Comparison of the mechanism of action of vitamin D3 and 1 alpha-OH D3 under conditions of experimental hypercalcemia.

Comparison of the mechanism of action Vitamin D3 and 1 alpha-OH D3 under conditions of experimental hypercalcemia. Acta Physiol. Pol. 1979, 30 (2): 313--318. The hypercalcemic effect of supraphysiological doses of Vitamin D and 1 alpha-OH D3 were compared applying an animal model. Changes in serum calcium of animals with normal dietary calcium supplementation and those under conditions of calcium depletion were analyzed. Dietary calcium is necessary for the hypercalcemic effect of Vitamin D, whereas in case of 1 alpha-OH D3 calcium is mobilized not only from the dietary but also from some other sources. The analysis of the hypercalcemia kinetics in the Vitamin D and 1 alpha-OH D3 treated animals indicated that the kidney 1 hydroxylase of 25 hydroxycholecalciferol is an important step in the hypercalcemia preventing mechanism.