Abstract
Many studies have investigated the physiological response to microgravity in both astronauts and animals. However, while space agencies have sought to deploy more women on their missions; animal models rarely include females studies or comparisons between males and females. Therefore, we exposed adult female rats to 2 weeks of partial weight-bearing at either 100% of their normal loading (PWB100) or 40% of their normal loading (PWB40), corresponding to Martian gravity-analog, and assess muscle function, force and histomorphometry. Females exposed to PWB showed an 11.62% decline in hindlimb grip force associated with an 11.84% decrease in soleus myofiber size after 14 days of exposure, while maintaining normal blood oxygenation and stress levels. This pilot study represents the first experiment designed to understand the muscular disuse associated with a partial reduction in mechanical loading in female rats, and the first step needed to develop successful mitigating strategies.New and NoteworthyThis research article describes the first use of quadrupedal partial weight-bearing in female rats. This study demonstrates the feasibility of partial gravity analogs in females and allows for future investigations about the impact of sex on muscle deconditioning due to reduced mechanical loading.
Highlights
Despite National Aeronautics and Space Administration (NASA)’s being created in 1958, and the first American man, Alan Shepherd, having entered space in 1961, the first woman to serve as an astronaut, Sally Ride, did not reach space until 1983 (Muller, 2005)
PWB40 animals did not experience any significant variations in their body weight, both compared to the control group and to their pre-suspension value (Figure 1B); daily food intake was similar across both groups (Figure 1C)
While cumulative food intake at 7 and 14 days did not differ between the two groups, when normalized to the animals’ body weight, it was significantly greater in the PWB40 group at 14 days (Figure 1D)
Summary
Despite NASA’s being created in 1958, and the first American man, Alan Shepherd, having entered space in 1961, the first woman to serve as an astronaut, Sally Ride, did not reach space until 1983 (Muller, 2005). Our recently developed rat partial weight-bearing (PWB) analog has proven to be a reliable (Mortreux et al, 2018) and consistent (Mortreux et al, 2019a) model, and when combined with the hindlimb suspension via pelvic harness (HLS), can be used to represent an additional period in microgravity (Mortreux et al, 2019c), mimicking a trip to and from these extraterrestrial bodies. This PWB model has only been used in adult male rats far (Mortreux et al, 2019b).
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