Early cellular effects of circulating cadmium-thionein on kidney proximal tubules

Circulating cadmium-thionein (Cd-MT) is cleared from the mammalian circulatory system by filtration through the kidney glomerulus with subseqent reabsorption by kidney proximal tubules. Damage to the tubules results following uptake of Cd-MT, which is dependent upon time and the dose level of cadmium administered. Intravenous administration of 109Cd-MT at doses of 0.017 and 0.17 mg Cd/kg body weight disclosed that the rate of clearance from the blood and uptake by the kidney was significantly more rapid at the 0.017 mg Cd/kg dose. Ultrastructural changes were characterized by increased numbers of pinocytotic vesicles and small, dense lysosomal structures. There was no evidence of mitochondrial swelling or cell death at either 3 or 6 h after injection. Results suggest that Cd-MT is reabsorbed and broken down by kidney tubule cells in a physiological manner with possible subsequent release of the toxic cadmium ion