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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe the effects of various cardioactive compounds on the Ca++ activation of force production and ATPase activity in isolated contractile structures from mammalian heart and, in some cases, skeletal muscle. We show that: 1) the Ca++ sensitizing activity of APP 201-533 does not discriminate between cardiac and skeletal muscle and is, therefore, not based on interaction with cardiac troponin I phosphorylation at serine 20. 2) compounds like trifluoperazine or bepridil, both known to interact with calmodulin, increase the Ca++ sensitivity of the contractile structures of the heart, in high concentrations, as expected from the high natural abundance of troponin C. 3) DPI 201-106 interacts with calmodulin (and presumably with the structurally closely related troponin C) in the microM concentration range. Its high Ca(++)-sensitizing potency in skinned cardiac muscle and a certain sensitivity of this effect to the detergent Triton X-100 suggest accumulation of the hydrophobic compound in the myofibrillar protein lattice.
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PMID:On the role of Ca++ binding proteins as possible targets for Ca++ sensitizing agents. 129 Mar 6

The inotropic actions of various drugs known to increase force of contraction in isolated mammalian cardiac muscle were investigated in electrically driven (1 Hz) guinea-pig left atria under both normal [K+]o (4.7 mM) and high [K+]o (22 mM). Under normal [K+]o a concentration-dependent increase in force of contraction could be confirmed with the beta-adrenoceptor agonist, isoprenaline, the cyclase activator, forskolin, the inhibitors of the cyclic AMP-phosphodiesterase (PDE), amrinone, IBMX, and OPC 8212, the Na+ channel activators, DPI 201-106, SDZ 210-921, veratridine, and ATX II, the Na(+)-ionophore monensin, the inhibitor of Na+/K(+)-ATPase, ouabain, and the Ca2+ channel activators, Bay K 8644, CGP 28 H 392, and SDZ 202-791. Partial depolarization of the muscle preparations by increasing [K+]o in the organ bath to 22 mM completely abolished the positive inotropic action of the Na+ channel-activating drugs. In contrast, the effects of the other compounds were still present, although changes in the maximal force development were observed. The efficacy of the PDE inhibitors amrinone and IBMX were slightly increased; the maximal effects of isoprenaline, monensin, forskolin, and OPC 8212 were unchanged; the effect of ouabain decreased to about half maximal values; while the efficacy of the Ca2+ channel activators were either unchanged (CGP 28 392) or decreased (Bay K 8644 and SDZ 202-791). The results suggest that inactivation of cardiac fast Na+ channels by partially depolarizing isolated, electrically driven atria is a suitable model to distinguish between cardiotonic agents acting through activation of Na+ channels and those with other mechanisms of action.
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PMID:Identification of cardiotonic sodium channel activators by potassium depolarization in isolated guinea-pig atria. 170 Feb 27

This review deals with the principal mechanisms which are known to play a role in positive inotropism: 1) The myoplasmic Ca2+ concentration may be increased by increases in cyclic AMP. Beside receptor-mediated stimulation (isoprenaline) or direct stimulation (forskolin) of the adenylate cyclase, the cyclic AMP may be increased by phosphodiesterase inhibition; 2) Cyclic AMP-independent activation of Ca2+ channels can be brought about by alpha-adrenergic agents (phenylephrine) or so-called calcium agonists; 3) Only a small increase in myoplasmic Na+ concentration can greatly enhance the force of contraction by an increase in the intracellular Ca2+ concentration. This is possible by inhibition of the Na+/K+-ATPase (glycosides) or by prolongation of the open state of Na+ channels (DPI 201-106); 4) A direct inhibition of the Na+/Ca2+ exchange has been discussed for amiloride; 5) A prolongation of the action potential induced by K+ channel-inhibiting agents such as 4-amino-pyridine may increase the myoplasmic Ca2+ concentration by a prolongation of the slow Ca2+ inward current; 6) An increased Ca2+ sensitivity of the contractile proteins has been demonstrated for a number of compounds in vitro; the contribution of such an effect to the overall positive inotropism is unknown because a calcium sensitizer without any effects on calcium or sodium movements is not yet available.
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PMID:Mechanisms of positive inotropic effects. 255 73

The effects of DPI 201-106 were examined on contractions of papillary muscles from the right ventricle of feline heart, on [3H]-ouabain binding and Na+, K+-ATPase activity in feline ventricular membrane particles and on ouabain-sensitive 86Rb uptake in human erythrocytes. DPI 201-106 partially inhibited the Na+ pump at concentrations that caused pronounced positive inotropic effects.
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PMID:Inhibition of the sodium pump by cardioactive DPI 201-106. 295 4

Positive inotropic substances which enhance the myocardial cAMP level or inhibit the Na+/K(+)-ATPase are known for their proarrhythmic side-effects. This study was performed to investigate the inotropic and arrhythmogenic action of the Na(+)-channel activator BDF 9148 (racemate) in comparison to its S-enantiomer BDF 9196, its congener DPI 201-106 (racemate), to norepinephrine, and to ouabain. In 30 open-chest dogs, the effects of these substances on the first derivative of left ventricular pressure (dP/dt, Millar-tip catheter) and anterior systolic wall thickening (AWT, sonomicrometry) were studied. Concomitantly, myocardial excitability, conduction times, and refractory period were assessed with a transmural, three-dimensional, 16-electrode array in the anterior wall. For the study of the Na(+)-channel activators, alpha- and beta-adrenergic and muscarinic receptors were blocked. A first set of measurements was performed during normoperfusion with administration of BDF 9148 (1 mg/kg, n = 8), BDF 9196 (0.5 mg/kg, n = 8), and DPI 201-106 (1 mg/kg, n = 8), respectively. A second set of measurements was performed with administration of the threefold dosage of either substance. With a severe stenosis on the left anterior descending coronary artery, a final set of measurements was performed, again using the higher dosage of either substance. For the study of norepinephrine (0.5 micrograms/kg/min i.v., n = 6) and ouabain (40 micrograms/kg i.v., n = 4), measurements were performed during normoperfusion in additional animals. Under normal conditions, either Na(+)-channel activator induced increases in dP/dtmax (lower dosage: 45-84%, higher dosage: by 93-117%) and AWT (lower dosage: by 24-37%, higher dosage: by 19-56%). Under ischemic conditions, either drug increased dP/dtmax by 60-98% and AWT by 45-102%. Excitability, conduction times, and refractory period did not change significantly in response to the Na(+)-channel activators, neither under normal nor under ischemic conditions. There was no significant difference in the incidence of spontaneous ventricular extrasystoles before and after administration of either Na(+)-channel activator. In contrast, an equi-inotropic dosage of norepinephrine (increases in dP/dtmax by 148% and AWT by 42%) increased excitability, decreased conduction times and refractory period, and increased the incidence of spontaneous ventricular extrasystoles. Ouabain induced only a moderate increase in dP/dtmax by 56% and AWT by 24%, but elicited sustained and complex ventricular arrhythmias. Excitability was markedly increased, whereas conduction times and refractory period changed only little.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Characterization of the inotropic and arrhythmogenic action of the sodium channel activator BDF 9148: a comparison to its S-enantiomer BDF 9196, to its congener DPI 201-106, to norepinephrine, and to ouabain. 801 Sep 37

Four renal cell lines were derived from glomeruli, proximal, distal, and cortical collecting tubules microdissected from the kidneys of transgenic mice carrying the temperature-sensitive mutant of the simian virus 40 large T antigen under the control of the vimentin promoter. All four cell lines contained large T antigen in their nuclei, grew rapidly, and contained vimentin filaments when grown in serum-enriched medium at the permissive temperature of 33 degrees C. The glomerular cell line formed multiple layers of cells and contained smooth muscle actin and desmin filaments, features of mesangial cells. The three tubule cell lines formed monolayers of polarized cuboid cells separated by tight junctions and having a patchy distribution of cytokeratins K8-K18. A shift from 33 degrees C to the restrictive temperature (39.5 degrees C) stopped cell growth in all cell lines and caused profound changes in the content of intermediate filaments. Vimentin was still present in mesangial-like cells, but the proximal, distal, and collecting tubule cells contained uniform networks of cytokeratins K8-K18 and desmoplakin I and II around the cell peripheries. Potassium transport, mediated by Na+-K+ ATPase pumps and specific cAMP hormonal sensitivities, significantly increased in proximal, distal, and collecting tubule cells when shifted from 33 degrees C to 39.5 degrees C. Thus, the temperature-dependent inactivation of large T antigen, responsible for the arrest of cell growth, did not affect the phenotype of mesangial-like glomerular cells but induced some changes in the expression of intermediate filaments and restored, at least partially, the main parental cell-specific functions in proximal, distal, and collecting tubule cultured cells.
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PMID:Relationships between intermediate filaments and cell-specific functions in renal cell lines derived from transgenic mice harboring the temperature-sensitive T antigen. 869 37

Cardiac intracellular Na+and Ca2+homeostasis is regulated by the concerted action of ion channels, pumps and exchangers. The Na+, K+-ATPase produces the electrochemical concentration gradient for Na+, which is the driving force for Ca2+removal from the cytosol via the Na+/Ca2+exchange. Reduction of this gradient by increased intracellular Na+concentration leads to cellular Ca2+overload resulting in arrhythmias and contractile dysfunction. Na+and Ca2+overload-associated arrhythmias can be produced experimentally by inhibition of Na+efflux (digitalis-induced intoxication) and by abnormal Na+influx via modulated Na+channels (veratridine, DPI 201-106; hypoxia) or via the Na+, H+exchanger. Theoretically, blockers of Na+and Ca2+channels, inhibitors of abnormal oscillatory release of Ca2+from internal stores or modulators of the Na+, Ca2+and Na+, H+exchanger activities could protect against cellular Na+and Ca2+overload. Three exemplary drugs that prevent Na+and Ca2+overload, i.e. the benzothiazolamine R56865, the methylenephenoxydioxy-derivative CP-060S, and the benzoyl-guanidine Hoe 642, a Na+, H+exchange blocker, are briefly reviewed with respect to their efficacy on digitalis-, veratridine- and ischaemia/reperfusion-induced arrhythmias.
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PMID:Drugs preventing Na+ and Ca2+ overload. 1009 40

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

Nuclear factor kappa B (NF-kappaB) is a redox-associated transcription factor that is involved in the activation of survival pathways. We have previously shown that deoxycholate (DOC) activates NF-kappaB in hepatocytes and colon epithelial cells and that persistent exposure of HCT-116 cells to increasing concentrations of DOC results in the constitutive activation of NF-kappaB, which is associated with the development of apoptosis resistance. The mechanisms by which DOC activates NF-kappaB in colon epithelial cells, and whether natural antioxidants can reduce DOC-induced NF-kappaB activation, however, are not known. Also, it is not known if DOC can generate reactive oxygen species within mitochondria as a possible pathway of stress-related NF-kappaB activation. Since we have previously shown that DOC activates the NF-kappaB stress-response pathway in HCT-116 cells, we used this cell line to further explore the mechanisms of NF-kappaB activation. We found that DOC induces mitochondrial oxidative stress and activates NF-kappaB in HCT-116 cells through multiple mechanisms involving NAD(P)H oxidase, Na+/K+-ATPase, cytochrome P450, Ca++ and the terminal mitochondrial respiratory complex IV. DOC-induced NF-kappaB activation was significantly (P < 0.05) inhibited by pre-treatment of cells with CAPE, EGCG, TMS, DPI, NaN3, EGTA, Ouabain and RuR. The NF-kappaB-activating pathways, induced by the dietary-related endogenous detergent DOC, provide mechanisms for promotion of colon cancer and identify possible new targets for chemoprevention.
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PMID:Deoxycholate induces mitochondrial oxidative stress and activates NF-kappaB through multiple mechanisms in HCT-116 colon epithelial cells. 1688 64

Serotonin (5-HT) stimulates smooth muscle cell growth through 5-HT receptors and the 5-HT transporter (5-HTT), and has been associated with pulmonary hypertension (PH). Platelet-derived growth factor receptors (PDGFR) have also been associated with PH. We present evidence for the first time that 5-HT transactivates PDGFRbeta through the 5-HTT in pulmonary artery (PA) SMCs. Inhibition of PDGFR kinase with imatinib or AG1296 blocks 5-HT-stimulated PDGFRbeta phosphorylation. 5-HTT inhibitors and the Na+/K+-ATPase inhibitor ouabain, but not 5-HT2 and 5-HT1B/1D receptor inhibitors, block PDGFRbeta activation by 5-HT. Notably, 5-HTT binds the PDGFRbeta upon 5-HT stimulation and the 5-HTT inhibitor fluoxetine blocks both the binding and PDGDRbeta activation. Activation of PDGFRbeta may occur through oxidation of a catalytic cysteine of tyrosine phosphatase. 5-HT-activated PDGFRbeta phosphorylation is blocked by the antioxidant N-acetyl-L-cysteine and the NADPH oxidase inhibitor, DPI. Inhibition of PDGFR kinase with imatinib or AG1296 significantly inhibits SMC proliferation and migration induced by 5-HT in vitro. Infusion of 5-HT by miniosmotic pumps enhances PDGFRbeta activation in mouse lung in vivo. In summary, these results demonstrate that 5-HT transactivates PDGFRbeta in PASMCs leading to SMC proliferation and migration, and may be an important signaling pathway in the production of PH in vivo.
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PMID:The 5-HT transporter transactivates the PDGFbeta receptor in pulmonary artery smooth muscle cells. 1750 74


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