Intravenous 1 alpha, 25[OH](2) vitamin D-3 (calcitriol) pulse therapy for bone lesions in a murine model of chronic cadmium toxicosis

The aim of the present study was to clarify the therapeutic effects of 1 al pha, 25[OH](2) vitamin D-3 (calcitriol) pulse injection on bone lesions ind uced in a rat model of chronic cadmium toxicosis. Ovariectomized (OVX) and control-operated (sham-OVX) rats were given repeated intravenous injections of 0.5 mg/kg/day CdCl2 for 70 weeks. The rats were then treated intravenou sly with 0.02 mug/kg/day calcitriol 3 days per week for 8 weeks. CdCl2 treatment induced increases in osteoid volumes of the femur cortex an d trabecula. This change was accompanied by an increase in the volume of ir on deposition at the mineralization front of the trabeculae and a reduction in mineral density. Abnormalities of bone metabolic parameters, which were increases in the blood calcium, inorganic phosphorous, bone-specific alkal ine phosphatase, parathyroid hormone (PTH) and osteocalcin levels, and in t he urine deoxypyridinoline (D-PYR) level, were also induced. Calcitriol treatment increased the blood calcium and inorganic phosphorous levels, and reduced the blood PTH level. Decreases in blood tartrate-resist ant acid phosphatase and urine d-PYR levels were also induced indicating th at bone resorption was suppressed. The findings indicated that the increase d osteoid volume of the cortex and Fe-deposition volume of the trabecula we re improved. These effects or improvements were observed in the sham-OVX ra ts but not in the OVX rats.