Sex differences in absolute rates of bone resorption in young rats: appendicular versus axial bones.

This study compares absolute rates of bone resorption and formation at the organ level in adolescent Sprague-Dawley rats as a function of sex and type of bone. Bone r’esorption and formation were quantified in rapidly growing male and female rats (4-7 weeks of age) who were multiply prelabeled with [3H]tetracycline. Ten different whole bones were compared: four cranial or appendicular bones and six axial bones. Absolure rate of bone r’esorption was measured isotopically by the loss of3H-tetracycline from each whole bone. Bone growth was quantified in terms of relative and absolute increase in bone calcium mass.