Inhibitory effect of cadmium on collagenous peptide synthesis of embryonic chick bone in tissue culture

Relationship between osteoid formation and iron deposition induced by chronic cadmium exposure in ovariectomized rats

Itai-itai (Japanese, "It hurts! It hurts!") disease (IID), a form of osteomalacia, can be induced in ovariectomized rats by long-term administration of cadmium (Cd). This IID rat model shows severe anemia, severe nephropathy, and osteomalacia accompanied by iron (Fe) deposition at the mineralization front. We characterized the pathogenesis of Cd-induced bone lesions by investigating the relationship between Fe deposition and osteoid tissue formation in ovariectomized rats. The rats were injected with CdCl₂ (0.5 mg/kg) for 70 weeks, with or without co-injection of erythropoietin (EPO) for varying lengths of time to elucidate whether EPO prevents and/or cures anemia, and, with the restoration from anemia, lessens the osteoid tissue formation. Necropsies were performed at 25, 50, or 70 weeks. Fe deposition at the mineralization front of bone was found at 50 weeks and increased thereafter. Animals injected with EPO showed decreased Fe deposition, although there was no relation between EPO administration and osteoid formation in the femur. Because the increase in bone lesion severity was independent of the amount of Fe deposition, we suggest that Fe deposition is not involved in the etiology of Cd-induced femoral bone lesions.

Mechanism for bone disease found in inhabitants environmentally exposed to cadmium: decreased serum 1 alpha, 25-dihydroxyvitamin D level

To investigate the mechanism for bone disease caused by exposure to cadmium serum samples were collected from 5 itai-itai disease patients, 36 Cd-exposed residents with renal tubular damage and 17 non-exposed individuals and analyzed for 1 alpha,25-dihydroxyvitamin D[1 alpha,25(OH)2D], parathyroid hormone, beta 2-microglobulin, calcium and inorganic phosphorus. Measurement of percentage tubular reabsorption of phosphate (%TRP) were performed only on the Cd-exposed subjects. Serum 1 alpha,25(OH)2D levels were lower in itai-itai disease patients and cadmium-exposed subjects with renal damage than in non-exposed subjects. Parathyroid hormone and beta 2-microglobulin concentrations in serum were higher in the Cd-exposed subjects. Decrease in serum 1 alpha,25(OH)2D levels were closely related to serum concentrations of parathyroid hormone, beta 2-microglobulin and %TRP. This study suggests that cadmium-induced bone effects were mainly due to a disturbance in vitamin D and parathyroid hormone metabolism, which was caused by the cadmium-induced kidney damage.