Immobilization and bone mass in rats

It is concluded that parathyroidectomy and acetazolamide administration, both of which are known to inhibit bone resorption, are effective in significantly reducting the development of the bone mass changes, seen after denervation of the limb in the rat.

Abstract

The effects of parathyroidectomy and acetazolamide on the changes in bone mass which occur following immobilization were studied in male and female rats. The forelimb was immobilized by sectioning the right brachial nerve plexus. At 10 to 14 days following denervation, both humeri were removed. The dry weight of the bones was determined and the difference between the weight of the bones from the intact and denervated, limbs was used at an index of the denervation response. Animals were either parathyroidectomired or placed on a diet containing 0.5% acetazolamide sodium at the time of denervation. Parathyroidectomy inhibited the development of the denervation response to the extent of 45%, 30%, and 85% in three experiments. Acetazolamide, incorporated as the sodium salt in laboratory chow at a concentration of 0.5%, also blocked the development of the denervation response. In three experiments, treatment with the drug for 10 to 14 days inhibited the response 42%, 47%, and 64% respectively. Under conditions of pair-feeding 0.5% acetazolamide incorporated in the diet caused a slight but significant hypercalcemia. It is concluded that parathyroidectomy and acetazolamide administration, both of which are known to inhibit bone resorption, are effective in significantly reducting the development of the bone mass changes, seen after denervation of the limb in the rat.