Effects of Streptomycin Administration on Increases in Skeletal Muscle Fiber Permeability and Size Following Eccentric Muscle Contractions

Abstract

The purpose of this study was to investigate the preventive effect of streptomycin (Str) administration on changes in membrane permeability and the histomorphological characteristics of damaged muscle fibers following eccentric contraction (ECC ). Eighteen 7-week-old male Fischer 344 rats were randomly assigned to three groups: control (Cont), ECC, and ECC with Str (ECC + Str). The tibialis anterior (TA) muscles in both ECC groups were stimulated electrically and exhibited ECC. Evans blue dye (EBD), a marker of muscle fiber damage associated with increased membrane permeability, was injected 24 hr before TA muscle sampling. The number of EBD-positive fibers, muscle fiber cross-sectional area (CSA), and roundness were determined via histomorphological analysis. The ECC intervention resulted in an increased fraction of EBD-positive fibers, a larger CSA, and decreased roundness. The fraction of EBD-positive fibers was 79% lower in the ECC + Str group than in the ECC group. However, there was no difference in the CSA and roundness of the EBD-positive fibers between the two ECC groups. These results suggest that Str administration can reduce the number of myofibers that increase membrane permeability following ECC, but does not ameliorate the extent of fiber swelling in extant EBD-positive fibers. Anat Rec, 301:1096-1102, 2018. © 2018 Wiley Periodicals, Inc.

Myofiber Permeability and Force Production of Rat Muscles Following Eccentric Contractions: The Repeated Bout Effect Depends on the Interval

“…These groups included the non-ECC (Control) group (n = 8); the single-injury (Post 1st bout) group (n = 8); groups allowed to recover for 1, 2, and 4 weeks after a single injury (the Pre 2nd bout_1w, Pre 2nd bout_2w, and Pre 2nd bout_4w groups; n = 8 per group); and groups subjected to second injuries at 1-, 2-, and 4-week intervals (the Post 2nd bout_1w, Post 2nd bout_2w, and Post 2nd bout_4w groups; n = 8 per group) ( Figure 1). The appropriate sample size (n = 8 per group) was calculated with reference to EBD-positive fiber data from a previous study conducted in our laboratory using the following formula [9]: rats were anaesthetized, and muscle samples were obtained. EBD was intraperitoneally administered 24 h prior to the collection of muscle samples, and the maximal isometric contraction tension was measured immediately prior to muscle sampling.…”

“…EBD was intraperitoneally administered twenty-four hours prior to the collection of muscle samples, and the maximal isometric contraction tension was measured immediately prior to muscle sampling. The first and second bouts of ECC were set to the same load strength and were performed as described in a previous study [9]. Briefly, the left TA muscles of the rats in each ECC group were electrically stimulated under 2% isoflurane inhalation anaesthesia.…”

“…To assess the myofibers responsible for increasing membrane permeability, rats received an intraperitoneal injection of 1% EBD solution (E2129; Sigma-Aldrich, St. Louis, MO, USA) at a volume of 1% of the body mass (1 mg EBD/0.1mL phosphate-buffered saline [PBS]/10g of body mass) 24 h prior to TA muscle collection [9,31]. Maximal isometric contraction tension was measured in the Post 1st bout and Post 2nd bout groups 2 days after the last ECC intervention.…”

“…Excessive ECC increases membrane permeability, causes creatine kinase to leak out of myofibers [7], into the plasma, and causes extracellular proteins such as albumin to enter myofibers [8]. Infiltration of extracellular fluid causes myofibers to become swollen and opaque [9]. The main pathways for extracellular fluid entry into myofibers following ECC have been reported to be membrane tears and stretch-activated channels [10].…”

“…EBD is water soluble and membrane impermeable, has high binding affinity for serum albumin, and can be used to detect damaged myofibers. Positive staining for glyoxal-bis (2-hydroxyanil) (GBHA) (a free calcium indicator) has been observed in EBD-stained infiltrated myofibers after ECC [9]. Excessive increases in intracellular calcium ions promote the production of calcium dependent proteases, such as calpain and phospholipases, which causes myofiber membrane damage and disruption in intermediate filament proteins, such as desmin, that link myofibrils laterally to each other [11][12][13][14].…”