Acute resistance exercise increases the expression of chemotactic factors within skeletal muscle
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Intense resistance exercise causes mechanical loading of skeletal muscle, followed by muscle adaptation. Chemotactic factors likely play an important role in these processes.
We investigated the time course of changes in the expression and tissue localization of several key chemotactic factors in skeletal muscle during the early phase of recovery following resistance exercise.
Muscle biopsy samples were obtained from vastus lateralis of eight untrained men (22 ± 0.5 years) before and 2, 4 and 24 h after three sets of leg press, squat and leg extension at 80 % 1-RM.
Monocyte chemotactic protein-1 (95×), interleukin-8 (2,300×), IL-6 (317×), urokinase-type plasminogen activator (15×), vascular endothelial growth factor (2×) and fractalkine (2.5×) mRNA was significantly elevated 2 h post-exercise. Interleukin-8 (38×) and interleukin-6 (58×) protein was also significantly elevated 2 h post-exercise, while monocyte chemotactic protein-1 protein was significantly elevated at 2 h (22×) and 4 h (21×) post-exercise. Monocyte chemotactic protein-1 and interleukin-8 were expressed by cells residing in the interstitial space between muscle fibers and, in some cases, were co-localized with CD68 + macrophages, PAX7 + satellite cells and blood vessels. However, the patterns of staining were inconclusive and not consistent.
In conclusion, resistance exercise stimulated a marked increase in the mRNA and protein expression of various chemotactic factors in skeletal muscle. Myofibers were not the dominant source of these factors. These findings suggest that chemotactic factors regulate remodeling/adaptation of skeletal muscle during the early phase of recovery following resistance exercise.
KeywordsResistance exercise Adaptation Myokines Skeletal muscle
Glyceraldehyde 3-phosphate dehydrogenase
Monocyte chemotactic protein-1
Reverse transcription polymerase chain reaction
Tumor necrosis factor-α
Urokinase-type plasminogen activator
Vascular endothelial growth factor
We thank Dr. Andrew Garnham (Deakin University) for all muscle biopsy procedures and the participants for volunteering. The PAX7 (developed by Atsushi Kawakami) and Collagen IV (M3F7, developed by Dr. Heinz Furthmayr) primary antibodies were obtained from the Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by The University of Iowa, Department of Biology, Iowa City, IA 52242.
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