Asynchronous Functional, Cellular and Transcriptional Changes after a Bout of Eccentric Exercise in the Rat

Abstract

Thirty eccentric contractions (ECs) were imposed upon rat dorsiflexors (n= 46) by activating the peroneal nerve and plantarflexing the foot ≈40 deg, corresponding to a sarcomere length change over the range 2.27‐2.39 μm for the tibialis anterior and 2.52‐2.66 μm for the extensor digitorum longus. Animals were allowed to recover for one of 10 time periods ranging from 0.5 to 240 h, at which time muscle contractile properties, immunohistochemical labelling and gene expression were measured. Peak isometric torque dropped significantly by ≈40 % from an initial level of 0.0530 ± 0.0009 Nm to 0.0298 ± 0.0008 Nm (P < 0.0001) immediately after EC, and then recovered in a linear fashion to control levels 168 h later. Immunohistochemical labelling of cellular proteins revealed a generally asynchronous sequence of events at the cellular level, with the earliest event measured being loss of immunostaining for the intermediate filament protein, desmin. Soon after the first signs of desmin loss, infiltration of inflammatory cells occurred, followed by a transient increase in membrane permeability, manifested as inclusion of plasma fibronectin. The quantitative polymerase chain reaction (QPCR) was used to measure transcript levels of desmin, vimentin, embryonic myosin heavy chain (MHC), myostatin, myoD and myogenin. Compared to control levels, myostatin transcripts were significantly elevated after only 0.5 h, myogenic regulatory factors significantly elevated after 3 h and desmin transcripts were significantly increased 12 h after EC. None of the measured parameters provide a mechanistic explanation for muscle force loss after EC. Future studies are required to investigate whether there is a causal relationship among desmin loss, increased cellular permeability, upregulation of the myoD and desmin genes, and, ultimately, an increase in the desmin content per sarcomere of the muscle.

Controlled intermittent shortening contractions of a muscle–tendon complex: muscle fibre damage and effects on force transmission from a single head of rat EDL

“…In this study the transcription of desmin was shown to be elevated already 3 h after the shortening exercise. Peters et al (2003) observed significant increases not earlier than 12 h after lengthening exercise, having its peak value 48 h post-exercise. This suggests that sampling of our muscles at a later time after exercise may have shown a more prominent increase in desmin mRNA content.…”

Effects of GaAs laser and stretching on muscle contusion in rats

“…The combination of injury and eccentric stress of stretching may have contributed to weight muscle gain 32 . However, muscle fiber area is a better measurement than absolute muscle weight for the evaluation of skeletal muscle trophism and we found no difference in the muscle fiber across the section area.…”

The role of myostatin and the calcineurin-signalling pathway in regulating muscle mass in response to exercise training in the rainbow troutOncorhynchus mykissWalbaum

“…An inverse relationship between muscle mass and the overall concentration of myostatin active peptide has been demonstrated in several studies with mammals (GonzalezCadavid et al, 1998;Schulte and Yarasheski, 2001;McMahon et al, 2002). Moreover, myostatin expression was significantly upregulated in response to muscle damage and an atrophic stimulus (Wehling et al, 2000;Peters et al, 2003), but downregulated in response to a hypertrophic stimulus (Roth et al, 2003;Walker et al, 2004). A significant reduction of the myostatin active peptide concentration was observed in the groups of rainbow trout that displayed marked exerciseinduced muscle fibre hypertrophy and this inverse relationship was significant.…”