Meeting Abstract

P2.146  Sunday, Jan. 5 15:30  Increasing mechanical strain on the skeleton during reproduction does not reduce bone mobilization during reproduction in the mouse HOBENSACK, M.J.*; HOOD, W.R.; Auburn University; Auburn University mjh0026@auburn.edu

Bone is a dynamic tissue with minerals being deposited or withdrawn according to the demands of the body. During late pregnancy and lactation, female mammals mobilize mineral from bone to support the ossification of offspring skeleton(s). Conversely, in response to mechanical loading, minerals are deposited in bone enabling it to develop a stronger architecture. Despite their central importance to the functionality of vertebrate individuals, the interactions between these potentially opposing forces of mineral deposition in response to mechanical strain and mineral mobilization in response to reproduction remains poorly understood. It is possible that inter-individual differences in the loading imposed by different forms of locomotion may alter the amount of mineral mobilized during reproduction. Here, the impact of climbing on bone mobilization was examined during reproduction in the laboratory mouse. Mice were divided among treatment groups. The climbing group had access to a 60-cm tower, increasing strain on their appendicular skeleton. The tunnel group had access to a 100-cm tunnel, which encouraged movements within the horizontal plane. Mothers’ in the climbing group displayed changes in femoral trabeculae that reflected net gain in bone, whereas changes in the mid-shaft cortical bone reflected a net loss of bone. The mineral content of mothers’ femurs and body did not differ between groups. The total body mineral content of individual offspring and the cumulative amount of mineral invested in the full litter, corrected for litter size, was also similar between treatment groups. These results suggest that a redistribution of femoral bone may allow mothers to resist strain while maintaining high calcium output to suckling young.