title: Skeletal response to simulated weightlessness: a comparison of suspension techniques.
abstract: The skeletal response to simulated weightlessness was studied in rats subjected to two different methods of suspension. Skeletal unloading of the hind limbs for a two week period was achieved by use of either a back harness or tail traction. In comparison to pair-fed control rats, back-suspended rats failed to gain weight whereas tail-suspended rats exhibited normal weight gain. Quantitative bone histomorphometry revealed marked skeletal abnormalities in the proximal tibial metaphysis of back-suspended rats. Loss of trabecular bone mass in these animals was due to a combination of depressed longitudinal bone growth, decreased bone formation, and increased bone resorption. In contrast, the proximal tibia of tail-suspended rats was relatively normal by these histologic criteria. However, a significant reduction in trabecular bone volume occurred during 2 weeks of tail suspension, possibly due to a transient inhibition of bone formation during the early stages of skeletal unloading. Lack of weight gain in back-suspended rats may be indicative of a pronounced stress response during which corticosteroids adversely affected the skeleton. Maintenance of normal weight gain by tail-suspended rats provides evidence for the less traumatic nature of this method of suspension. Our findings indicate that tail suspension may be a more appropriate model for evaluating the effects of simulated weightlessness on skeletal homeostasis.
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D000818:Animals; D001846:Bone Development; D001853:Bone Marrow / Q000033:anatomy & histology; D001842:Bone and Bones / Q000033:anatomy & histology* / Q000166:cytology; D008297:Male; D008722:Methods; D051381:Rats; D011919:Rats, Inbred Strains; D014893:Weightlessness