Age-dependent stimulation or inhibition of calcium release from bone cultures by 1 alpha, 25-dihydroxyvitamin D3

The effect of 1 alpha, 25-dihydroxyvitamin D3 (1 alpha, 25-(OH)2D3) on calcium release from neonatal and young adult mouse calvaria in tissue culture was studied. At concentrations from 2.6 X 10(-6) M to 2.6 X 10(-9) M, 1 alpha 25-(OH)2D3 enhanced calcium release from 5-day-old calvaria. At the same concentrations, 1 alpha, 25-(OH)2D3 either inhibited or failed to enhance calcium release from 75-day-old calvaria. Parathyroid hormone-enhanced calcium release from 75-day-old calvaria was inhibited considerably by 1 alpha, 25-(OH)2D3 at 2.6 X 10(-6) M and 2.6 X 10(-7) M. These findings suggest that cells involved in the bone resorption process may respond differently to the same stimulus at different stages in the development of the organism. This direct inhibitory effect of 1 alpha, 25-(OH)2D3 on bone resorption in cultured calvaria of older animals may explain, in part, its beneficial effect in the treatment of osteoporosis.