Effects of Dietary NaCl Supplementation on Bone Synthesis of Hydroxyproline, Urinary Hydroxyproline Excretion and Bone ⁴⁵Ca Uptake in the Rat

Summary

High sodium chloride intakes are regarded as a risk factor for osteoporosis because they increase the obligatory urinary calcium loss and stimulate parathyroid activity. Sodium chloride loads induce osteopenia in the rat. The effect could be due to a decrease in bone formation or a rise in bone resorption. Two experiments were undertaken to study the effects of dietary NaCl supplementation on ³H-hydroxyproline synthesis and ⁴⁵Ca uptake in femoral bone. Salt-treated rats excreted 1.7 times more total urinary hydroxyproline (P < 0.001) and 2.1 times more recently labelled ³H-hydroxyproline than controls (P < 0.02) but they did not accumulate less ³H-hydroxyproline or less ⁴⁵Ca in their bones than controls. These results indicate that salt-mediated osteopenia is due to an increase in bone resorption, rather than to a decrease in bone formation.

Key-Words

Osteoporosis - Sodium Chloride - Bone Resorption - Bone Formation