Stimulatory effect of calcitonin on bone formation in tissue culture.

The present investigation was undertaken to clarify the in vitro effect of synthetic [Asu1,7]eel calcitonin (CT) on bone metabolism in tissue culture. Calvaria were removed from weanling rats (3-week-old male) and cultured for periods up to 96 h in Dulbecco's Modified Eagle Medium supplemented with antibiotics and bovine serum albumin. The experimental cultures contained 1.0 to 100 ng/ml CT. All cultures were incubated at 37 degrees C in 5% CO2-95% air. Bone calcium content was increased significantly by the presence of 10 and 100 ng/ml CT. This increase was blocked by the presence of 10(-6) M cycloheximide or 10(-7) M actinomycin D. Bone alkaline phosphatase activity was significantly increased by the presence of 100 ng/ml CT for 48 and 96 h. Bone acid phosphatase activity was not altered significantly by CT (1-100 ng/ml). The incorporation of [3H]proline into the acid-insoluble residues of bone tissue was significantly increased by the presence of CT (1-100 ng/ml) for 96 h. This increase was completely blocked by the presence of 10(-7) M cycloheximide. Bone DNA content was significantly raised by the presence of 10 and 100 ng/ml CT for 96 h. Furthermore, the culture with CT (10 and 100 ng/ml) produced a significant decrease in glucose concentration in the medium. Also, CT (10 and 100 ng/ml) stimulated the production of pyruvic acid from bone tissue. These results suggest that CT had a direct stimulatory effect on bone formation and mineralization in vitro, and that the hormone stimulates energy metabolism in bone cells.