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)

Spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were used to investigate the adaptive biochemical changes in the myocardium in response to chronic afterload. Ouabain-inhibited Na+,K+-adenosine triphosphatase (ATPase) activity was decreased by 40% in myocardium of SHR compared with that from WKY, which may lead to increased intracellular Ca2+ through Na+-Ca2+ exchange. Similarly, alpha 1-adrenergic receptor density, estimated by [3H]prazosin binding, was decreased by 42% in myocardial membranes of SHR, while the affinity for the agonist and the antagonist was not altered. In contrast, the number of Ca2+ channels estimated by [3H]nitrendipine binding was increased by 45% in myocardial membranes of SHR, while the affinity was comparable between SHR and WKY. These differences between WKY and SHR in the membrane properties were not due to differential contamination of plasma membranes because the activities of other putative plasma membrane marker enzymes were comparable between WKY and SHR. There were no differences between WKY and SHR in the myosin ATPase activity estimated using myofibrils, actomyosin, and myosin. These results suggest that specific alterations have occurred in the plasma membrane properties of myocardium of SHR that result in altered intracellular Ca2+ metabolism. These alterations may have an important bearing on excitation-contraction coupling in myocardium of SHR.
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PMID:Alterations in the plasma membrane properties of the myocardium of spontaneously hypertensive rats. 242 36

1. The rate of heat production of resting muscle is increased by hypertonic solutions.2. The threshold osmolality required to produce the increased heat rate is less than 2 times normal; at 2.5-3 times normal the heat production rises to 20-50 mcal.g(-1).min(-1), which is 10-20 times the basal rate.3. In anaerobic conditions, the effect of hypertonic solutions on heat rate is only one tenth of that in aerobic conditions.4. A glycerol-treated muscle, with damaged tubular system, still gives a normal response to hypertonic solutions, though it does not respond to raised K(+) concentration.5. The metabolic response to hypertonic solutions is considerably suppressed by procaine.6. Ouabain, 10(-5)-10(-4)M, has no effect.7. The response remains substantial in a muscle which has been depolarized in isotonic K(2)SO(4).8. The membrane potential is slightly reduced by hypertonic solutions, but this cannot account for the increase of the resting metabolism.9. It is suggested that the effect may be due to the release of calcium ions, which produce an increase in myosin ATPase activity.
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PMID:The increase in the rate of heat production of frog's skeletal muscle caused by hypertonic solutions. 425 Aug 26

Chronic ouabain treatment produces hypertension acting on the central nervous system and at vascular levels. However, cardiac effects in this model of hypertension are still poorly understood. Hence, the effects of hypertension induced by chronic ouabain administration ( approximately 8 microg day(-1), s.c.) for 5 weeks on the cardiac function were studied in Wistar rats. Ouabain induces hypertension but not myocardial hypertrophy. Awake ouabain-treated rats present an increment of the left ventricular systolic pressure and of the maximum positive and negative dP/dt. Isolated papillary muscles from ouabain-treated rats present an increment in isometric force, and this effect was present even when inotropic interventions (external Ca(2+) increment and increased heart rate) were performed. However, the sarcoplasmic reticulum activity and the SERCA-2 protein expression did not change. On the other hand, the activity of myosin ATPase increased without changes in myosin heavy chain protein expression. In addition, the expression of alpha(1) and alpha(2) isoforms of Na(+), K(+)-ATPase also increased in the left ventricle from ouabain-hypertensive rats. The present results showed positive inotropic and lusitropic effects in hearts from awake ouabain-treated rats, which are associated with an increment of the isometric force development and of the activity of myosin ATPase and expression of catalytic subunits of the Na(+), K(+)-ATPase.
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PMID:Ouabain-induced hypertension enhances left ventricular contractility in rats. 1671 61