AIMIn order to elucidate the underlying mechanism of depressed maximal isometric twitch tension normalized by cross sectional area of muscle strip in unloaded soleus.

METHODSThe soleus and extensor digitorum longus (EDL) muscle strips were perfused in vitro and treated by 2,3-Butanedione monoxime (BDM).

RESULTSThe BDM decreased Pt of soleus and EDL in a concentration-dependent manner. The Pt could restored completely to normal level after washing out BDM. The isometric twitch duration was not altered during 1 mmol/L BDM of perfusion, but was shortened at 10 mmol/L dose. The time from maximal to half Pt in EDL was shorter than that in soleus during 10 mmol/L BDM of perfusion. The inhibitory effects of BDM on myosin ATPase activity were higher in EDL than in soleus. The inhibitory extent of BDM on myosin ATPase activity of soleus and EDL was lower than that on Pt.

CONCLUSIONThese results suggest that reduction in cross-bridge function of skeletal muscle may be one of reasons induced a decrease in its Pt. BDM is not a specific inhibitor on myosin ATPase activity and can affect multiple parts of excitation-contraction coupling in skeletal muscle.

Animals ; Diacetyl ; analogs & derivatives ; pharmacology ; Isometric Contraction ; drug effects ; physiology ; Male ; Muscle Contraction ; drug effects ; physiology ; Muscle, Skeletal ; drug effects ; physiology ; Myosins ; antagonists & inhibitors ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the effect of ascorbic acid (VC) on relaxation of ex vivo Bufo gastrocnemius during sustained isometric contraction.

METHODSDynamic tension of the muscle was recorded under constant voltage stimulation within 7.0 min at 2 s intervals. The rest tension and relaxation rate of the muscle was obtained by weighted fitting to the relaxation process of tension <90% of its peak with a mono-exponential model to characterize the muscular relaxation.

RESULTSVC at 2.0 mmol/L alone or in combination with the inhibitors of the antixoidation enzymes (surperoxide dismutase, glutathione peroxidase and catalase) resulted in negligible alterations in the muscular relaxation kinetics. VC combined with the inhibitor of surperoxide dismutase resulted in significantly lowered relaxation rate while increased rest tension, but VC with the inhibitor of either catalase or glutathione peroxidase showed negligible action. VC combined with the inhibitors of all the 3 enzymes also caused significant effect on the muscular relaxation kinetics, which was similar the effect of VC with superoxide dismutase inhibitor.

CONCLUSIONVC at high concentration may result in oxidative toxicity to the biological system rich in transitional metal ion complexes but with low antioxidation capacity by causing superoxide-mediated oxidative damages.

Animals ; Ascorbic Acid ; pharmacology ; Bufonidae ; Electric Stimulation ; In Vitro Techniques ; Isometric Contraction ; drug effects ; Muscle Relaxation ; drug effects ; Muscle, Skeletal ; drug effects ; physiology

Growth Hormone (GH) is an important and powerful metabolic hormone that is secreted in a pulsatile pattern from cells in the anterior pituitary, influenced by several normal and pathophysiological conditions. Human GH was first isolated in the 1950s and human derived cadaveric GH was initially used to treat patients with GH deficiency. However, synthetic recombinant GH has been widely available since the mid-1980s and the advent of this recombinant GH boosted the abuse of GH as a doping agent. Doping with GH is a well-known problem among elite athletes and among people training at gyms, but is forbidden for both medical and ethical reasons. It is mainly the anabolic and, to some extent, the lipolytic effects of GH that is valued by its users. Even though GH's rumour as an effective ergogenic drug among athletes, the effectiveness of GH as a single doping agent has been questioned during the last few years. There is a lack of scientific evidence that GH in supraphysiological doses has additional effects on muscle exercise performance other than those obtained from optimised training and diet itself. However, there might be synergistic effects if GH is combined with, for example, anabolic steroids, and GH seems to have positive effect on collagen synthesis. Regardless of whether or not GH doping is effective, there is a need for a reliable test method to detect GH doping. Several issues have made the development of a method for detecting GH doping complicated but a method has been presented and used in the Olympics in Athens and Turin. A problem with the method used, is the short time span (24-36 hours) from the last GH administration during which the test effectively can reveal doping. Therefore, out-of-competition testing will be crucial.However, work with different approaches to develop an alternative, reliable test is ongoing.
Body Composition ; Bone and Bones ; drug effects ; Doping in Sports ; Growth Hormone ; adverse effects ; pharmacology ; physiology ; Humans ; Lipolysis ; Muscle, Skeletal ; drug effects ; physiology

BACKGROUNDSIRT3 is an important regulator in cell metabolism, and recent studies have shown that it may be involved in the pharmacological effects of metformin. However, the molecular mechanisms underlying this process are unclear.

METHODSThe effects of SIRT3 on the regulation of oxidative stress and insulin resistance in skeletal muscle were evaluated in vitro. Differentiated L6 skeletal muscle cells were treated with 750 µmol/L palmitic acid to induce insulin resistance. SIRT3 was knocked down and overexpressed in L6 cells. SIRT3, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65, c-Jun N-terminal kinase 1 (JNK1), and superoxide dismutase 2 (SOD2) were evaluated by Western blotting.

RESULTSOver expression of SIRT3 increased glucose uptake and decreased ROS production in L6-IR cells as well as in L6 cells. Knock-down of SIRT3 induced increased production of ROS while decreased glucose uptake in both L6 and L6-IR cells, and these effects were reversed by N-acetyl-L-cysteine (NAC). Metformin increased the expression of SIRT3 (1.5-fold) and SOD2 (2-fold) while down regulating NF-κB p65 (1.5-fold) and JNK1 (1.5-fold). Knockdown of SIRT3 (P < 0.05) reversed the metformin-induced decreases in NF-κB p65 and JNK1 and the metformin-induced increase in SOD2 (P < 0.05).

CONCLUSIONSUpregulated SIRT3 is involved in the pharmacological mechanism by which metformin promotes glucose uptake. Additionally, SIRT3 may function as an important regulator of oxidative stress and a new alternative approach for targeting insulin resistance-related diseases.

Animals ; Cell Line ; Insulin Resistance ; physiology ; Metformin ; pharmacology ; Muscle Fibers, Skeletal ; drug effects ; metabolism ; Oxidative Stress ; drug effects ; Rats ; Sirtuin 3 ; metabolism ; Transcription Factor RelA ; metabolism

PURPOSE: The purpose of this study was to examine the effect of anorexia and neuropathic pain induced by cisplatin on hindlimb muscles of rats. METHODS: Adult male Sprague-Dawley rats were divided into two groups, a cisplatin-treated group (n=10) and a control group (n=10). In the cisplatin-treated group, cisplatin at a dose of 2 mg/kg was injected intraperitoneally two times a week up to a cumulative dose of 20 mg/kg over 5 weeks, and in the control group saline (0.9% NaCl) was injected intraperitoneally at the same dose and duration as the cisplatin-treated group. At 34 days all rats were anesthetized, after which the soleus and plantaris muscles were dissected. Withdrawal threshold, body weight, food intake, activity, muscle weight, Type I and II fiber cross-sectional areas and myofibrillar protein content of the dissected muscles were determined. RESULTS: Compared with the control group, the cisplatin-treated group showed significant decreases (p<.05) in withdrawal threshold, activity, food intake, body weight, Type I and II fiber cross-sectional areas, myofibrillar protein content and weight of the soleus and plantaris muscles. CONCLUSION: Muscular atrophy in hindlimb occurs due to anorexia and neuropathic pain induced by the cisplatin treatment.
Animals ; *Anorexia ; Body Weight ; Cisplatin/*toxicity ; Eating ; Hindlimb ; Injections, Intraperitoneal ; Male ; Motor Activity ; Muscle Fibers, Skeletal/metabolism/pathology ; Muscle Proteins/metabolism ; Muscle, Skeletal/*drug effects/physiology ; Neuralgia/*chemically induced/pathology ; Rats ; Rats, Sprague-Dawley

Receptor proteins in both eukaryotic and prokaryotic cells often form regular lattice or array in the membrane. Recent theoretical analyses indicate that such arrays may provide a novel mechanism for receptor signaling regulation in cells. The functional coupling between neighboring receptors could improve the signaling performance. The ryanodine receptors (RyR)/calcium release channels usually form 2-D regular lattice in the endoplasmic/sarcoplasmic reticulum membranes. Thus, RyR is a potentially good model to study the function of receptor 2-D array. In this article, we briefly review recent progresses in this research field, including RyR-RyR interaction, RyR array's function and working mechanisms. The investigations performed by new methods in our laboratory are summarized. We demonstrate that the RyR-RyR interaction is modulated by the functional states of RyRs. Accordingly, the mechanism of "dynamic coupling" of RyR array is proposed. Its possible role in RyR-mediated Ca(2+) release is discussed.
Animals ; Calcium ; metabolism ; Cations ; Humans ; Muscle, Skeletal ; drug effects ; metabolism ; Receptor Cross-Talk ; physiology ; Ryanodine Receptor Calcium Release Channel ; physiology ; Sarcoplasmic Reticulum ; metabolism

The aim of the present study was to investigate the effect of carnitine on function of respiratory chain and metabolism of oxygen radical in mitochondria of skeletal muscle after exhaustive running in training rats. Forty male Wistar rats were randomly divided into 4 groups (n = 10): control, carnitine, training and training + carnitine groups. The training and training + carnitine groups received 6-week treadmill training, whereas carnitine and training + carnitine groups were administered intragastrically with carnitine (300 mg/kg per day, 6 d/week) for 6 weeks. After exhaustive running, all the rats from 4 groups were sacrificed to obtain quadriceps muscles samples, and muscle mitochondria were extracted by differential centrifugation. Spectrophotometric analysis was used to evaluate activities of respiratory chain complexes (RCC) I-IV, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and the content of malondialdehyde (MDA) in the skeletal muscle mitochondria. The results showed that, compared with the control group, the carnitine group exhibited increased RCCI and RCCIII activities (P < 0.05), the training + carnitine group exhibited increased RCCI, RCCIII and RCCIV activities (P < 0.05 or 0.01). Moreover, RCCIII activity in the training + carnitine group was higher than that in training group (P < 0.05). Compared with the control group, the carnitine, training and training + carnitine groups showed increased SOD activities ( P < 0.01), the carnitine and training + carnitine groups showed increased GSH-Px activities ( P < 0.01), the carnitine, training and training + carnitine groups showed increased MDA contents (P < 0.05 or 0.01). The SOD and GSH-Px activities in training + carnitine group were higher than those in training group (P < 0.01), and the MDA level in the training + carnitine group was higher than that in the carnitine and training groups (P < 0.01). These results suggest that training and carnitine can increase function of respiratory chain, antioxidation and lipid peroxidation tolerance capacity in skeletal muscle mitochondria, and the improving effects of training and carnitine are synergistic.
Animals ; Antioxidants ; metabolism ; Carnitine ; pharmacology ; Electron Transport ; Glutathione Peroxidase ; metabolism ; Male ; Malondialdehyde ; metabolism ; Mitochondria, Muscle ; drug effects ; physiology ; Muscle, Skeletal ; drug effects ; physiology ; Physical Conditioning, Animal ; Rats ; Rats, Wistar ; Reactive Oxygen Species ; metabolism ; Running ; Superoxide Dismutase ; metabolism

PURPOSE: The purpose of this study was to examine the effects of daily exercise before steroid treatment on mass, the type I and II fiber cross-sectional area, and myofibrillar protein content of hindlimb muscles in a rat model. METHOD: Adult male Sprague-Dawley rats were randomly assigned to one of three groups: a control group(n=10) that had a normal saline injection for 7days, a steroid group(n=10) that had a steroid injection for 7days, and an exercise-steroid group(n=10) that ran on the treadmill for 7days before a steroid treatment. Body weight and food intake were measured every day. At 15 days all rats were anesthetized and the soleus, plantaris and gastrocnemius muscles were dissected. RESULT: The exercise-steroid group showed significant increases as compared with the steroid group in body weight, muscle weight of the soleus and gastrocnemius, type II muscle fiber cross-sectional area of plantaris, and myofibrillar protein content of the soleus, plantaris, and gastrocnemius. As compared with the control group, the steroid group showed significant decreases in body weight and diet intake, muscle weight, the type II fiber cross-sectional area and myofibrillar protein content of the soleus, plantaris, and gastrocnemius muscles. CONCLUSION: Daily exercise before steroid treatment attenuates hindlimb muscle atrophy, with type II muscle changes more apparent than type I muscle changes.
Animals ; Body Weight ; Combined Modality Therapy ; Dexamethasone/*therapeutic use ; Disease Models, Animal ; *Exercise Therapy ; Hindlimb ; Male ; Muscle Contraction/drug effects ; Muscle Fibers, Skeletal/*drug effects/physiology ; Muscle, Skeletal/*drug effects/physiology ; Muscular Atrophy/etiology/pathology/*therapy ; Organ Size ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study characteristics of energy metabolism in the skeletal muscle of rats with postoperative fatigue syndrome (POFS) and the interventional effect of ginsenoside Rb1.

METHODWe chose resection of 70% of the "middle" small intestine as the rat model for POFS. Ninety-six adult male SPF SD rats were randomly divided into the control group, the model group, and the ginsenoside Rb1-treated group by body weight. And then, each group was further randomly divided into four subgroups, according to different postoperative investigated time points, such as postoperative day 1, postoperative day 3, postoperative day 7 and postoperative day 10. So the animals were divided into twelve subgroups (n = 8 in each subgroup). Rats of the control group and the model group were injected intraperitoneally with saline at the dose of 10 mL x kg(-1) one hour before the operation and once a day during the postoperative days. Rats of the ginsenoside Rb1-treated group were administered 10 mg x kg(-1) ginsenoside Rb1 by the same method. The skeletal muscles were sampled on postoperative day 1, 3, 7 and 10. The contents of ATP, ADP, AMP in skeletal muscles were determined by HPLC, and the activities of Na(+)-K(+)-ATPase and Ca(2+)-ATPase were investigated by colorimetry.

RESULTCompared with the control group, the content of ATP in skeletal muscle of rats of the model group decreased significantly on postoperative day 3 (P < 0.05), while the content of ADP significantly increased on postoperative day 7 and 10 (P < 0.05). The activity of Na(+)-K(+)-AT-Pase decreased on postoperative day 3 and 7 (P < 0.05), and the activity of Ca(2+)-ATPase decreased on postoperative day 7. After supplement of ginsenoside Rb1, on the investigated time points, all the negative changes of the indicators discovered above were significantly adjusted (P < 0.05) in rats of the ginsenoside Rb1-treated group, while no significant differences were investigated.

CONCLUSIONDuring a certain period of postoperative time, the activity of energy metabolism is depressed in the skeletal muscle of rats with POFS, but it can be improved by supplement of ginsenoside Rb1.

Animals ; Calcium-Transporting ATPases ; physiology ; Energy Metabolism ; drug effects ; Fatigue ; drug therapy ; metabolism ; Ginsenosides ; pharmacology ; therapeutic use ; Male ; Muscle, Skeletal ; metabolism ; Postoperative Complications ; drug therapy ; metabolism ; Rats ; Rats, Sprague-Dawley ; Sodium-Potassium-Exchanging ATPase ; physiology ; Syndrome

OBJECTIVETo observe the effect of the postpone in skeletal muscle aging process of D-galactose rats by weight training and soy polypeptide supplement in 6 weeks, and discuss the initial mechanism.

METHODSixty male SD rats (three month old)were randomly assigned: 6 week control (C6,) and 6 week model (M6) 6 for each group, 12 week model (M12), big load (B12), small load (S12), peptide (P12), peptide + big load (PB12) and peptide + small load group (PS12) 8 for each group, eight fourteen month rats were taken in the natural aging group. The rats were killed by the end of 6th week and 12th week, tested the indicators.

RESULTCompare with group C6, the indicators in group M6 showed aging in different levels; Compare with group M12, weight training or soy polypeptide supplement in all intervention groups could increase the content of skeletal muscle superoxide dismutase (SOD), SOD/MDA, the serum growth hormone(GH), insulin-like growth factor-1 (IGF-I)and skeletal muscle IGF-I mRNA, decreased the malondialdehyde (MDA) content of skeletal muscle, and they had notable interaction.

CONCLUSIONRat skeletal muscle aging model can be copied successfully by D-galactose hypodermic, and go on with 6-week weight training or soy polypeptide supplement, they can postpone the skeletal muscle aging process of D-galactose rats, and the two interference way united can have more obvious effect. Its preliminary mechanism may be related to the reduction of skeletal muscle oxidative stress and lipid peroxidation, the correction of hormones and related factors metabolic disorders, the elevation of skeletal muscle IGF-I mRNA expression and so on.

Aging ; physiology ; Animals ; Galactose ; Growth Hormone ; blood ; Insulin-Like Growth Factor I ; metabolism ; Male ; Malondialdehyde ; metabolism ; Muscle, Skeletal ; drug effects ; physiology ; Physical Conditioning, Animal ; physiology ; Rats ; Rats, Sprague-Dawley ; Soybean Proteins ; pharmacology ; Soybeans ; chemistry ; Superoxide Dismutase ; metabolism