Abstract
Skeletal muscle crush injuries occur in an incident when the limb is trapped with a compressing force. Little is known about the recovering mechanisms of injured muscles. To study these, we developed a new apparatus. For induction of crush injury, a pressure of 4.25 kg/cm2 was applied for 2 h on the left lower limb of the rat. We examined changes in their histological and physiological properties. We report that slow fibers play important roles in recovery of skeletal muscles from such injury. A follow-up survey was done for 8 weeks on 12 species of hind limb muscles; their wet-weight, number of fibers, diameter and area of fibers were measured. Slow fibers were identified by immunohistological staining. Muscle function was analyzed from footprint. Soon after the crush, wet-weight of muscles increased by 10-20% in 1-2 days (acute edematous phase), decreased by 30% during 2 days to 2 weeks (atrophic phase) and then increased gradually for 8 weeks (recovery phase). Diameter and area of muscle fibers, which reduced in the first 2 weeks, started to increase gradually in the recovery phase. At 8 weeks, muscle weight exceeded 100% of the control (opposite-side muscles) although their fibers were thinner than the control. Immunohistology revealed that slow fibers showed a large increment in number in the recovery phase; it indicates that they play a major role in recovery from the injury. [J Physiol Sci. 2006;56 Suppl:S146]
