Effects of 1.25 dihydroxyvitamin D3 on calcium metabolism in rats exposed to cadmium.

The radioisotopic study of calcium metabolism in the rat after chronic oral administration of cadmium (8 mg/kg) has shown two different effects: a) in the intestine cadmium inhibits the absorption of calcium by active transport; b) in the deep bone compartment, the decrease of the bone calcium used for the crystallization goes together with a reduction of the exchange rates between this compartment and the central compartment (serum extracellular and soft tissues calcium). The simultaneous oral administration of 1.25 dihydroxyvitamin D3 (80 ng/kg) even though it increases significantly the calcium intestinal absorption factor does not allow the various parameters of bone calcium metabolism to stay within normal values. In spite of the arrest of osteolysis and of an strong increase of osteogenesis (superficial bone balances and alkaline phosphatases) the loss of calcium caused by cadmium in the deep bone is not compensated.