Abstract 237: Antioxidant and Ryanodine Receptor Stabilizing Therapy Prevent Statin-Induced Contractile Dysfunction in a Tissue-Engineered Skeletal Muscle Model

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Malte Tiburcy ◽  
Guenther Engel ◽  
Sonka J Sanders ◽  
Wolfram H Zimmermann
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Molecular Mechanisms ◽  
Early Stage ◽  
Muscle Model ◽  
Contractile Dysfunction ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Force Reduction ◽  
Muscle Toxicity

Rationale: Skeletal muscle toxicity of HMG-CoA-reductase inhibitors (statins) ranges from reversible myalgia to irreversible rhabdomyolysis. The underlying molecular mechanisms are not well defined. Tissue engineering models may help to gain insight into these clinically limiting pathologies. Objective: Here we aimed to model a phenotype of reversible myalgia in vitro to decipher mechanisms that contribute to the early stage of statin toxicity. Methods and Results: Engineered skeletal muscle (ESM) was generated from rat myoblasts, matrigel, and collagen. Isometrically suspended ESM developed 1.2±0.1 mN force under tetanic field stimulation (80 Hz; 200 mA; n=25). Exposure of ESM to statins for 5 days resulted in a loss of force and increased fatiguability in a concentration dependent manner. Cerivastatin was identified as the most potent statin with respect to muscle toxicity with a TC50 (=50% force reduction) of 0.02 µmol/L (n=25/group). Interestingly, at low cerivastatin concentration (0.01 µmol/L) contractile force of ESM was impaired without obvious signs for structural muscle damage (sarcomeric actin content, CK activity unchanged, n=4). Importantly, ESM dysfunction was fully reversible if challenged with TC50 statin concentrations (n=12-14/group). We reasoned that contractile dysfunction with increased fatiguability resulted from calcium leak via the ryanodine receptor. To test this hypothesis we co-administered S107 and observed a concentration-dependent inhibition of statin-induced force reduction (n=12) and calpain activitiy (a calcium-dependent protease, n=4-6). We further argued that RYR destabilization may have been caused by reactive nitrogen (RNS) and/or reactive oxygen species (ROS). Interestingly, the antioxidant N-acetyl cysteine (1 mmol/L, n=3/group), but not L-NAME (10 mmol/L; NO-synthase inhibition, n=6-12/group) prevented contractile dysfunction. Conclusion: We utilized a novel tissue engineered skeletal muscle model to decipher mechanisms of statin-induced muscle toxicity and provide evidence for a central role of ryanodine receptor leak, possibly caused by oxidative damage. Our data suggest that antioxidant and RYR-stabilizing approaches may be useful in counteracting statin myopathy.

scholarly journals Interactions of Dichlorodiphenyltrichloroethane (DDT) and Dichlorodiphenyldichloroethylene (DDE) With Skeletal Muscle Ryanodine Receptor Type 1

2019 ◽  
Vol 170 (2) ◽  
pp. 509-524
Author(s):  
Kim M Truong ◽  
Gennady Cherednichenko ◽  
Isaac N Pessah
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptor ◽  
Membrane Vesicles ◽  
Receptor Type ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Voltage Gated Sodium Channels ◽  
Muscle Health ◽  
Living Organisms

Abstract Dichlorodiphenyltrichloroethane (DDT) and its metabolite dichlorodiphenyldichloroethylene (DDE) are ubiquitous in the environment and detected in tissues of living organisms. Although DDT owes its insecticidal activity to impeding closure of voltage-gated sodium channels, it mediates toxicity in mammals by acting as an endocrine disruptor (ED). Numerous studies demonstrate DDT/DDE to be EDs, but studies examining muscle-specific effects mediated by nonhormonal receptors in mammals are lacking. Therefore, we investigated whether o,p′-DDT, p,p′-DDT, o,p′-DDE, and p,p′-DDE (DDx, collectively) alter the function of ryanodine receptor type 1 (RyR1), a protein critical for skeletal muscle excitation-contraction coupling and muscle health. DDx (0.01–10 µM) elicited concentration-dependent increases in [3H]ryanodine ([3H]Ry) binding to RyR1 with o,p′-DDE showing highest potency and efficacy. DDx also showed sex differences in [3H]Ry-binding efficacy toward RyR1, where [3H]Ry-binding in female muscle preparations was greater than male counterparts. Measurements of Ca2+ transport across sarcoplasmic reticulum (SR) membrane vesicles further confirmed DDx can selectively engage with RyR1 to cause Ca2+ efflux from SR stores. DDx also disrupts RyR1-signaling in HEK293T cells stably expressing RyR1 (HEK-RyR1). Pretreatment with DDx (0.1–10 µM) for 100 s, 12 h, or 24 h significantly sensitized Ca2+-efflux triggered by RyR agonist caffeine in a concentration-dependent manner. o,p′-DDE (24 h; 1 µM) significantly increased Ca2+-transient amplitude from electrically stimulated mouse myotubes compared with control and displayed abnormal fatigability. In conclusion, our study demonstrates DDx can directly interact and modulate RyR1 conformation, thereby altering SR Ca2+-dynamics and sensitize RyR1-expressing cells to RyR1 activators, which may ultimately contribute to long-term impairments in muscle health.

Two novel types of calcium release from skeletal sarcoplasmic reticulum by phosphatidylinositol 4,5-bisphosphate

1999 ◽  
Vol 77 (4) ◽  
pp. 276-285 ◽  
Author(s):  
Yasushi Ohizumi ◽  
Yutaka Hirata ◽  
Atsuko Suzuki ◽  
Masaki Kobayashi
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Ryanodine Receptor ◽  
Calcium Release ◽  
Ruthenium Red ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Steady Level ◽  
Ryanodine Receptor 1 ◽  
Sarcoplasmic Reticulum Calcium

In both the heavy and light fractions of fragmented sarcoplasmic reticulum (SR) vesicles from the fast skeletal muscle, about 27 min after beginning the active Ca2+ uptake, the extravesicular Ca2+ concentration suddenly increased to reach a steady level (delayed Ca2+ release). Phosphatidylinositol 4,5-bisphosphate (PIP2) not only shortened the time to delayed Ca2+ release but also induced prompt Ca2+ release from the heavy fraction of SR. Delayed Ca2+ release and prompt Ca2+ release stimulated by 100 µM PIP2 were not modified by ruthenium red. PIP2 (>0.1 µM) markedly accelerated the rate of 45Ca2+ efflux from SR vesicles in a concentration-dependent manner. The PIP2-induced 45Ca2+ efflux was potentiated by ruthenium red but profoundly inhibited by La3+. The concentration-response curve for Ca2+ or Mg2+ in PIP2-induced 45Ca2+ release was clearly different from that in the Ca2+-induced Ca2+ release. PIP2 caused a concentration-dependent increase in Ca2+ release from SR of chemically skinned fibers from skeletal muscle. Furthermore, [3H]ryanodine or [3H]methyl-7-bromoeudistomin D (MBED) binding to SR was increased by PIP2 in a concentration-dependent manner. These observations present the first evidence that PIP2 most likely activates two types of SR Ca2+ release channels whose properties are entirely different from those of Ca2+-induced Ca2+ release channels (the ryanodine receptor 1).Key words: phosphatidylinositol 4,5-bisphosphate, sarcoplasmic reticulum, calcium release, ryanodine receptor, ryanodine.

The Anti-Atherogenic Properties of Sesamin are Mediated via Improved Macrophage Cholesterol Efflux Through PPARγ1-LXRα and MAPK Signaling

2014 ◽  
Vol 84 (1-2) ◽  
pp. 79-91 ◽  
Author(s):  
Amin F. Majdalawieh ◽  
Hyo-Sung Ro
Keyword(s):  
Cholesterol Efflux ◽  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Foam Cell ◽  
Mapk Signaling ◽  
Luciferase Reporter ◽  
Foam Cell Formation ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Macrophage Cholesterol Efflux

Background: Foam cell formation resulting from disrupted macrophage cholesterol efflux, which is triggered by PPARγ1 and LXRα, is a hallmark of atherosclerosis. Sesamin and sesame oil exert anti-atherogenic effects in vivo. However, the exact molecular mechanisms underlying such effects are not fully understood. Aim: This study examines the potential effects of sesamin (0, 25, 50, 75, 100 μM) on PPARγ1 and LXRα expression and transcriptional activity as well as macrophage cholesterol efflux. Methods: PPARγ1 and LXRα expression and transcriptional activity are assessed by luciferase reporter assays. Macrophage cholesterol efflux is evaluated by ApoAI-specific cholesterol efflux assays. Results: The 50 μM, 75 μM, and 100 μM concentrations of sesamin up-regulated the expression of PPARγ1 (p< 0.001, p < 0.001, p < 0.001, respectively) and LXRα (p = 0.002, p < 0.001, p < 0.001, respectively) in a concentration-dependent manner. Moreover, 75 μM and 100 μM concentrations of sesamin led to 5.2-fold (p < 0.001) and 6.0-fold (p<0.001) increases in PPAR transcriptional activity and 3.9-fold (p< 0.001) and 4.2-fold (p < 0.001) increases in LXR transcriptional activity, respectively, in a concentration- and time-dependent manner via MAPK signaling. Consistently, 50 μM, 75 μM, and 100 μM concentrations of sesamin improved macrophage cholesterol efflux by 2.7-fold (p < 0.001), 4.2-fold (p < 0.001), and 4.2-fold (p < 0.001), respectively, via MAPK signaling. Conclusion: Our findings shed light on the molecular mechanism(s) underlying sesamin’s anti-atherogenic effects, which seem to be due, at least in part, to its ability to up-regulate PPARγ1 and LXRα expression and transcriptional activity, improving macrophage cholesterol efflux. We anticipate that sesamin may be used as a therapeutic agent for treating atherosclerosis.

Methanol Extract of Mongolian Iris bungei Maxim. Stimulates 3T3-L1 Adipocyte Differentiation

2021 ◽  
Vol 21 (7) ◽  
pp. 3943-3949
Author(s):  
Jaegoo Yeon ◽  
Sung-Suk Suh ◽  
Ui-Joung Youn ◽  
Badamtsetseg Bazarragchaa ◽  
Ganbold Enebish ◽  
...  
Keyword(s):  
Bacterial Infections ◽  
Fatty Acid Synthase ◽  
Molecular Mechanisms ◽  
Adipocyte Differentiation ◽  
Methanol Extract ◽  
Regulatory Element ◽  
Peroxisome Proliferator ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Peroxisome Proliferator Activated Receptor

Iris bungei Maxim. (IB), which is native to China and Mongolia, is used as a traditional medicine for conditions such as inflammation, cancer, and bacterial infections. However, the effects of Iris bungei Maxim. on adipocyte differentiation have not been studied. In the present study, we first demonstrated the molecular mechanisms underlying the adipogenic activity of the methanol extract of Mongolian I. bungei Maxim. (IB). IB significantly enhanced intracellular lipid accumulation and adipocyte differentiation in 3T3-L1 preadipocytes in a concentration-dependent manner. Moreover, IB markedly stimulated the expression of genes related to adipogenesis such as peroxisome proliferator-activated receptor γ, adiponectin, and aP2. In addition, we also observed that IB induces lipogenic genes such as fatty acid synthase, sterol regulatory element binding protein 1c, stearoyl-CoA desaturase, and acetyl-CoA carboxylase. Interestingly IB regulated adipocyte differentiation in both the early and middle stages. Taken together, these adipogenic and lipogenic effects of IB suggest its efficacy for the prevention and/or treatment of type 2 diabetes.

scholarly journals Betulinic Acid Suppresses Ovarian Cancer Cell Proliferation through Induction of Apoptosis

Biomolecules ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 257 ◽  
Author(s):  
Dahae Lee ◽  
Seoung Rak Lee ◽  
Ki Sung Kang ◽  
Yuri Ko ◽  
Changhyun Pang ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Cancer Cell ◽  
Betulinic Acid ◽  
Molecular Mechanisms ◽  
Underlying Mechanism ◽  
Nuclear Staining ◽  
Dependent Manner ◽  
Meoh Extract ◽  
Concentration Dependent Manner ◽  
Induction Of Apoptosis

Ovarian cancer is one of the leading causes of cancer deaths worldwide in women, and the most malignant cancer among the different gynecological cancers. In this study, we explored potentially anticancer compounds from Cornus walteri (Cornaceae), the MeOH extract of which has been reported to show considerable cytotoxicity against several cancer cell lines. Phytochemical investigations of the MeOH extract of the stem and stem bark of C. walteri by extensive application of chromatographic techniques resulted in the isolation of 14 compounds (1–14). The isolated compounds were evaluated for inhibitory effects on the viability of A2780 human ovarian carcinoma cells and the underlying molecular mechanisms were investigated. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was employed to assess the anticancer effects of compounds 1–14 on A2780 cells, which showed that compound 11 (betulinic acid) reduced the viability of these cells in a concentration-dependent manner and had an half maximal (50%) inhibitory concentration (IC50) of 44.47 μM at 24 h. Nuclear staining and image-based cytometric assay were carried out to detect the induction of apoptosis by betulinic acid. Betulinic acid significantly increased the condensation of nuclei and the percentage of apoptotic cells in a concentration-dependent manner in A2780 cells. Western blot analysis was performed to investigate the underlying mechanism of apoptosis. The results indicated that the expression levels of cleaved caspase-8, -3, -9, and Bax were increased in A2780 cells treated with betulinic acid, whereas those of Bcl-2 were decreased. Thus, we provide the experimental evidence that betulinic acid can induce apoptosis in A2780 cells through both mitochondria-dependent and -independent pathways and suggest the potential use of betulinic acid in the development of novel chemotherapeutics for ovarian cancer therapy.

scholarly journals MON-647 Mechanisms of Insulin Resistance in Skeletal Muscle in Women with PCOS

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Alba Moreno-Asso ◽  
Luke C McIlvenna ◽  
Rhiannon K Patten ◽  
Andrew J McAinch ◽  
Raymond J Rodgers ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Reproductive Age ◽  
Whole Body ◽  
Dependent Manner ◽  
Cultured Myotubes ◽  
Tgfβ Superfamily

Abstract Polycystic ovary syndrome (PCOS) is the most common female endocrine disorder affecting metabolic, reproductive and mental health of 8-13% of reproductive-age women. Insulin resistance (IR) appears to underpin the pathophysiology of PCOS and is present in approximately 85% of women with PCOS. This underlying IR has been identified as unique from, but synergistic with, obesity-induced IR (1). Skeletal muscle accounts for up to 85% of whole body insulin-stimulated glucose uptake, however, in PCOS this is reduced about 27% when assessed by hyperinsulinemic euglycemic clamp (2). Interestingly, this reduced insulin-stimulated glucose uptake observed in skeletal muscle tissue is not retained in cultured myotubes (3), suggesting that environmental factors may play a role in this PCOS-specific IR. Yet, the molecular mechanisms regulating IR remain unclear (4). Previous work suggested that Transforming Growth Factor Beta (TGFβ) superfamily ligands may be involved in the metabolic morbidity associated with PCOS (5). In this study, we investigated the effects of TGFβ1 (1, 5ng/ml), and the Anti-Müllerian hormone (AMH; 5, 10, 30ng/ml), a novel TGFβ superfamily ligand elevated in women with PCOS, as causal factors of IR in cultured myotubes from women with PCOS (n=10) and healthy controls (n=10). AMH negatively affected glucose uptake and insulin signalling increasing p-IRS1 (ser312) in a dose-dependent manner in myotubes from both women with and without PCOS. AMH did not appear to activate the canonical TGFβ/BMP signalling pathway. Conversely, TGFβ1 had an opposite effect in both PCOS and control myotubes cultures, decreasing phosphorylation of IRS1 (ser312) and enhancing glucose uptake via Smad2/3 signalling. In conclusion, these results suggest that AMH may play a role in skeletal muscle IR observed in PCOS, however, further research is required to elucidate its mechanisms of action and broader impact in this syndrome. References: (1) Stepto et al. Hum Reprod 2013 Mar;28(3):777-784. (2) Cassar et al. Hum Reprod 2016 Nov;31(11):2619-2631. (3) Corbould et al., Am J Physiol-Endoc 2005 May;88(5):E1047-54. (4) Stepto et al. J Clin Endocrinol Metab, 2019 Nov 1;104(11):5372-5381. (5) Raja-Khan et al. Reprod Sci 2014 Jan;21(1):20-31.

Vascular Protective Effects of Xanthotoxin and Its Action Mechanism in Rat Aorta and Human Vascular Endothelial Cells

2020 ◽  
Vol 57 (6) ◽  
pp. 313-324
Author(s):  
Li-Hua Cao ◽  
Ho Sub Lee ◽  
Zhe-Shan Quan ◽  
Yun Jung Lee ◽  
Yu Jin
Keyword(s):  
Endothelial Cells ◽  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Molecular Mechanisms ◽  
Umbilical Vein ◽  
Neuroprotective Effect ◽  
Intercellular Adhesion Molecule ◽  
Dependent Manner ◽  
Protective Effects ◽  
Concentration Dependent Manner

<b><i>Objective:</i></b> Xanthotoxin (XAT) is a linear furanocoumarin mainly extracted from the plants <i>Ammi majus</i> L. XAT has been reported the apoptosis of tumor cells, anti-convulsant, neuroprotective effect, antioxidative activity, and vasorelaxant effects. This study aimed to investigate the vascular protective effects and underlying molecular mechanisms of XAT. <b><i>Methods:</i></b> XAT’s activity was studied in rat thoracic aortas, isolated with aortic rings, and human umbilical vein endothelial cells (HUVECs). <b><i>Results:</i></b> XAT induced endothelium-dependent vasodilation in a concentration-dependent manner in the isolated rat thoracic aortas. Removal of endothelium or pretreatment of aortic rings with L-NAME, 1<i>H</i>-[1,2,4]-oxadiazolo-[4,3-<i>a</i>]-quinoxalin-1-one, and wortmannin significantly inhibited XAT-induced relaxation. In addition, treatment with thapsigargin, 2-aminoethyl diphenylborinate, Gd<sup>3+</sup>, and 4-aminopyridine markedly attenuated the XAT-induced vasorelaxation. XAT increased nitric oxide production and Akt- endothelial NOS (eNOS) phosphorylation in HUVECs. Moreover, XAT attenuated the expression of TNF-α-induced cell adhesion molecules such as intercellular adhesion molecule, vascular cell adhesion molecule-1, and E-selectin. However, this effect was attenuated by the eNOS inhibitors L-NAME and asymmetric dimethylarginine. <b><i>Conclusions:</i></b> This study suggests that XAT induces vasorelaxation through the Akt-eNOS-cGMP pathway by activating the K<sub>V</sub> channel and inhibiting the L-type Ca<sup>2+</sup> channel. Furthermore, XAT exerts an inhibitory effect on vascular inflammation, which is correlated with the observed vascular protective effects.

cADP-ribose releases Ca2+ from cardiac sarcoplasmic reticulum independently of ryanodine receptor

1997 ◽  
Vol 273 (3) ◽  
pp. H1082-H1089 ◽  
Author(s):  
P. Lahouratate ◽  
J. Guibert ◽  
J. F. Faivre
Keyword(s):  
Endoplasmic Reticulum ◽  
Sarcoplasmic Reticulum ◽  
Ryanodine Receptor ◽  
Sea Urchin ◽  
Calcium Release ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Consistent Effect ◽  
Cyclic Adp Ribose

Cyclic ADP-ribose (cADPR), an endogenous metabolite of beta-NAD+, activates Ca2+ release from endoplasmic reticulum in sea urchin eggs via the ryanodine receptor (RyR) pathway. A similar role has been proposed in cardiac sarcoplasmic reticulum (SR), although this remains controversial. We therefore investigated the ability of cADPR to induce Ca2+ release from canine cardiac SR microsomes using fluo 3 to monitor extravesicular Ca2+ concentration. We found that cADPR induced Ca2+ release in a concentration-dependent manner, whereas neither its precursor, NAD+, nor its metabolite, ADP-ribose, elicited a consistent effect. In addition, an additive effect on calcium release between cADPR and 9-Me-7-Br-eudistomin-D (MBED), an activator of RyR, was found as well as no cross-desensitization between cADPR and MBED. Specific blockers of the RyR did not abolish the cADPR-induced Ca2+ release. These results provide evidence for cADPR-induced Ca2+ release from dog cardiac SR via a novel mechanism which is independent of RyR activation.

scholarly journals Suppression of the TGF-β pathway by a macrolide antibiotic decreases fibrotic responses by ocular fibroblasts in vitro

2020 ◽  
Vol 7 (9) ◽  
pp. 200441
Author(s):  
Thomas Stahnke ◽  
Beata Gajda-Deryło ◽  
Anselm G. Jünemann ◽  
Oliver Stachs ◽  
Katharina A. Sterenczak ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Macrolide Antibiotic ◽  
Drug Repositioning ◽  
Dependent Manner ◽  
Glaucoma Filtration Surgery ◽  
Concentration Dependent Manner ◽  
Device Implantation

To elucidate and to inhibit post-surgical fibrotic processes after trabeculectomy in glaucoma therapy, we measured gene expression in a fibrotic cell culture model, based on transforming growth factor TGF-β induction in primary human tenon fibroblasts (hTFs), and used Connectivity Map (CMap) data for drug repositioning. We found that specific molecular mechanisms behind fibrosis are the upregulation of actins, the downregulation of CD34, and the upregulation of inflammatory cytokines such as IL6, IL11 and BMP6 . The macrolide antibiotic Josamycin (JM) reverses these molecular mechanisms according to data from the CMap, and we thus tested JM as an inhibitor of fibrosis. JM was first tested for its toxic effects on hTFs, where it showed no influence on cell viability, but inhibited hTF proliferation in a concentration-dependent manner. We then demonstrated that JM suppresses the synthesis of extracellular matrix (ECM) components. In hTFs stimulated with TGF-β1, JM specifically inhibited α-smooth muslce actin expression, suggesting that it inhibits the transformation of fibroblasts into fibrotic myofibroblasts. In addition, a decrease of components of the ECM such as fibronectin, which is involved in in vivo scarring, was observed. We conclude that JM may be a promising candidate for the treatment of fibrosis after glaucoma filtration surgery or drainage device implantation in vivo .

Differential Effects of Sevoflurane, Isoflurane, and Halothane on Ca (2+) Release from the Sarcoplasmic Reticulum of Skeletal Muscle 

1999 ◽  
Vol 91 (1) ◽  
pp. 179-186 ◽  
Author(s):  
Gudrun Kunst ◽  
Bernhard M. Graf ◽  
Rupert Schreiner ◽  
Eike Martin ◽  
Rainer H. A. Fink
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Muscle Fibers ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Maximal Force ◽  
Skinned Muscle ◽  
Skeletal Muscle Fibers ◽  
Force Relation ◽  
The Individual

Background Although malignant hyperthermia after application of sevoflurane has been reported, little is known about its action on intracellular calcium homeostasis of skeletal muscle. The authors compared the effect of sevoflurane with that of isoflurane and halothane on Ca2+ release of mammalian sarcoplasmic reticulum and applied a novel method to quantify Ca2+ turnover in permeabilized skeletal muscle fibers. Methods Liquid sevoflurane, isoflurane, and halothane at 0.6 mM, 3.5 mM, and 7.6 mm were diluted either in weakly calcium buffered solutions with no added Ca2+ (to monitor Ca2+ release) or in strongly Ca2+ buffered solutions with [Ca2+] values between 3 nM and 24.9 microm for [Ca+]-force relations. Measurements were taken on single saponin skinned muscle fiber preparations of BALB/c mice. Individual [Ca2+]force relations were characterized by the Ca2+ concentration at half-maximal force that indicates the sensitivity of the contractile proteins and by the steepness. Each force transient was transformed directly into a Ca2+ transient with respect to the individual [Ca2+]-force relation of the fiber. Results At 0.6 mM, single force transients induced by sevoflurane were lower compared with equimolar concentrations of isoflurane and halothane (P &lt; 0.05). Similarly, calculated peak Ca2+ transients of sevoflurane were lower than those induced by equimolar halothane (P &lt; 0.05). The Ca2+ concentrations at half maximal force were decreased after the addition of sevoflurane, isoflurane, and halothane in a concentration-dependent manner (P &lt; 0.05). Conclusion Whereas sevoflurane, isoflurane, and halothane similarly increase the Ca2+ sensitivity of the contractile apparatus in skeletal muscle fibers, 0.6 mM sevoflurane induces smaller Ca2+ releases from the sarcoplasmic reticulum than does equimolar halothane.

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