Lysosomal changes in mouse skeletal muscle during the repair of exercise injuries

Comparative label-free mass spectrometric analysis of temporal changes in the skeletal muscle proteome after impact trauma in rats

Proteomics offers the opportunity to identify and quantify many proteins and to explore how they correlate and interact with each other in biological networks. This study aimed to characterize changes in the muscle proteome during the destruction, repair, and early-remodeling phases after impact trauma in male Wistar rats. Muscle tissue was collected from uninjured control rats and rats that were euthanized between 6 h and 14 days after impact injury. Muscle tissue was analyzed using unbiased, data-independent acquisition LC-MS/MS. We identified 770 reviewed proteins in the muscle tissue, 296 of which were differentially abundant between the control and injury groups (P ≤ 0.05). Around 50 proteins showed large differences (≥10-fold) or a distinct pattern of abundance after injury. These included proteins that have not been identified previously in injured muscle, such as ferritin light chain 1, fibrinogen γ-chain, fibrinogen β-chain, osteolectin, murinoglobulin-1, T-kininogen 2, calcium-regulated heat-stable protein 1, macrophage-capping protein, retinoid-inducible serine carboxypeptidase, ADP-ribosylation factor 4, Thy-1 membrane glycoprotein, and ADP-ribosylation factor-like protein 1. Some proteins increased between 6 h and 14 days, whereas other proteins increased in a more delayed pattern at 7 days after injury. Bioinformatic analysis revealed that various biological processes, including regulation of blood coagulation, fibrinolysis, regulation of wound healing, tissue regeneration, acute inflammatory response, and negative regulation of the immune effector process, were enriched in injured muscle tissue. This study advances the understanding of early muscle healing after muscle injury and lays a foundation for future mechanistic studies on interventions to treat muscle injury.

Proteomic identification of potential markers of myosteatosis in human urine

Myosteatosis, the infiltration of fat in skeletal muscle, is associated with lower skeletal muscle density (SMD) as detected by computed tomography (CT). It increases with aging and obesity and is thought to play a role in the aetiology of insulin resistance and type II diabetes. The clinical significance of myosteatosis in cancer cachexia, however, remains to be determined. Along with demonstrable subcutaneous and visceral lipolysis, myosteatosis may also be a key component of the syndrome. We aimed to investigate the use of human urine as a non-invasive way to screen for molecular biomarkers of myosteatosis/reduced SMD using SELDI-TOF mass spectrometry. Pre-operative CT scans of patients undergoing surgery for upper gastrointestinal or hepatopancreaticobiliary cancer were analysed at the level of the third lumbar vertebrae. Myosteatosis was inferred as the presence of reduced SMD, which was defined as Hounsfield units for skeletal muscle <39.5 (two standard deviations below a normal healthy cohort). Urine was analysed by mass spectrometry using CM10 and IMAC30 SELDI-chips. Peaks observed in the CM10 and IMAC30 chip types, showed marked expressional differences between control and myosteatosis, were further investigated by mascot SELDI matrix matching. A total of 55 patients was recruited; 31 patients were found to be myosteatotic on CT scan. Application of the IMAC30-derived model to the entire cohort showed a sensitivity of 97%, specificity of 71% and an overall correctness of 85%. Application of the CM10 chipset-based model to the entire cohort, showed a 77% sensitivity, 67% specificity and 73% overall correctness. Analysis of the peaks of interest resulted in the identification of significant fragments of cathepsin C, argin, arylsulfatase A and glial fibrillary acidic protein. We identified several potential urinary molecular biomarkers associated with reduced SMD in cancer. Such markers are potentially useful in deriving a clinical screening test for myosteatosis.

Delay in post-ovariectomy estrogen replacement negates estrogen-induced augmentation of post-exercise muscle satellite cell proliferation

This study examined the effects of a delay in post-ovariectomy replacement of 17β-estradiol (estrogen) on the post-exercise proliferation of muscle satellite cells. Nine-week-old, ovariectomized, female Sprague-Dawley rats (n = 64) were distributed among 8 groups based on estrogen status (0.25 mg estrogen pellet or sham), exercise status (90 min run at 17 m·min(-1) and a grade of -13.5° or unexercised), and estrogen replacement ("proximal", estrogen replacement within 2 weeks; or "delayed", estrogen replacement at 11 weeks following ovariectomy). Significant increases in satellite cells were found in the soleus and white gastrocnemius muscle (immunofluorescent colocalization of nuclei with Pax7) 72 h following eccentric exercise (p < 0.05) in all exercised groups. Proximal E2 replacement resulted in a further augmentation of muscle satellite cells in exercised rats (p < 0.05) relative to the delayed estrogen replacement group. Expression of PI3K was unaltered and phosphorylation of Akt relative to total Akt increased following estrogen supplementation and exercise. Exercise alone did not alter the expression levels of Akt. An 11 week delay in post-ovariectomy estrogen replacement negated the augmenting influence seen with proximal (2 week delay) post-ovariectomy estrogen replacement on post-exercise muscle satellite cell proliferation. This effect appears to be independent of the PI3K-Akt signaling pathway.

Oestrogen-dependent satellite cell activation and proliferation following a running exercise occurs via the PI3K signalling pathway and not IGF-1

AIM

The purpose of this study was to determine whether 17β-estradiol (E2) enhances the activation, proliferation and differentiation of muscle satellite cells (SC) following eccentric exercise either via insulin-like growth factor-1 (IGF-1) or through phosphatidylinositol 3-kinase (PI3K) signalling.

METHODS

This study used 64, 9-week-old, ovariectomized Sprague-Dawley rats that were divided into eight treatments groups based on oestrogen status (0.25 mg oestrogen pellet or sham), exercise status (90 min run @ 17 m min(-1), -13.5° or unexercised) and PI3K signalling inhibition (0.7 mg wortmannin kg(-1) body weight or DMSO control).

RESULTS

Significant increases in total SCs were found in both soleus and white gastrocnemius muscles (immunofluorescent co-localization of Pax7(+) nuclei) 72 h following eccentric exercise (P < 0.05). Oestrogen supplementation caused a further enhancement in total SCs in exercised rats (P < 0.05). In animals where the PI3K pathway was inhibited, regardless of oestrogen or exercise status, there was no significant enhancement of SC number in both the soleus or white gastrocnemius muscles. Interestingly, oestrogen supplementation lowered muscle levels of IGF-1 with this effect being most prominent in the soleus muscle. While IGF-1 was increased following exercise (P < 0.05), oestrogen supplementation abrogated this increase back to sedentary levels.

CONCLUSION

These data suggest that the increase in SC population following exercise in oestrogen-supplemented females may be mediated via PI3K pathway signalling and not IGF-1.

Gross ultrastructural changes and necrotic fiber segments in elbow flexor muscles after maximal voluntary eccentric action in humans

Eccentric muscle actions are associated with ultrastructural changes. The severity and types of change depend on the nature of the stimulation protocol, and on the method for assessing such changes, and can be regarded as a continuum from mild changes to pathological-like changes. Most studies describing more severe changes have been performed on animals and only a few in humans, some using electrical stimuli. Hence, a debate has emerged on whether voluntary actions are associated with the pathological-like end of the continuum. The aim of this study was to determine whether severe muscle damage, i.e., extensive ultrastructural changes, is confined to animal studies and studies on humans using electrical stimuli. Second, because there is no generally approved method to quantify the degree of muscle damage, we compared two published methods, analyzing the Z disks or sarcomeres, as well as novel analyses of pathological-like changes. A group of untrained subjects performed 70 voluntary maximal eccentric muscle actions using the elbow flexors. On the basis of large reductions in maximal force-generating capacity (on average, −62 ± 3% immediately after exercise, and −35 ± 6% 9 days later), five subjects were selected for further analysis. Biopsies were taken from m. biceps brachii in both the exercised and nonexercised arm. In exercised muscle, more disrupted (13 ± 4 vs. 3 ± 3%) and destroyed (15 ± 6 vs. 0%) Z disks were found compared with nonexercised muscle. A significant proportion of exercised myofibers had focal (85 ± 5 vs. 11 ± 7%), moderate (65 ± 7 vs. 11 ± 6%), and extreme (38 ± 9 vs. 0%) myofibrillar disruptions. Hypercontracted myofibrils, autophagic vacuoles, granular areas, central nuclei, and necrotic fiber segments were found to various degrees. The present study demonstrates that the more severe end of the continuum of ultrastructural changes occurs in humans after voluntary exercise when maximal eccentric muscle actions are involved.

Protective effects of Panax ginseng on muscle injury and inflammation after eccentric exercise

Eccentric muscle contraction causes fibre injury associated with disruption of the myofibrillar cytoskeleton. The medicinal plant Panax ginseng C.A. Meyer, known for its therapeutic properties, was studied to explore its protective effects after eccentric contraction. A crude extract and a standardised extract (G115) of different saponin compositions were tested as to their efficacy in reducing lipid peroxidation, inflammation and release of myocellular proteins after the realisation of an eccentric contraction protocol on a rat treadmill. Plasma creatine kinase (CK) levels were significantly reduced by approximately 25% after ingestion of both extracts of ginseng. Both extracts reduced lipid peroxidation by approximately 15% as measured by malondialdehyde levels. beta-Glucuronidase concentrations and glucose-6-phosphate dehydrogenase (G6PDH) levels, which can be considered markers of inflammation, were also significantly reduced. The values of beta-glucuronidase were increased from 35.9+/-1.5 to 128.4+/-8.1 in vastus and to 131.1+/-12.1 U x g(-1) in rectus, the protection due to ginseng administration being approximately 40% in both muscles. Both extracts appeared to be equally effective in reducing injuries and inflammation caused by eccentric muscle contractions.

Lack of cytosolic and transmembrane domains of type XIII collagen results in progressive myopathy

Type XIII collagen is a type II transmembrane protein found at many sites of cell adhesion in tissues. Homologous recombination was used to generate a transgenic mouse line (Col13a1(N/N)) that expresses N-terminally altered type XIII collagen molecules lacking the short cytosolic and transmembrane domains but retaining the large collagenous ectodomain. The mutant molecules were correctly transported to focal adhesions in cultured fibroblasts derived from the Col13a1(N/N) mice, but the cells showed decreased adhesion when plated on type IV collagen. These mice were viable and fertile, and in immunofluorescence stainings the mutant protein was located in adhesive tissue structures in the same manner as normal alpha1(XIII) chains. In immunoelectron microscopy of wild-type mice type XIII collagen was detected at the plasma membrane of skeletal muscle cells whereas in the mutant mice the protein was located in the adjacent extracellular matrix. Affected skeletal muscles showed abnormal myofibers with a fuzzy plasma membrane-basement membrane interphase along the muscle fiber and at the myotendinous junctions, disorganized myofilaments, and streaming of z-disks. The findings were progressive and the phenotype was aggravated by exercise. Thus type XIII collagen seems to participate in the linkage between muscle fiber and basement membrane, a function impaired by lack of the cytosolic and transmembrane domains.

Acute exercise induced changes in rat skeletal muscle mRNAs and proteins regulating type IV collagen content

This experiment tested the hypothesis that running-induced damage to rat skeletal muscle causes changes in synthesis and degradation of basement membrane type IV collagen and to proteins regulating its degradation. Samples from soleus muscle and red and white parts of quadriceps femoris muscle (MQF) were collected 6 h or 1, 2, 4, or 7 days after downhill running. Increased muscle beta-glucuronidase activity indicated greater muscle damage in the red part of MQF than in the white part of MQF or soleus. In the red part of MQF, type IV collagen expression was upregulated at the pretranslational level and the protein concentration decreased, whereas matrix metalloproteinase-2 (MMP-2), a protein that degrades type IV collagen, and tissue inhibitor of metalloproteinase-2 (TIMP-2), a protein that inhibits degradation, were increased in parallel both at mRNA and protein levels. Type IV collagen mRNA level increased in the white part of MQF and soleus muscle. The protein concentration increased in the white part of MQF and was unchanged in soleus muscle. MMP-2 and TIMP-2 changed only slightly in the white part of MQF and soleus muscle. The changes seem to depend on the severity of myofiber injury and thus probably reflect reorganization of basement membrane compounds.

Lack of type XV collagen causes a skeletal myopathy and cardiovascular defects in mice

Type XV collagen occurs widely in the basement membrane zones of tissues, but its function is unknown. To understand the biological role of this protein, a null mutation in the Col15a1 gene was introduced into the germ line of mice. Despite the complete lack of type XV collagen, the mutant mice developed and reproduced normally, and they were indistinguishable from their wild-type littermates. However, Col15a1-deficient mice showed progressive histological changes characteristic for muscular diseases after 3 months of age, and they were more vulnerable than controls to exercise-induced muscle injury. Despite the antiangiogenic role of type XV collagen-derived endostatin, the development of the vasculature appeared normal in the null mice. Nevertheless, ultrastructural analyses revealed collapsed capillaries and endothelial cell degeneration in the heart and skeletal muscle. Furthermore, perfused hearts showed a diminished inotropic response, and exercise resulted in cardiac injury, changes that mimic early or mild heart disease. Thus, type XV collagen appears to function as a structural component needed to stabilize skeletal muscle cells and microvessels.

Lack of type XV collagen causes a skeletal myopathy and cardiovascular defects in mice

Type XV collagen occurs widely in the basement membrane zones of tissues, but its function is unknown. To understand the biological role of this protein, a null mutation in the Col15a1 gene was introduced into the germ line of mice. Despite the complete lack of type XV collagen, the mutant mice developed and reproduced normally, and they were indistinguishable from their wild-type littermates. However, Col15a1-deficient mice showed progressive histological changes characteristic for muscular diseases after 3 months of age, and they were more vulnerable than controls to exercise-induced muscle injury. Despite the antiangiogenic role of type XV collagen-derived endostatin, the development of the vasculature appeared normal in the null mice. Nevertheless, ultrastructural analyses revealed collapsed capillaries and endothelial cell degeneration in the heart and skeletal muscle. Furthermore, perfused hearts showed a diminished inotropic response, and exercise resulted in cardiac injury, changes that mimic early or mild heart disease. Thus, type XV collagen appears to function as a structural component needed to stabilize skeletal muscle cells and microvessels.

Gender differences in skeletal muscle fibre damage after eccentrically biased downhill running in rats

Specific antibodies against structural proteins of muscle fibres (actin, desmin, dystrophin) and extracellular matrix (fibronectin) were used to study the effect of eccentrically biased downhill running exercise (13,5 degrees, 17 m min(-1), 130 min) on the magnitude and properties of myofibre injury in the quadriceps femoris muscle of male and female rats. Muscle beta-glucuronidase activity, a quantitative indicator of muscle damage, showed clearly smaller increase in female than in male rats during the 4-day period following exercise. A similar course of histopathological changes was observed in both sexes, although females showed slower and less marked changes than males. In males, discontinuous or even lost submembrane protein dystrophin staining was observed in some swollen fibres immediately after exercise, before the loss of desmin and staining of disorganized actin, i.e. before the disruption of the cytoskeletal system and the contractile apparatus. The observation that no dramatic changes in the microarchitecture of the muscle fibres were detected immediately or even 6 h after the exercise in females compared with males may indicate that the sarcolemma of the females might be strengthened against membrane damage by a still unknown stabilizing compound.

Submaximal exercise in the cold: does cooling potentiate the development of muscle injuries in the rat?

To test the effect of low ambient temperature on muscular strain and possible development of muscle injuries, male Sprague-Dawley rats (n = 35) were exercised at a speed of 15 m min-1 on a treadmill at a 6 degrees inclination for 1.5 h in a warm (22 degrees C) or a cold (-10 degrees C) environment. Blood and tissue samples were collected 0 and 48 h postexercise. Blood glucose, lactate, pyruvate, cortisol, epinephrine (E) and norepinephrine (NE) were determined to investigate the effect on energy metabolism. To estimate the degree of physical strain, possible muscle injury and regenerative processes of muscles in response to exercise in the cold, serum creatine kinase (CK), lactate dehydrogenase (LDH), muscle beta-glucuronidase and prolyl-4-hydroxylase (PH) activities were measured. In addition, histology of the hindlimb muscles m. soleus and m. tibialis anterior was examined. In general, the circulating level of metabolic substrates during exercise were unaffected by the exercise and independent of ambient temperature. Plasma cortisol increased significantly during exercise (P < 0.01), but was unaffected by the thermal strain. Of the myocellular enzymes, serum CK increased by 100% (P < 0.01) and LDH by 93% (P < 0.05) during exercise in the cold compared with exercise in warm, indicating a higher physical strain. However, exercise in the cold did not result in muscle injuries as judged by the unaltered muscular beta-glucuronidase, PH levels and muscle morphology. It is concluded that the exercise type and intensity used caused stress that was independent of the ambient temperature. In addition, the rats were able to maintain unaltered circulating levels of energy substrates also in the cold. Finally, exercise in the cold increased muscular strain but did not result in muscle injuries.

Exercise-induced changes in the activities of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase in plasma and muscle of standardbred trotters

The activities of lysosomal enzymes, such as beta-glucuronidase and N-acetyl-beta-D-glucosaminidase, have been shown to increase in muscle after endurance exercise. We examined whether measurable activities of lysosomal enzymes are present in equine plasma and whether the exercise-induced changes in the muscle are reflected in plasma. Six trained Standardbred trotters performed three exercise bouts with 1 h intervals and the same procedure was repeated 3 days later. Venous blood samples and muscle biopsies from the middle gluteal muscle were taken before and after exercise. The activities of beta-glucuronidase and N-acetyl-beta-D-glucosaminidase were measured both from plasma and muscle specimens. Cell infiltration into the muscle after exercise was evaluated by the DNA content and histochemically by haematoxylin stain. The activity of N-acetyl-beta-D-glucosaminidase in plasma was increased immediately after exercise, but had returned to the basal level at 4 h. N-acetyl-beta-D-glucosaminidase in muscle and beta-glucuronidase in muscle and plasma increased 2 days after exercise and returned to the basal level on day 3. A similar pattern was seen when the exercise protocol was repeated 3 days later, except that the activities continued to increase during the 3 days after exercise. The DNA content in muscle correlated with beta-glucuronidase in muscle and plasma and with the N-acetyl-beta-D-glucosaminidase in muscle indicating that the activities reflect the infiltration of phagocytes into the exercise-injured muscle. It can be concluded that the activities of the lysosomal enzymes in plasma increase after exercise and that the changes are mainly due to a simultaneous increase in the number of neutrophils. Therefore, plasma activities of the lysosomal enzymes are poor indicators of exercise-induced muscle damage.

Effects of electromyostimulation and strength training on muscle soreness, muscle damage and sympathetic activation

Electromyostimulation (EMS) is known to develop muscular strength and hypertrophy. The aim of this study was to compare EMS exercise-induced damage with concentric (CONC) exercise-induced damage. Twelve male athletes were randomly assigned to concentric exercise (five sets of 6 voluntary contractions) or to EMS (30 contractions of 6 s duration, 20 s rest between contractions) on day 0 (D0). The load was 80% of the maximal isometric force. Criterion measures of plasma creatine kinase (CK) activity and lactate dehydrogenase (LDH) activity, and subjective ratings of muscle soreness and urinary catecholamines, were assessed 1 day before and for 3 days after exercise. Among the members of the EMS group, there were significant increases in catecholamine urinary excretion, especially adrenaline (on days D+2 and D+3), plasma CK activity (on day D+2) and plasma LDH activity (on days D+1 and D+2). The changes among the members of the CONC group were smaller and no significant difference was noted. Muscular soreness was greatest in the EMS group, with the peak occurring on day D+2. Comparisons of enzyme release, muscular soreness and urinary catecholamines suggest that EMS induces myofibre membrane damage and a significant increase in sympathetic nervous activity.

Exercise-induced necrotic muscle damage and enzyme release in the four days following prolonged submaximal running in rats

Male Wistar rats were made to run uphill on a treadmill 5.5 degrees incline at 17 m min-1 for 4 h, and killed for muscle and serum sampling 2, 4, 12, 24, 48 or 96 h after the exertion. To estimate the degree of muscle damage, beta-glucuronidase activity, total protein concentration, water content and morphology were examined in the red parts of quadriceps femoris (MQF) and soleus (MS) muscles, the distal white part of the rectus femoris muscle (MRF) and the superficial part of triceps brachii muscle (MTB). Simultaneous serum samples were assayed for creatine kinase (CK) activity and carbonic anhydrase III (CA III) concentration. Fibre swelling and interstitial oedema were detected in MS at 4 h and in MQF at 12 h and typical histopathological changes, including inflammation and fibre necrosis, in both muscles 12-96 h post-exertion. beta-Glucuronidase activity, a quantitative marker of muscle damage, was increased in MS at 4 h, in MQF at 24 h and in MRF 48 h after the running. No increase occurred in MTB. Water and protein content increased or decreased respectively, faster in MS (2 h post-exercise) than in MQF (12 h) or MRF (12 h). Water content thus contributed to muscle damage by preceding the increase in beta-glucuronidase activity. Serum CK activity was increased 2, 4, and 48 h after the running. Changes in serum CA III concentration were rather similar to those in CK but were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Microtrauma to rat superficial masseter muscles following lengthening contractions

Repetitive lengthening contractions have been predicted as a mechanism causing injury, pain, and delayed soreness in the hyperactive masticatory muscle. This mechanism was examined by the mechanical lengthening of the contracted superficial masseter (SM) muscle in anesthetized rats. Repetitive stimulation of the left SM to tetanic tension was followed by mechanical lengthening, which stressed contracted muscle. The contralateral muscle was passively lengthened repetitively. Contractile tension in response to a varying frequency of stimulation was measured in pre- and post-lengthened SM muscles. A selective loss of force at all frequencies up to 100 Hz occurred in the muscles subjected to lengthening contractions. Low-frequency fatigue did not occur in SM muscles passively lengthened. All animals recovered without loss of weight or dehydration. They were killed at 24 or 72 h post-lengthening. The SM muscles were collected, and no significant differences were found in mean weight, length, or cross-sectional area when the right and left SM muscles were compared at 24 or 72 h. Two observers independently examined histological secretions of SM muscles and graded the localized inflammatory sites on a scale of 1-4. A non-parametric statistical test was used so that the inflammatory scale for each muscle could be ranked. There were significantly more injured sites in SM muscles subjected to lengthening contractions, compared with the lengthened (but relaxed) SM muscles. The SM muscles of anesthetized rats were internally injured by repetitive lengthening contractions, and they exhibited low-frequency fatigue. These findings support the hypothesis that repetitive lengthening contractions in the masticatory muscle could be a mechanism for the pain and dysfunction of masticatory muscles in humans with certain parafunctional habits.

Acquisition of a lysosomal enzyme by myoblasts in tissue culture

Skeletal muscle myoblasts from different sources acquired high levels of the lysosomal enzyme beta-glucuronidase, when they were cultured together with mitogen-activated lymphocytes. Immunofluorescent staining, thermal stability, and electrophoretic mobility showed that the increase in enzyme activity in the myoblasts was due to the presence of the lymphocyte form of the enzyme. Although myoblasts were able to take up exogenous beta-glucuronidase from the culture medium by mannose 6-phosphate receptor-mediated endocytosis, enzyme acquisition during co-culture with lymphocytes was independent of this pathway. Enzyme transfer from the lymphocytes was found to require direct cell-cell contact with the muscle cells, and was accompanied by an increase in beta-glucuronidase activity in the lymphocytes themselves. Since this additional activity was also due to the presence of the lymphocyte form of the enzyme, these results indicate that interaction with the muscle cells induced the de novo synthesis of beta-glucuronidase in the lymphocytes.

Increased susceptibility to lipid peroxidation in skeletal muscles of dystrophic hamsters

The results showed that the total content of lipids, which could be peroxidized with Fe(2 +)/ascorbate stimulation in vitro, was 45.4% and 53.7% higher than normal in the dystrophic hamster muscle at the age of 1 and 3 months, respectively. Correspondingly, the susceptibility to lipid peroxidation (stimulated by ADP-chelated iron at 37 degrees C) was 38.6-74.3% higher in dystrophic muscles. The increases were not related to necrotic lesions and inflammation observed. The activities of glucose-6-phosphate dehydrogenase, glutathione reductase, thioredoxin reductase and catalase were increased in dystrophic muscles but those of superoxide dismutases and glutathione peroxidase were unaffected.

Exercise-induced lipid peroxidation and leakage of enzymes before and after vitamin E supplementation

1. The purpose of this study was to investigate the effects of vitamin E on serum levels of malondialdehyde following the acute exhaustive exercise in human, and to determine whether the magnitude of leakage of enzyme would be affected by vitamin E supplementation. 2. Increase of malondialdehyde after exercise before vitamin E supplementation was slight (but statistically significant), however after supplementation with vitamin E, malondialdehyde level after exercise was significantly decreased. 3. Leakage of enzyme was significantly increased after exercise before vitamin E supplementation, but it was lower following exercise after vitamin E supplementation. 4. Lipid peroxidation following a bout of acute heavy exercise can be inhibited by vitamin E supplementation.

Food deprivation decreases the exertion-induced acid hydrolase response in mouse skeletal muscle

Strenuous prolonged running causes muscle fibre necrosis in skeletal muscles. The muscle injury is associated with inflammation and a strong increase in the total activities of certain acid hydrolases a few days after exertion. The activity changes of acid hydrolases quantitatively well reflect the severity of histopathological changes during the myopathy (for review see Salminen, Acta Physiol Scand [Suppl 539] 1985). In this study male NMRI-mice were exposed to a protocol of fasting and refeeding together with or without a 6 h run on a treadmill at 13.5 m.min-1. The animals were killed 4 days after the exercise and samples from the red part of quadriceps femoris were analyzed for arylsulfatase (ASase) and beta-glucuronidase (GUase) activities. Starvation protocols did not affect ASase or GUase. Running caused a 3.2-fold increase in ASase and a 5.1-fold increase in GUase. If mice were exercised in the fasted condition a normal exercise response occurred in both activities, but when mice were exercised 2 days after the finish of fasting the exercise response was greatly diminished. Thus food deprivation followed by 2 days refeeding induces a protection against exercise myopathy in mice. The protection greatly resembles that induced by regular endurance training preceding strenuous prolonged exertion.

Morphological and enzymatic heterogeneity of suramin-induced lysosomal storage disease in some tissues of mice and rats

Suramin-induced lysosomal storage disease reproduced in the rat was extended to the mouse with the attempt to characterize enzymatically and morphologically heterogeneous responses of various organs to the drug. Suramin administration strikingly decreased (3-6 days afterward) the activity of beta-glucuronidase in all tissues studied (kidney, liver, heart, and skeletal muscle). The enzymatic responses were small in the activities of beta-N-acetyl-glucosaminidase. The activity of arylsulfatase A decreased to a varying degree in mouse tissues, but in rats the activity increased in liver and skeletal muscle. The activity of cathepsin D increased in rat tissues. Suramin induced morphological changes characteristic to lysosomal storage diseases in kidney and liver but not in heart and skeletal muscle of both mice and rats. Kidney was appreciably more susceptible to suramin than liver. The occurrence of lysosomal accumulations, membranous lamellar inclusions, and granular material were most prominent in tubular cells of kidney and in Kupffer cells of liver. These cells also presented intensive Alcian blue staining. Interestingly, the enzymatic and morphological responses did not correlate with each other, which may reflect differences in the regulation of lysosomal functions in various cell types.