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

Abstract

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 resorption 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 resorption was measured isotopically by the loss of 3H-tetracycline from each whole bone. Bone growth was quantified in terms of relative and absolute increase in bone calcium mass. When the rates of bone resorption (loss of [3H]-tetracycline as percent of whole bone per 3 weeks) were compared between sexes, the six axial bones showed significantly higher rates (P < 0.05-0.001) in males (64-73) than in females (37-66). No significant sex differences were observed in rate for the two cranial and two appendicular bones. During 4-7 weeks of age, a comparison of bone masses showed that only one bone (calvaria) gained more mass in the male and two bones (mandible and humerus) gained more mass in the female. In contrast, five of six axial bones gained more mass in the female. Thus, 7 out of 10 bones were larger in the female. In growing male and female rats, an inverse relationship appears between rate of bone resorption and mass for most of the axial bones; this relationship was not apparent for cranial or appendicular bones. Sexual dimorphism was consistently seen by greater axial bone mass in females. However, greater rates of bone resorption were seen in male axial bones but not in cranial or appendicular bones. It is apparent that the different types of bones are heterogeneous in their rates of resorption and formation during this period of growth.

Two-week longitudinal survey of bone architecture alteration in the hindlimb-unloaded rat model of bone loss: sex differences

“…In Fischer 344 rats, females also had a greater trabecular bone volume and a higher bone formation rate than males in the proximal metaphysis of tibia (13). In 1-to 1.5-mo-old Sprague-Dawley rats, lower resorption rates along with greater bone mass were reported in females compared with males in the axial skeleton but not in cranial and appen- dicular (humerus and femur) bones (31). Sexual dimorphism may result from different growth rates between the sexes, where one sex develops faster than the other in the same time interval.…”

Effects of collagen/β-tricalcium phosphate bone graft to regenerate bone in critically sized rabbit calvarial defects

“…29 In fact, the resorption of β-TCP, which is important for bone formation, may be promoted using such growth factors as fibroblast growth factor-2 64 or bone morphogenetic protein-2 (BMP-2). 65 Furthermore, since bones have different resorption and formation rates, 66 scaffold biodegradation might occur more rapidly in maxillary defects than in calvarial defects. 47 Thus, modifying the scaffold preparation process could be a suitable way to achieve complete scaffold resorption.…”

“…Furthermore, since bones have different resorption and formation rates, 66 scaffold biodegradation might occur more rapidly in maxillary defects than in calvarial defects. 47 Thus, modifying the scaffold preparation process could be a suitable way to achieve complete scaffold resorption.…”

Inverse correlation between trabecular bone volume and bone marrow adipose tissue in rats treated with osteoanabolic agents

“…Female rats have been observed to reach skeletal and sexual maturity sooner than males. At the time female growth attenuates, males continue to grow and accrue skeletal mass [29,30]. Female rats, like women, may experience fluctuations in hPTH levels, or higher hPTH levels earlier in life, that potentially cause increased bone acquisition earlier than males, which may be related to estrogen signaling as well [31][32][33].…”