Effect of 1,25-dihydroxyvitamin D3 on bone metabolism in tissue culture. Enhancement of the steroid effect by zinc.

The present investigation was undertaken to clarify the interaction of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and zinc on bone metabolism in tissue culture. Calvaria were removed from weanling rats (3-week-old males) and cultured for periods up to 96 hr in Dulbecco's Modified Eagle Medium (high glucose, 4500 mg/dl) supplemented with antibiotics and bovine serum albumin. The experimental cultures contained 10(-10) to 10(-6) M 1,25(OH)2D3. All cultures were incubated at 37 degree in 5% CO2/95% air. Bone calcium content was increased significantly by the presence of 10(-9) to 10(-7) M 1,25(OH)2D3. The steroid (10(-9) to 10(-7) M) also significantly increased alkaline phosphatase activity in the bone, whereas it did not alter significantly acid phosphatase activity. [3H]Leucine incorporation by the bone was raised significantly by 10(-8) to 10(-7) M 1,25(OH)2D3. Furthermore, bone DNA content was increased significantly by 10(-9) to 10(-7) M 1,25(OH)2D3. Meanwhile, the presence of 10(-4) M zinc, which can stimulate bone formation, significantly enhanced the effect of 10(-7) M 1,25(OH)2D3 to increase alkaline phosphatase activity and DNA content in rat calvaria. The present study demonstrates that 1,25(OH)2D3 has a direct stimulatory effect on bone metabolism in tissue culture and that zinc can enhance the steroid effect.