Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Three membrane fractions were studied from canine myocardial left ventricle (LV); crude, light vesicle, and enriched sarcolemma. The percent of the total yield of membrane protein was 99.3 +/- 0.2% for the crude fraction, 0.4 +/- 0.1% for the light vesicle fraction, and 0.3 +/- 0.03% for the purified fraction. Sodium, potassium-ATPase activity in the purified fraction (100 +/- 10.8 mumol Pi/h/mg) was five fold more concentrated than in the light vesicle fraction (18.5 +/- 1.85 mumol Pi/h/mg), and nineteen fold more than in the crude fraction (5.29 +/- 0.57 mumol Pi/h/mg). beta-Adrenergic receptors were 8-fold enriched in the purified fraction (1006 +/- 219 vs 132 +/- 13 fmol/mg in the crude fraction) and 4-fold enriched in the light vesicle fraction (497 +/- 152 fmol/mg). Adenylate cyclase activity was enriched by only 13 to 17-fold in the purified fraction, and only 2 to 4-fold in the light vesicle fraction. The percent of the total beta-adrenergic receptors per gram wet weight was 94 +/- 20% for the crude fraction, 2.1 +/- 0.4% for the light vesicle fraction, and 3.8 +/- 0.7% for the purified fraction. When alamethicin was used to uncover latent enzyme activity, beta-adrenergic receptor density was not affected, but Na+,K(+)-ATPase and adenylate cyclase activity were enhanced in each membrane fraction studied. The surprising finding was that Na+,K(+)-ATPase activity was enriched to the same extent as the beta-adrenergic receptor density in the light vesicle fraction. One potential explanation is that the light vesicle fraction is located in a specialized region of the plasma membrane.
J Mol Cell Cardiol 1990 Dec
PMID:Characterization of subfractions from purified sarcolemma of canine left ventricle. 196 9

Na+,K(+)-ATPase is involved in generating transmembrane ion gradients and the associated potential difference necessary for contraction of cardiac myocytes. It is possible that changes in the activity or membrane content of this enzyme may occur under ischemic conditions. To investigate this question, right ventricular (RV) ischemia was produced in closed chest pigs and the RV ejection fraction was measured using a fast response thermistor in the pulmonary artery. Sections of RV collected at 15, 30, 45, and 60 min of ischemia were assayed for changes in sarcolemmal Na+,K(+)-ATPase activity using an enzyme coupled histochemical reaction as well as a biochemical assay. Similar sections were examined for changes in the distribution and content of Na+,K(+)-ATPase using an immunocytochemical procedure. The RV ejection fraction fell significantly from baseline after 15 min of ischemia (62 +/- 3% vs 39 +/- 3% respectively, P less than 0.05, n = 10). A decrease in sarcolemmal Na+,K(+)-ATPase activity was first detected after 30 min of occlusion and a significant reduction in enzyme activity was present at 45 min of ischemia. In contrast no changes were detected in the distribution or content of immunoreactive Na+,K(+)-ATPase in the sarcolemma at any time point. In addition, the amount of Na+,K(+)-ATPase in tissue homogenates showed no significant changes after 45 min of ischemia. These findings show that acute ischemia results in the disruption of sarcolemmal Na+,K(+)-ATPase activity and suggests that the decrease in enzyme activity is not due to the loss or redistribution of sarcolemmal Na+,K(+)-ATPase.
J Mol Cell Cardiol 1990 Oct
PMID:Immunocytochemical and enzyme histochemical localization of Na+,K(+)-ATPase in normal and ischemic porcine myocardium. 196 61

We now have a biological explanation for most of the physiological characteristics of the hypertrophied chronically overloaded heart: (i) the slowing of the active relaxation is, at least in part, explained by a diminished density in the Ca2+ ATPase of SR, a majority of the modifications in passive myocardial compliance are due to an enhanced collagen density and the diminution of the atrial contribution to ventricular filling is certainly a consequence of an isomyosin change in this particular tissue. (ii) The systolic dysfunction reflects, in fact, one of the most essential parts of the adaptational process, the slowing of Vmax. In human, this diminution is a consequence of a rather complex change in the expression of various genes coding for proteins responsible for myoplasmic calcium transient. (iii) Arrhythmogenecity, a well-known detrimental property of the hypertrophied heart, reflects the fragility of calcium homeostasis in this type of cell, and this fragility is likely to be a direct consequence of the rearrangement of the membrane proteins.
Acta Cardiol 1991
PMID:The biological basis of modified myocardial function in hypertensive cardiopathy. 204 64

Monoclonal and polyclonal antibodies to the major sarcoplasmic reticulum proteins of rabbit skeletal and canine cardiac muscle have been used to identify and characterize the corresponding components of human cardiac sarcoplasmic reticulum. The Ca2(+)-transporting ATPase of human cardiac sarcoplasmic reticulum was identified as a 105,000-Da protein antigenically distinct from its rabbit skeletal muscle counterpart. Human cardiac sarcoplasmic reticulum also contained 53,000- 155,000- and 165,000-Da glycoproteins antigenically related to the low and high molecular weight glycoproteins of canine cardiac and rabbit skeletal muscle sarcoplasmic reticulum. The ryanodine-sensitive Ca2+ channel of human cardiac sarcoplasmic reticulum was identified as a 400,000-Da protein antigenically related to its counterparts in canine cardiac and rabbit skeletal muscle. Human cardiac calsequestrin was identified as a 52,000-Da protein. Human phospholamban was identified as a 29,000-Da substrate for phosphorylation by cAMP-dependent protein kinase. Immunoblots of sarcoplasmic reticulum from the normal left ventricles of four unmatched organ donors and the excised failing left ventricles of nine patients with idiopathic dilated cardiomyopathy were compared in search of qualitative differences in the protein patterns of the failing hearts. No such differences were found with respect to the Ca2+ ATPase, the 53,000-Da glycoprotein, the ryanodine-sensitive Ca2+ channel, calsequestrin or phospholamban. In contrast, the 165,000-Da glycoprotein band, present in all four preparations from nonfailing hearts, was absent from three of nine preparations from failing hearts, and staining of the 155,000-Da glycoprotein in these three preparations appeared to be relatively increased. The absence of the 165,000-Da glycoprotein band may identify or reflect a pathogenetic mechanism in a subset of patients with idiopathic dilated cardiomyopathy.
J Mol Cell Cardiol 1990 Dec
PMID:Identification and characterization of proteins in sarcoplasmic reticulum from normal and failing human left ventricles. 208 60

Several data suggest that in species such as humans, dogs or guinea pigs, sarcomere protein changes do not explain the physiologic modifications that occur in the heart in response to chronic overload. In the guinea pig, e.g., the shortening velocity of an intact papillary muscle negatively correlates with the degree of hypertrophy while the shortening velocity of a skinned hypertrophied fiber does not correlate with heart weight. This review is an attempt to summarize quantitatively data concerning membrane proteins in chronic experimental cardiac overload. With that respect, 2 groups of proteins can be distinguished: (1) the group formed by the calcium-activated adenosine triphosphatase (Ca2(+)-ATPase) of the sarcoplasmic reticulum, the beta 1-adrenergic and muscarinic receptors and the low affinity isoform of the Na+K(+)-ATPase. The synthesis of these proteins is not activated by the process of hypertrophy and consequently their density diminished and their total number per myocyte or per ventricle is unchanged. (2) The second group is formed by the calcium channels and the high affinity isoform of the Na+K(+)-ATPase whose density, in contrast, is unchanged or even increases. Their synthesis is therefore stimulated commensurately with the degree of overload and their total number per myocyte is enhanced. These data suggest that search in the field of inotropes must take into account the fact that the keys that these drugs represent must be modeled as a function of the lock they have to fit into.
Am J Cardiol 1990 Apr 03
PMID:Changes in membrane proteins in chronic mechanical overload of the heart. 213 54

The precise mechanism responsible for the early contractile failure after the onset of myocardial ischemia remains unclear. Physiological studies have reported that intracellular accumulation of inorganic phosphate and intracellular acidosis are the main factors of contractile failure. In contrast, biochemical experiments have shown that the Ca2+ sensitivity of myofibrillar ATPase became less as incubation pH reduces, but the maximal myofibrillar ATPase activity did not change.
J Mol Cell Cardiol 1990 Feb
PMID:Waste of ATP for tension development in myocardial acidosis: chemomechanical uncoupling at myofibrillar level. 213 35

Cardiac ventricular actomyosin was prepared from autopsy samples from humans ranging in age from one to 83 years, and its Ca2(+)-ATPase and K(+)-EDTA-ATPase activities were determined in the presence or absence of a sulfhydryl reagent, N-ethylmaleimide (NEM). The Ca2(+)-ATPase activity increased in the presence of appropriate concentrations of NEM. The extent of the stimulation of Ca2(+)-ATPase activity by NEM decreased significantly with age. The ratio of K(+)-EDTA-ATPase activity to Ca2(+)-ATPase activity also decreased with age. This suggests that there is an age-related modification of sulfhydryl groups in the myosin molecule.
Basic Res Cardiol
PMID:Effect of sulfhydryl group modification on age-associated alteration of actomyosin ATPase activity in human myocardium. 213 23

The cardiac effects of excess growth hormone (GH) were studied in the intact adult rat and in tissues prepared from the rat. Female Wistar-Furth rats were inoculated with a clonal cell line of pituitary cells which secrete GH. Five weeks later, heart weight had increased 37% compared to control (P less than 0.01) due to concomitant increases in left and right ventricular weight. Hemodynamic measurements in the anesthetized rat showed that GH stimulated rats had a decrease in blood pressure and heart rate and a small increase of left ventricular end-diastolic pressure (P less than 0.05). Measurement of left ventricular contractility and relaxation, and response to beta-adrenergic stimulation were decreased in GH compared to control (P less than 0.05). Contractile protein biochemistry showed an 18% reduction in Ca2(+)-myosin ATPase activity of the left ventricle (P less than 0.05) and non-denaturing pyrophosphate gels of purified myosin demonstrated a significant shift of isoforms from the exclusive V1 pattern to both V1 and V3 isomyosins in both ventricles (P less than 0.05). In contrast to the physiological and protein biochemistry adaptations, left ventricular morphology by light microscopy and ultrastructure by electron microscopy were normal in the GH stimulated heart. There were no significant changes in myofibril fraction, in the myofibril to mitochondria ratio or in the capillary numerical density of the hypertrophied left ventricle (P = N.S.). This study demonstrates that under prolonged and extreme stimulation by GH, the heart undergoes considerable growth/hypertrophy. Although cardiac morphology remains normal during this growth, there are alterations of the isomyosins such that ATPase activity is diminished and ventricular function is decreased.
J Mol Cell Cardiol 1990 Apr
PMID:Cardiac physiology, biochemistry and morphology in response to excess growth hormone in the rat. 214 88

An increased venous tone responsible for changes in systemic hemodynamics has been described in borderline hypertensive patients along with the release, in response to intravenous sodium chloride, of an endogenous sodium ion/potassium ion adenosine triphosphatase (Na+/K+ ATPase) inhibitor with vasoconstrictive properties. The hemodynamic and humoral effects of a 2-hour intravenous saline infusion were studied in 25 borderline hypertensives characterized on the basis of their forearm venous distensibility (VV30) in normal (n = 15) and low (n = 10) VV30. VV30 was slightly reduced by saline in the entire hypertensive group (1.47 vs 1.36 ml/100 ml; p less than 0.05), whereas blood pressure and plasma Na+/K+ ATPase inhibitor were unchanged. Normal VV30 showed a sudden increase in plasma Na+/K+ ATPase inhibitor in response to saline associated with an increase in blood pressure, a forearm arterial and venous constriction, and a sluggish suppression in plasma renin activity, whereas low VV30 exhibited a completely opposite pattern. The changes in plasma Na+/K+ ATPase inhibitor inversely correlated to VV30 decreases in borderline hypertensives with normal VV30 (r = -0.49; p less than 0.05), whereas they did not in all hypertensive patients. Atrial natriuretic peptide response to saline infusion was delayed in normal VV30 and inversely related to the changes in Na/K+ ATPase inhibitory activity (r = -42; p less than 0.05) attained after 2 hours of infusion in the entire hypertensive population. Results of this study suggest the ability of acute volume expansion to reduce peripheral venous distensibility in borderline hypertensive patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Cardiol 1990 Sep 01
PMID:Pattern of peripheral venous response to volume expansion in borderline systemic hypertension. 214 96

During hypoxic heart failure, inorganic phosphate (Pi) accumulates. We report the effects of Pi on force development and on myofibrillar ATPase-activity of human skinned atrial fibers, both at normal and at reduced levels of Mg-ATP. Pi (10 mM) depressed force production at maximal calcium activation (pCa 4.3) by about 40%. At higher pCa values (pCa 5.6), force inhibition was even more pronounced, but at low concentrations of Mg-ATP (10 microM), Pi was less effective. In contrast to contractile force, myofibrillar ATPase was only inhibited by about 10% at pCa 4.3, whereas it could be inhibited by 40-50% at submaximal calcium activation (pCa 5.6). As Pi inhibited contractile force more than ATPase activity, the ratio of ATPase-activity to force (tension cost) was increased by inorganic phosphate. ATPase-activity and tension cost were significantly reduced by lowering Mg-ATP concentration to 10 microM, whereas contractile force was less affected. Pi did not affect ATPase under these conditions at 10 mM Mg-ATP. Pi also shifted the calcium-force relationship towards higher Ca++ concentrations, that is, it decreased calcium sensitivity. In contrast, the calcium sensitivity of myofibrillar ATPase was less affected. These findings suggest that inorganic phosphate may affect the myocardium by altering crossbridge kinetics rather than the calcium affinity of troponin-C. Because of its inhibitory effect on myofibrillar ATPase, inorganic phosphate may be partly cardioprotective in the hypoxic myocardium. However, this "energy sparing' effect is probably offset by the greater "tension cost' that decreases the "efficiency' of tension maintenance in the presence of inorganic phosphate.
Basic Res Cardiol
PMID:Inorganic phosphate inhibits contractility and ATPase activity in skinned fibers from human myocardium. 214 47


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