Metallothionein and cadmium, zinc and copper distribution in blood of rats

Remarkable differences in the biochemical fate of Cd2+, Hg2+, CH3Hg+ and thimerosal in red blood cell lysate

The application of a metallomics method revealed that all investigated Hg species bound to hemoglobin and that these interactions are of toxicological significance.

The origin of metallothionein in red blood cells

The origin of metallothionein (MT) in red blood cells (RBCs) from a mouse given cadmium was studied in connection with RBC kinetics. Plasma Cd concentration rapidly decreased 3 hr following 109CdCl2 (2 mg/kg, sc) administration, whereas RBC Cd increased from 2 to 4 days, followed by a gradual decrease. RBC Cd was found to be distributed more in the high-molecular-weight fraction than in the MT fraction 12 hr after administration. But, thereafter, Cd increased rapidly in the MT fraction to show changes with time similar to Cd level in RBCs. Hepatic damage induced in a mouse given 21 injections of Cd, with resultant marked elevation of plasma MT concentrations, did not cause any change in RBC Cd concentration. MT was hardly transferred to RBC when a mouse RBC suspension was incubated with mouse hepatic MT. To examine the relationship of Cd-MT and erythropoietic function, mice in the normal group, the phenylhydrazine-induced anemia group (PH), the transfusion-induced plethora group (TR), and the erythropoietin administered plethora group (TR + EP) were given 109CdCl2. Three days after administration, Cd concentration in its RBCs and its MT fraction remarkably increased in the PH group, and was greatly decreased in the TR group. A significant increase was noted in the TR + EP group as compared with the TR group. These results indicate that MT in the RBCs is formed in erythroblasts.

The possibility of food contamination with cadmium by means of coloured plastics

By using spectrophotometric atomic absorption, the release of cadmium from some plastic materials (polyethylenes, PVC, polystyrene) used for manufacturing containers, wraps and household objects (which are coloured with pigments derived from cadmium compounds) was studied. Subchronic experiments (45 days) were carried out in white Wistar rats with extracts from cadmium-containing plastic in comparison with the pigment alone. The excreted cadmium in urine and the activity of some serum enzymes were determined. Histopathological changes of the main internal organs were observed. It was found that some pigments of the Papion type have the property of releasing cadmium in amounts exceeding the admitted sanitary levels, amounts which proved to be toxic, producing enzymic and histopathological changes in kidneys and testes.

Cadmium, copper, and zinc distribution in blood of rats after long-term cadmium administration

Cd, Cu, and Zn were determined in plasma and blood cells of rats given daily sc injections of 0.5 mg Cd per kilogram of body weight for 4, 8, and 15 wk. The distribution of these metals in the plasma was also examined by Sephadex G-75 chromatography. In the whole blood Cd increased continuously and reached 1.5 micrograms/ml at 15 wk. Plasma Cd was less than 2% of the total Cd in blood at first and increased to 7.8% in the last week. A significant portion of plasma Cd was found in the metallothionein fraction at 4 wk. The Cd in this fraction increased to more than 50% of the plasma Cd after the 15-wk exposure. The rest of the plasma Cd was distributed in high-molecular-weight protein fractions. Blood Cu was up to 1.3-1.4 micrograms/ml (about twice the value for controls) from 4 to 8 wk, but diminished to about a half the control value at 15 wk. These changes were greater in the plasma and parallel to the Cu contents of the ceruloplasmin fraction. A small amount of plasma Cu was found in the metallothionein fraction at 4 wk. In this fraction Cu increased to about 8% of the plasma Cu at the last week. Blood Zn remained almost unchanged at first but decreased in the last week. Most of the plasma Zn was recovered from high-molecular-weight protein fractions, but not from the metallothionein fraction. Metallothionein in the plasma contained more Cu than Cd. Plasma concentrations of Cd bound to this protein were 0.008, 0.029, and 0.104 micrograms/ml, and the Cu/Cd molar ratios were 9.9, 3.4, and 1.1 at 4, 8, and 15 wk, respectively.