Effects of microgravity on the mouse triceps brachii muscle

ABSTRACT Introduction: In this study we investigated the effects of microgravity on the fiber properties of the mouse triceps brachii, a forelimb muscle that has no antigravity function. Methods: Mice (n = 7) were exposed to microgravity for 13 days on the space shuttle Atlantis (Space Transportation System‐135). The fiber cross‐sectional area (CSA) and succinate dehydrogenase (SDH) staining intensity of the triceps brachii muscle were compared with those of controls (n = 7). SDH activity in this muscle was also estimated. Results: Microgravity did not affect the body weight, muscle weight, or fiber CSA, but there was reduced SDH staining intensity of all types of fibers, irrespective of the muscle region (P