Effect of a low-calcium environment on neonatal rat femora in culture.

The effect of a low-Ca environment on neonatal rat femora was investigated in vitro. One-day-old Wistar strain rat femora were cultured in either control (7.47 +/- 0.18 mg Ca/dl) or low-Ca (1.19 +/- 0.08 mg Ca/dl) media. Growth and development were greater in femora in the low-Ca group than in the control group. The femur head was larger in the low-Ca group than in the control group. Roentgenography showed that the total length and head length of femora increased with time in both groups. Calcification of the diaphyseal bone was lower in the low-Ca group than in the control group, while the cartilage cell zone in the femur head widened more in the low-Ca group. The hypertrophic cartilage cell zone widened particularly in the low-Ca group. Alkaline phosphatase activity, cell proliferation and chondroitin sulphate synthesis activity were higher in the low-Ca group, and the protein content increased more in the low-Ca group. However, collagen synthesis was lower in the low-Ca group. In dead bone, chondroitin sulphate synthesis was not observed in either the control or the low-Ca group. The results suggest that cell proliferation and chondroitin sulphate synthesis are mediated and enhanced and that collagen synthesis is weak when organs are placed in a low-Ca environment.