Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.4.1 (myosin ATPase)
1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies in cat, rat, and swine have implicated fiber type as influencing the halothane and caffeine contracture test used to diagnose malignant hyperthermia (MH). The authors performed fiber type analysis using myosin ATPase stains on 31 fascicles of skeletal muscle from nine patients following contracture testing. There was no significant difference in fiber type composition between fascicles from MH negative (n = 5) and MH positive (n = 4) patients. Furthermore, examining each of the 31 fascicles, the authors found no correlation (P greater than .05) of contracture magnitude with percentage of either Type I or Type II fibers using the Pearson Product-Moment correlation calculation. The authors conclude that fiber type composition does not influence contracture test results in human biopsies.
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PMID:No relationship between fiber type and halothane contracture test results in malignant hyperthermia. 244 Mar 53

Heat production (measured myothermically), force development and isomyosin distribution were measured in left ventricular papillary muscles from adult male rats in three thyroid states: hyperthyroid (T3), euthyroid (C) and hypothyroid (Tx). Rats were rendered hyperthyroid by daily injections of tri-iodothyronine and hypothyroid by radioisotopic thyroidectomy. Papillary muscle performance was measured both for trains of isometric twitches and for brief (2 s) tetani achieved by increasing the Ca2+ concentration and adding caffeine to the bathing solution. Resting metabolic rate was uninfluenced by thyroid state. Heat-stress relations were determined for both twitches and tetani by altering muscle length. Tx muscles showed an elevated stress-independent or activation heat (intercept of the heat-stress relation), a depressed stress-dependent heat (slope of the heat-stress relation), and greatly enhanced peak twitch and tetanic (Smax) stresses. When normalized for Smax, the maximal rates of tetanic stress development and heat production were depressed in the Tx group. In the T3 group, only the normalized maximal rate of tetanic stress development was significantly increased. The lack of significant effects on other mechanical and energetic parameters probably reflects an under-dosing of animals in this tri-iodothyronine-treated group, an interpretation supported by the modest change in isomyosin distribution resulting from the treatment regimen used. Separate isomyosin analyses of papillary muscles and their associated ventricles yielded excellent correlation demonstrating the suitability of papillary muscles as a model of ventricular wall tissue. By experimentally manipulating the thyroid state, the distribution of the three ventricular isomyosins were correspondingly altered with a shift toward a greater and lesser proportion of high activity myosin ATPase in the hyperthyroid and hypothyroid groups respectively. The average proportions of the myosin heavy chain associated with high actin-activated myosin ATPase were 86, 74 and 6% for groups T3, C and Tx respectively. The measured changes in papillary muscle energetics correlate well with these thyroid-induced changes in isomyosin distribution and can be explained in terms of altered crossbridge dynamics.
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PMID:Energetic consequences of thyroid-modulated shifts in ventricular isomyosin distribution in the rat. 707 27

We investigated the mechanism by which caffeine influences myofilament responsiveness to Ca2+ by measuring isometric force, Ca2+ binding, and ATPase activity of dog cardiac myofilament proteins. Caffeine (20 mM) increased submaximal and depressed maximal force in skinned fiber bundles. Although the Ca2+ sensitivity of myofilament activity was increased by caffeine, there was no effect on Ca2+ binding to troponin C (TnC) in skinned fiber bundles. To determine if caffeine altered actin-myosin interaction or affected myosin directly, myofibrillar, actomyosin, and myosin ATPase activities were measured. Maximal Ca(2+)-activated myofibrillar Mg(2+)-ATPase activity was depressed by 20 mM caffeine, whereas submaximal Mg(2+)-ATPase activities were not changed. Actomyosin Mg(2+)-ATPase activity was significantly depressed by caffeine concentrations > or = 15 mM. Myosin Ca(2+)-ATPase activity was depressed by caffeine, whereas Mg(2+)-ATPase and K(EDTA)-ATPase activities were not affected. These data suggest that caffeine affects myofilament function via a mechanism that is independent of TnC-Ca2+ binding but that may involve direct effects on actin-cross-bridge interaction.
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PMID:Caffeine alters cardiac myofilament activity and regulation independently of Ca2+ binding to troponin C. 761 52

The addition of 15 mM caffeine to saponin-skinned human muscle fibers from M. vastus lateralis caused in the presence of 2 mM ATP an approx. 2-fold stimulation of respiration with glutamate+malate. This effect can be abolished by either the addition of the Ca2+ chelator EGTA, the inhibitor of Ca2+ transport Ruthenium red and the inhibitor of the myosin ATPase vanadate. The caffeine concentration dependency of respiration of fibers coincided with the caffeine-caused stimulation of myosin ATPase activity. The activation of oxidative phosphorylation in saponin-skinned human muscle fibers by caffeine can be explained by a stimulation of myosin ATPase caused by Ca2+ release from sarcoplasmic reticulum.
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PMID:Mitochondrial oxidative phosphorylation in saponin-skinned human muscle fibers is stimulated by caffeine. 849 38

Several works have shown the importance of the creatine kinase (CK) system for cardiac energetics and Ca2+ homeostasis. Nevertheless, CK-deficient mice have cardiac function close to normal, at least under conditions of low or moderate workload. To characterize possible adaptive changes of the sarcoplasmic reticulum (SR) and potential role of glycolytic support in cardiac contractility we used the skinned fibre technique to study properties of the SR and myofibrils, in control and muscle-type homodimer (MM-/mitochondrial-CK)-deficient mice. In control fibres, SR Ca2+ loading with ATP and phosphocreatine (solution PL) was significantly better than loading with ATP alone (solution AL), as determined by analysis of caffeine-induced tension transients. Loading in the presence of ATP and glycolytic intermediates (solution GL) was not significantly different from solution PL. These data indicate that Ca2+ uptake by the SR in situ depends on a local ATP:ADP ratio that is controlled by both CK and glycolytic enzymes. In CK-deficient mice, Ca2+ loading was impaired in solution PL due to the absence of CK. In solution GL, loading was significantly increased, such that calculated Ca2+ release parameters were normalized to those in control fibres in solution PL. In CK-deficient mice, fibre kinetic parameters of tension recovery were impaired after quick stretch in solution PL and were not improved in solution GL. These results show that in CK-deficient mice, at least under basal conditions, glycolysis can replace the CK system in fueling the SR Ca2+ ATPase, but not the myosin ATPase, and may in part explain the limited phenotypic alterations seen in the hearts of these mice.
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PMID:Glycolysis supports calcium uptake by the sarcoplasmic reticulum in skinned ventricular fibres of mice deficient in mitochondrial and cytosolic creatine kinase. 1088 44

We investigated the effects of two purported calcium sensitizing agents, MCI-154 and DPI 201-106, and a known calcium sensitizer caffeine on Mg-ATPase (myofibrillar ATPase) and myosin ATPase activity of left ventricular myofibrils isolated from non-failing, idiopathic (IDCM) and ischemic cardiomyopathic (ISCM) human hearts (i.e. failing hearts). The myofibrillar ATPase activity of non-failing myofibrils was higher than that of diseased myofibrils. MCI-154 increased myofibrillar ATPase Ca2+ sensitivity in myofibrils from non-failing and failing human hearts. Effects of caffeine similarly increased Ca2+ sensitivity. Effects of DPI 201-106 were, however, different. Only at the 10(-6) M concentration was a significant increase in myofibrillar ATPase calcium sensitivity seen in myofibrils from non-failing human hearts. In contrast, in myofibrils from failing hearts, DPI 201-106 caused a concentration-dependent increase in myofibrillar ATPase Ca2+ sensitivity. Myosin ATPase activity in failing myocardium was also decreased. In the presence of MCI-154, myosin ATPase activity increased by 11, 19, and 24% for non-failing, IDCM, and ISCM hearts, respectively. DPI 201-106 caused an increase in the enzymatic activity of less than 5% for all preparations, and caffeine induced an increase of 4, 11, and 10% in non-failing, IDCM and ISCM hearts, respectively. The mechanism of restoring the myofibrillar Ca2+ sensitivity and myosin enzymatic activity in diseased human hearts is most likely due to enhancement of the Ca2+ activation of the contractile apparatus induced by these agents. We propose that myosin light chain-related regulation may play a complementary role to the troponin-related regulation of myocardial contractility.
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PMID:Mg-ATPase and Ca+ activated myosin AtPase activity in ventricular myofibrils from non-failing and diseased human hearts--effects of calcium sensitizing agents MCI-154, DPI 201-106, and caffeine. 1270 47

Lead (Pb2+) poisoning causes hypertension, but little is known regarding its acute effects on cardiac contractility. To evaluate these effects, force was measured in right ventricular strips that were contracting isometrically in 45 male Wistar rats (250-300 g) before and after the addition of increasing concentrations of lead acetate (3, 7, 10, 30, 70, 100, and 300 microM) to the bath. Changes in rate of stimulation (0.1-1.5 Hz), relative potentiation after pauses of 15, 30, and 60 s, effect of Ca2+ concentration (0.62, 1.25, and 2.5 mM), and the effect of isoproterenol (20 ng/mL) were determined before and after the addition of 100 microM Pb2+. Effects on contractile proteins were evaluated after caffeine treatment using tetanic stimulation (10 Hz) and measuring the activity of the myosin ATPase. Pb2+ produced concentration-dependent force reduction, significant at concentrations greater than 30 microM. The force developed in response to increasing rates of stimulation became smaller at 0.5 and 0.8 Hz. Relative potentiation increased after 100 microM Pb2+ treatment. Extracellular Ca2+ increment and isoproterenol administration increased force development but after 100 microM Pb2+ treatment the force was significantly reduced suggesting an effect of the metal on the sarcolemmal Ca2+ influx. Concentration of 100 microM Pb2+ also reduced the peak and plateau force of tetanic contractions and reduced the activity of the myosin ATPase. Results showed that acute Pb2+ administration, although not affecting the sarcoplasmic reticulum activity, produces a concentration-dependent negative inotropic effect and reduces myosin ATPase activity. Results suggest that acute lead administration reduced myocardial contractility by reducing sarcolemmal calcium influx and the myosin ATPase activity. These results also suggest that lead exposure is hazardous and has toxicological consequences affecting cardiac muscle.
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PMID:Lead reduces tension development and the myosin ATPase activity of the rat right ventricular myocardium. 1882 Jul 69

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