Abstract
The effects of vitamin C (VC) deficiency on bone metabolism were investigated in the VC-requiring osteogenic disorder Shionogi (ODS) rats. The control rats were fed on a VC-supplemented diet (VC-free food and drinking water with VC) for 3 weeks. The VC-deficient Cl and C2 groups were fed on a VC-free diet (VC-free food and drinking water with no VC) for 1 (C1) and 2 (C2) weeks after being fed on the VC-supplemented diet for 2 and 1 week, respectively. The C3 group was fed on the VC-free diet for 3 weeks. The VC-deficient rats of the Cl, C2 and C3 groups gained body weight at a similar rate to that of the control. The alkaline phosphatase (ALP) activities of the serum and femoral bone in the Cl, C2 and C3 groups were also at similar levels to those of the control. However, the tartrate-resistant acid phosphatase (TRAP) activities of the serum and femoral bone in the C2 and C3 groups were significantly higher than those of the control. The femoral calcium contents of the C2 and C3 groups were significantly lower at about 80% of the control level. The hydroxyproline contents of the femur in the C2 and C3 rats were also significantly lower at about 90% and 80% of the control level, respectively. Although VC is required for ALP expression in an in vitro culture of the osteoblast cell line, MC3T3-E1, the ALP activities in the femur were unchanged by VC deficiency in vivo in the present study. In mature rat bone (in vivo), fully differentiated osteoblasts and a collagenous matrix already existed and VC deficiency incresed the TRAP activity. These results suggest that an increase in bone resorption, not a decrease in bone formation, has caused the decrease in bone calcium and hydroxyproline levels during the period of VC deficiency in mature rats.
