A. Salminen

Acid hydrolase activity in red and white skeletal muscle of mice during a two-week period following exhausting exercise

The activities of β-glucuronidase, β-N-acetylglucosaminidase, arylsulphatase, ribonuclease,p-nitrophenylphosphatase, and malate dehydrogenase together with protein content were assayed from representative mixed (m. rectus femoris), predominantly red (proximal heads ofm. vastus lateralis, m.v. medius andm. v. intermedius), and predominantly white (distal head ofm. vastus lateralis) muscle homogenates of mice during a two-week period following one single exposure to exhausting intermittent running on a treadmill. The activities of cathepsin D and β-glycerophosphatase were assayed from mixed muscle only. In all three muscle types, particularly in red muscle, the activities of β-glucuronidase, β-N-acetylglucosaminidase, arylsulphatase, and ribonuclease progressively increased between one to five days after the exercise; thereafter the activities began to decrease, being near the control values 15 days after the exercise. In mixed muscle, cathepsin D activity increased. No corresponding changes were observed in the activities of acid phosphatases.The time course of the activity changes closely resembled that earlier found to be caused by ischaemia in rabbit muscles. It is tentatively concluded that the two treatments, exhaustive exercise and temporary ischaemia, cause similar cell injuries, and that the lysosomal system involved seems to function similarly in the post-stress recovery of the fibres from these injuries.

Exhaustive physical exercise and acid hydrolase activity in mouse skeletal muscle

SummaryAdult, untrained NMRI mice were exhausted on a motor-driven treadmill by an intermittent-type running programme. Serial cryostate sections for the staining of NADH-tetrazolium reductase, β-glucuronidase, β-N-acetylglucosaminidase, and β-glycerophosphatase activities and for making hematoxylin-eosin staining were cut from m. quadriceps femoris 1, 2, 3, 5, 7, and 15 days after physical exhaustion. A strong increase in the activities of β-glucuronidase and β-N-acetylglucosaminidase, was observed 7 days after exhaustion and the activity changes, which were similar for the both glycosidases, were more prominent in the highly oxidative red compared to less oxidative white fibres. Activity granules were more numerous in the perinuclear than the interfibrillar area of red fibres. Spots were arranged like longitudinal chains between myofibrils. Activity in connective tissue was usually observed only in animals exhausted 3–7 days earlier. Simultaneous activity in fibres exceeded that in connective tissue β-Glycerophosphatase activity was not, by the method used, seen in histologically “healthy” or normal-looking fibres. in samples taken 2–5 days after exhaustion some degenerating and necrotic fibres were observed. Inflammatory reaction was also observed being at its strongest five days after loading when mononuclear cells were seen inside necrotic fibres. The number of regenerating muscle cells was most abundant 7 days after exhaustion. It is suggested that temporary hypoxia, which accompanies exhaustive physical exercise in skeletal muscle, upsets the energy metabolism and homeostasis of fibres and causes the observed histological and histochemical alterations, which posses features typical of both lethal and sublethal acute cell injury.

Acid proteolytic capacity in mouse cardiac and skeletal muscles after prolonged submaximal exercise

Acid proteolytic capacity in mouse cardiac muscle and in predominantly white (distal head of m. vastus lateralis) or predominantly red (proximal red heads of m. vastus lateralis, m. v. medialis, and m. v. intermedius) skeletal muscle was estimated 5 days after 3 h, 6 h or 9 h prolonged running at a speed of 13.5 m/min. The activities of acid protease and β-glucuronidase together with the rate of acid autolysis considerably increased in both skeletal muscle types, especially in red muscle, but did not increase in cardiac muscle. Acid proteolytic capacity and β-glucuronidase activity increased in relation to the duration of running. Protein content and oxidative capacity (the activities of citrate synthase and malate dehydrogenase) decreased in red skeletal muscle after 6 h and 9 h running. In white muscle only protein content slightly decreased after 9 h running. No corresponding changes were observed in cardiac muscle. Histopathological changes were traced in mixed skeletal muscle (m. rectus femoris). Necrotic lesions were observed in the red superficial area of m. rectus femoris after 6 h and, in particular, after 9 h running. The results show that prolonged submaximal running also produces lethal and sublethal skeletal muscle fibre injuries, as well as exhaustive exercise or temporary ischaemia as reported earlier. It is suggested that sublethal injuries precede lethal ones and that acid proteolytic capacity increases especially in the sublethally injured muscle fibres.

Increased activities of prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyltransferase, enzymes of collagen biosynthesis, in skeletal muscle of endurance-trained mice

The activities of prolyl 4-hydroxylase (PH) and galactosylhydroxylysyl glucosyltransferase (GGT), and the concentration of 4-hydroxyproline were measured in red and white parts of quadriceps femoris muscle of mice after 3, 10, and 20 sessions of daily endurance training. The activities of PH and GGT increased in the red part of the muscle after training for 3 and 10 times and returned to the control level after 20 training sessions. In the white muscle the increase of PH activity was less than in the red muscle. No alteration in GGT activity was observed in the white muscle. The concentration of hydroxyproline was unchanged in the both types of skeletal muscle. The results suggest that collagen turnover in leg muscles may be enhanced during the early phase of adaptation to endurance training. The enhancement is more prominent in red than in white skeletal muscle.

Age- and sex-related differences in lipid peroxidation of mouse cardiac and skeletal muscles

1. The purpose of the present study was to characterize age- and sex-related changes in lipid peroxidation capacities and enzymatic antioxidants of cardiac and skeletal muscles in NMRI-mice (Mus musculus). 2. Lipid peroxidation rates (unstimulated and enzymatic/iron-stimulated) strongly decreased in skeletal muscle during ageing. 3. Unstimulated lipid peroxidation rate but not that of stimulated, also decreased in cardiac muscle. 4. The total level of Fe2+/ascorbate-stimulated non-enzymatic lipid peroxidation was not, however, affected by ageing. 5. The activity of catalase slightly increased in cardiac muscle and that of glutathione peroxidase in skeletal muscle during ageing. 6. Unstimulated lipid peroxidation rate was significantly higher in the skeletal muscle of male than female mice. 7. Correspondingly, the Fe2+/ascorbate-stimulated lipid peroxidation capacities of microsomal and mitochondrial fractions of skeletal muscle were significantly higher in male mice. 8. The activity of glutathione peroxidase as well as the concentration of lipofuscin were higher in the cardiac muscles of female than male mice.

Chronic hydrogen peroxide intake and peroxide metabolizing enzyme activities in some tissues of mice and rats.

Chronic daily intake of 0.5% H2O2 in drinking water decreased Se-dependent glutathione peroxidase (Se-GSHPx) activity in rat skeletal muscle, kidney and liver. Non-Se GSHPx activity decreased in kidney. Deprivation of drinking water decreased Se-GSHPx activity in kidney and non-Se GSHPx activity in kidney and liver. H2O2 intake decreased activity of catalase in rat skeletal muscle. H2O2 intake or water deprivation caused no changes in these enzyme activities in mice.

Prednisolone decreases exercise-induced acid hydrolase response in mouse skeletal muscle.

SummaryMale NMRI-mice were subjected to exhaustive treadmill exercise. 3 and 6 days after the exertion, quadriceps femoris muscles were examined histologically and analyzed for acid hydrolases in order to follow the degree and progress of injuries. Prednisolone (PRED), an anti-inflammatory corticosteroid, was given to some of the animals in order to modify the exercise response. The PRED administration began 14 h before exercise and continued until the end of the experiment (6 days). The doses were 25 and 50 mg·kg−1 i.p. twice a day. The activities of both arylsulphatase andΒ-glucuronidase increased significantly in the exercise control group after 3 and 6 days. The increase in activity correlated with fibre necrosis and an abundant infiltration of inflammatory cells, and was greatest after 3 days. After 6 days the inflammatory response decreased and regenerating muscle fibres were seen. PRED decreased the exercise-induced acid hydrolase response. The decrease was most prominent after 3 days with PRED 50 mg·kg−1·day−1. PRED also diminished degeneration and inflammation. The results suggest that the decrease in acid hydrolase activities was due to a lesser infiltration of inflammatory cells to the injured area.

Enzymatic and nonenzymatic lipid peroxidation capacities and antioxidants in hypoxic and reoxygenated rat myocardium

The effects of 60 min hypoxia and subsequent reoxygenation for 30 min on enzymatic (NADPH-dependent) and nonenzymatic (Fe2+/ascorbate-induced) lipid peroxidation capacities and on antioxidant levels were studied using Langendorff-perfused rat hearts. The assays were done on the myolayer of the right ventricle (RV) and on the subepi- and subendomyolayers of the left ventricle (epi/endo LV) after normoxic, hypoxic, and reoxygenation phases. The region injured by hypoxia/reoxygenation was located mainly in endo LV, seen as a lesser penetration of the fluorescent dye fluorescein in the myocardium. The electron microscopic findings after reoxygenation revealed swelling of the mitochondria, amorphous mitochondrial structures, and formation of paracrystallines. The myofibrillar structure of the cells was disrupted and the cells showed marked fluid accumulation. Membrane structures were marginated and formed blebs and multilamellar bodies. Ultrastructural changes were most prominent in endo LV, especially after reoxygenation. The increase in leakage of lactate in the perfusate revealed the onset of anaerobic metabolism. Abrupt release of the cytoplasmic enzymes lactate dehydrogenase and creatine kinase at the beginning of the reoxygenation phase suggested cell membrane injury. The capacity for Fe2+/ascorbate-induced lipid peroxidation slightly increased in RV and that for NADPH-dependent, enzymatic lipid peroxidation in endo LV after reoxygenation. Catalase, glutathione peroxidase, and superoxide dismutase activities remained unchanged, whereas glucose-6-phosphate dehydrogenase activity decreased after reoxygenation in RV.(ABSTRACT TRUNCATED AT 250 WORDS)

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°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.

Activities of some antioxidative and hexose monophosphate shunt enzymes of skeletal muscle in neuromuscular diseases

ABSTRACT The activities of some antioxidative and hexose monophosphate shunt enzymes, as well as of 2 hydrolases were studied in skeletal muscle biopsy specimens taken from 39 patients with neuromuscular diseases and from 15 controls. The activity of Se‐dependent glutathione peroxidase was higher in patients with congenital myotonia, whereas in the other diagnostic groups this enzyme activity was the same as in the controls. The Se‐independent and total glutathione peroxidase activity of patients in the various diagnostic groups did not differ from the controls. Moreover, no difference were observed in catalase activity between the patient groups and the controls. The activities of the rate limiting enzymes of hexose monophosphate shunt, glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase of muscle biopsy samples of various patient groups did not show any significant difference from controls. The activity of a lysosomal hydrolase, β‐N‐acetylglucosaminidase, was increased in patients with polyneuropathy and the activity of a nonlysosomal protease, alkaline protease, was high in patients with Charcot‐Marie‐Tooth disease. The activities of Se‐dependent glutathione peroxidase, 6‐phosphogluconate dehydrogenase and of both hydrolases showed a significant correlation to the magnitude of muscle atrophy.