The chemical form of cadmium in microsomal and mitochondrial fractions from rat liver and kidney after long term administration of cadmium chloride.

Wistar rats were given drinking water containing 250 ppm cadmium (Cd) for 12 months. After excising the kidney and liver, the organs were subfractionated into nuclear, mitochondrial, microsomal and cytosol fractions, and the chemical forms of Cd in the subcellular fractions were examined. Although approx. 90% of the total Cd was present in the cytosol, in the form of metallothionein, 3-5% was also present in the mitochondrial fraction and 5-7% in the microsomal fraction from both organs. Each membrane fraction was washed 3 times and there was no contamination of metallothionein from the cytosol according to Cd/protein ratios. By Sephadex G-75 gel filtration, after solubilizing the particulate fractions with sodium deoxycholate, approx. 89% of Cd in the microsomal fraction and 94% in the mitochondrial fraction eluted with the same retention time as that of metallothionein in both liver and kidney, while the remainder was found in a high molecular weight protein fraction. The Cd eluted with the high molecular protein fraction might be involved in dysfunctions in subcellular organelles.