Effect of gender on bone turnover in adult rats during simulated weightlessness

Abstract

Prologned spaceflight results in bone loss in astronauts, but there is considerable individual variation. The goal of this rat study was to determine whether gender influences bone loss during simulated weightlessness. Six-month-old Fisher 344 rats were hindlimb unweighted for 2 wk, after which the proximal tibiae were evaluated by histomorphometry. There were gender differences in tibia length, bone area, cancellous bone architecture, and bone formation. Compared with female rats, male rats had an 11.6% longer tibiae, a 27.8% greater cortical bone area, and a 37.6% greater trabecular separation. Conversely, female rats had greater cortical (316%) and cancellous (145%) bone formation rates, 28.6% more cancellous bone, and 30% greater trabecular number. Hindlimb unweighting resulted in large reductions in periosteal bone formation and mineral apposition rate in both genders. Unweighting also caused cancellous bone loss in both genders; trabecular number was decreased, and trabecular separation was increased. There was, however, no change in trabecular thickness in either gender. These architectural changes in cancellous bone were associated with decreases in bone formation and steady-state mRNA levels for bone matrix proteins and cancellous bone resorption. In conclusion, there are major gender-related differences in bone mass and turnover; however, the bone loss in hindlimb unweighted adult male and female rats appears to be due to similar mechanisms.

Effects of Sex and Gender on Adaptation to Space: Musculoskeletal Health

“…However, in mature rats few differences between genders are apparent. 19 There is little definitive evidence showing sex-specific differences in the rate of bone loss. Certainly, some of the individual differences may be related to sex-specific hormonal factors.…”

Interleukin-15 responses to aging and unloading-induced skeletal muscle atrophy

“…The HS model of unloading has been widely used in rodents to study the effects of unloading on bone (22) and muscle (2,3,16,38). In the current study and others (3,24,32), HS has been used to examine the interaction of aging and unloading.…”

Regulation of bone mineral density in the grey squirrel, Sciurus carolinensis: Bioavailability of calcium oxalate, and implications for bark stripping

“…However, this was based on a low‐carbohydrate, high‐fat diet, so it is unlikely grey squirrels are showing a differential response to the custom‐made diets. Sex differences were also identified in rats in response to simulated weightlessness (Hefferan et al., 2003), which can be thought of as a special kind of disuse osteoporosis (Milstead, Simske, & Bateman, 2004). Variable bone turnover in males and females led to differences in bone architecture in response to hind‐leg unloading (Hefferan et al., 2003).…”

“…Sex differences were also identified in rats in response to simulated weightlessness (Hefferan et al., 2003), which can be thought of as a special kind of disuse osteoporosis (Milstead, Simske, & Bateman, 2004). Variable bone turnover in males and females led to differences in bone architecture in response to hind‐leg unloading (Hefferan et al., 2003). Whilst the squirrels were not subjected to this level of immobilisation, and they were restricted to an individual cage, which resulted in reduced activity compared to that which would normally occur in the wild (Gurnell, 1987).…”