rat spinal cord revealed differences in the heavy metal content. The Timm sulfide silver staining method has demonstrated that metals in the spinal cord have a distinct regional distribution. To obtain a differentiation between the stainable metals, the effects of six chelating agents (DEDTC, dithizone, oxine, EDTA, dipyridyl, and phenantroline) on the Timm pattern were tested. EDTA left the pattern unchanged, while the other compounds showed individual differences in their influence on the Timm pattern, suggesting that the heavy metal pattern of the spinal cord consists of multiple compartments. The effect of intravital multiple low dose treatment with three of the chelating agents on the histochemical pattern and the metal content of the spinal cord was also investigated. It was found that a decrease in the metal content was not followed by reduction of stainability and vice versa.