Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to determine whether phosphoinositide metabolism is altered in hypertensive cardiac hypertrophy, phospholipase C (PLC) and protein kinase C activities were measured in hearts from 4- and 20-week-old spontaneously hypertensive rats (SHR) and age-matched, normotensive Wistar-Kyoto rats (WKY). PLC activities were assayed using phosphatidylinositol (PI) and phosphatidylinositol-4,5-bisphosphate (PIP2) as substrates to assess the substrate specificity. PI-hydrolyzing PLC activity (PI-PLC) was predominantly located in the cytosol, and its activity was similar in both strains. Membrane-bound PIP2-hydrolyzing PLC activity (PIP2-PLC) was significantly lower in 20-week-old SHR than in WKY, but there was no significant difference in soluble PIP2-PLC. Protein kinase C activity was significantly elevated in 20-week-old SHR and Ca2(+)-phospholipid-dependent phosphorylation was observed in the proteins of molecular weight 26, 32, 43, and 95 KDa. In 4-week-old prehypertensive SHR, there were no significant differences in PI-PLC, PIP2-PLC, or protein kinase C activities as compared with age-matched WKY. These data demonstrated that protein kinase C and membrane-bound PIP2-PLC are altered during the period of hypertension development. These alterations may have important roles in the development or maintenance of hypertensive cardiac hypertrophy in SHR.
Basic Res Cardiol
PMID:Alterations of phosphoinositide-specific phospholipase C and protein kinase C in the myocardium of spontaneously hypertensive rats. 217 34

The possibility, that a GTP-binding protein is involved in the transducing mechanism leading to the formation of inositol trisphosphate (InsP3) in heart was explored in rat heart ventricles. Accordingly, a crude membrane fraction was isolated from 3[H] inositol prelabelled rat heart ventricles. When incubated with the non-hydrolysable GTP analogues GTP gamma S and GMP-PNP, it produced InsP3 in a time- and concentration-dependent manner. GDP beta S and the aminoglycoside antibiotic neomycin were effective inhibitors of this activation. In the absence of GTP gamma S or GMP-PNP, no such formation occurred with Ca2+ concentration from 10 nM to 1 microM but formation tripled in relation to the control level when Ca2+ concentration was raised from 1 microM to 100 microM. GTP gamma S increased the Ca2+ sensitivity of InsP3 production towards more physiologically relevant concentrations occurring during diastole (100 nM). These findings strongly suggest the presence in heart of a particulate Ca2(+)-dependent phospholipase C, whose activity is regulated by guanine nucleotides. This Ca2(+)-dependent phospholipase C observed in a cell free system was evidenced also in a multicellular system when altering the free Ca2+ concentrations around the physiological range. The results support the possibility that the enzyme might be activated during each cardiac cycle and thus produce two potential activators of cardiac contraction, namely InsP3 and diglycerides.
J Mol Cell Cardiol 1990 Jan
PMID:Mediation by GTP gamma S and Ca2+ of inositol trisphosphate generation in rat heart membranes. 218 85

The effect of global ischemia on myocardial ventricular membrane phospholipids was evaluated using a modified Langendorff preparation. Isolated rat hearts were perfused at 37 degrees C with oxygenated Krebs Ringer solution or rendered ischemic by cessation of perfusion (10 min to 3 h). Longer periods of ischemia were assessed by incubating preperfused (10 min) intact hearts in non-oxygenated Krebs (37 degrees C) for 6 to 18 h. Ischemia-induced alterations in phosphatidylinositol levels and phosphoinositide-specific phospholipase C (PI PLC) activity were assessed in detail, since inositol phospholipids and PI-PLC play putative roles in the regulation of cell function and Ca2+ homeostasis. Decreases in major membrane phospholipids (phosphatidylcholine, phosphatidylserine, cardiolipin and sphingomyelin) were demonstrated after long ischemic periods (6 to 18 h). While periods of ischemia (3 h or less) induced no change in structural phospholipids, an elevation in lysophosphatidylcholine and free fatty acids was found by 1 h. Notably a significant increase in phosphatidylinositol content and an accompanying decrease in cytosolic PI PLC activity was detected by 30 mins of ischemia. Reduced enzymic activity was not due to altered in vitro activation or deactivation of PI-PLC, to a change in the Ca2+ requirement of the enzyme, or to translocation of the enzyme from the cytosol to a membrane fraction. The isolated rat heart made globally ischemic for 30 mins under conditions described for this investigation shows signs of irreversible injury i.e. increased cell Ca2+ content and inability to initiate and maintain rhythmic contraction upon reperfusion. Therefore, it is possible that altered phosphoinositide metabolism may contribute to the evolution of ischemia-elicited irreversible cell injury.
J Mol Cell Cardiol 1987 Jul
PMID:Alterations in phospholipid metabolism in the globally ischemic rat heart: emphasis on phosphoinositide specific phospholipase C activity. 282 96

The release of eicosanoids and endothelium-derived relaxing factor (EDRF) from endothelial cells is thought to involve a calcium-dependent step. Using cultured bovine aortic endothelial cells as a model system, we have examined the relation between agonist-induced changes in inositol polyphosphates and calcium levels within the endothelial cells and extracellular calcium on EDRF release. In a superfusion-cascade system, EDRF was detected by the relaxation of a rabbit aortic ring without endothelium suspended beneath a column of cultured endothelial cells. Endothelial cell stimulation by bradykinin or melittin induced dose-dependent relaxation of the bioassay ring. In addition, bradykinin and melittin stimulated an increase in intracellular calcium concentration in fura-2 loaded endothelial cells and an increase in inositol 1,4,5-trisphosphate (Ins[1,4,5]P3) in cells prelabeled with 3H-myoinositol. Bradykinin stimulation produced transient increases in Ins(1,4,5)P3, fura-2 fluorescence and transient EDRF release. Melittin stimulation induced more prolonged release of EDRF from the endothelial cell column, which was correlated with sustained increases in the fura-2 signal and the level of Ins(1,4,5)P3. Omission of calcium from the cell superfusate attenuated, but did not eliminate, bradykinin-induced EDRF release and the calcium transient, whereas the melittin-induced responses were only slightly attenuated. Endothelial cells clearly demonstrate receptor-activation of phospholipase C and release of sequestered calcium from subcellular sites in response to Ins(1,4,5)P3. These results imply that EDRF release is correlated with increased intracellular calcium levels seen in the absence of extracellular calcium. However, sustained release of EDRF does require influx of extracellular calcium via an undefined mechanism.
Am J Cardiol 1988 Oct 05
PMID:Endothelium-derived relaxing factor release associated with increased endothelial cell inositol trisphosphate and intracellular calcium. 326 34

The myocardium contains diverse cellular components and heterogeneous phospholipid-containing membranes. The major phospholipids are phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositnol, sphingomyelin and cardiolipin. The phospholipases capable of hydrolyzing these membrane lipids include phospholipase A, lysophospholipase, and phosphatidylnositol-specific phospholipase C. Early studies revealed that myocardial phospholipase A with an acid pH is localized to lysosomes; those with more alkaline and neutral activities are present in cytosol, microsomes, mitochondria and sarcolemma. Recently, we have identified phosphatidylinositol-specific phospholipase C activity in bovine myocardium with molecular weights ranging from 40,000 to 271,000. Interestingly, forms I, II and III, had pH optima ranging from 4.5 to 5.5; form III also had significant activity at pH 7.0. All activities were stimulated by calcium, suggesting that they are different from calcium-independent phospholipases C found in liver and brain. The pathophysiological significance of these four cytosolic forms of phospholipase C remains to be determined. Thus, under injury-promoting conditions, phospholipase C appears capable of hydrolyzing membrane-associated phosphatidylinositol and the polyphosphoinositides, whereas phospholipases A and lysophospholiphases appear to prefer non-inositol containing phospholipids. Finally, very recent studies suggest "free radical-triggered lipolysis" by phospholipases as a possible mechanism for production of lysophospholipids in myocardial membranes.
Basic Res Cardiol 1987
PMID:Phospholipases of the myocardium. 331 Sep 98

The effects of various free fatty acids, lysophosphatides and phospholipase treatments on the enzymatic and the non-enzymatic lipid peroxidation capacities in the heart homogenates and subcellular fractions were studied. The results showed a dose related inhibition of both the enzymatic and non-enzymatic lipid peroxidation with free fatty acids. A significant inhibition occurred as early as at the concentration of 25-50 microM of several fatty acids both in homogenates and in organelle fractions. In general, the inhibition was greatest with cis-unsaturated, long-chain fatty acids. The inhibition was also induced by the pretreatment of the homogenates with phospholipase A2 but not with phospholipase C. The lysophosphatidyl cholines (16:0 and 18:1) had a stimulatory effect on the enzymatic lipid peroxidation capacity at the physiological concentrations. The results show that the stimulatory/inhibitory effect of various lipid amphiphiles on lipid peroxidation is strongly structure linked and the mitochondrial fraction is the most susceptible to the injury induced by lipid amphiphiles.
Basic Res Cardiol 1987
PMID:Effects of free fatty acids, lysophosphatides and phospholipase treatment on lipid peroxidation of myocardial homogenates and membrane fractions. 366 7

Colloidal iron staining, calcium binding and enzyme activities were studied in the isolated rat heart sarcolemma. Colloidal iron staining of the sarcolemma revealed a high density of negatively charged sites associated with the cell surface. This membrane fraction was found to have calcium binding activity at both low (0.1 mM) and high (1.25 mM) concentrations of calcium. Pretreatment of the sarcolemma with either trypsin, phospholipase C or neuraminidase, was associated with a reduction in colloidal iron staining as well as decreased calcium-binding activity at high concentrations of calcium. Calcium binding at low concentrations was decreased by both trypsin and neuraminidase. Mg2+ ATPase, Ca2+ ATPase, and Na+-K+ ATPase activities were altered by neuraminidase and trypsin treatments, whereas phospholipase C treatment altered Na+-K+ ATPase only. It is concluded that both surface negative charge and calcium-binding sites associated with the isolated rat heart sarcolemma are contributed by a mosaic of biomolecules including proteins, phospholipids and glycoproteins, and alterations in the surface charge may influence the activities of membrane-bound enzymes.
Basic Res Cardiol
PMID:Negatively charged sites and calcium binding in the isolated rat heart sarcolemma. 616 50

The relationship between creatine phosphokinase (CPK) release and sarcolemmal permeability to divalent cations (Ca2+ and Ba2+) during hypoxia and reoxygenation was studied in the isolated arterially perfused septal preparation of the newborn and adult rabbit. Tissue 47Ca2+ or 133Ba2+ uptake was measured by a juxtaposed gamma-probe. Since Ba2+ is not taken up by the sarcoplasmic reticulum and mitochondria, 133Ba2+ was used to determine sarcolemmal permeability to divalent cations (Ca2+ and Ba2+). In the two age groups, tissue Ca2+ uptake was unchanged during hypoxia and increased significantly during reoxygenation. Ba2+ uptake remained unchanged during hypoxia and reoxygenation. CPK release was small during hypoxia and increased significantly during reoxygenation. The increases in tissue Ca2+ uptake and CPK release in the newborn were significantly less than in the adult. Perfusion with low Ca2+ solutions (0.3 mM, 0.5 mM and 'zero') decreased tissue Ca2+ gain but did not prevent CPK release during reoxygenation. In the muscle perfused with an oxygenated solution containing phospholipase C (0.1 U/ml), the rate of CPK release increased significantly, but tissue Ca2+ uptake and Ba2+ uptake remained unchanged. These data suggest that: (1) sarcolemmal damage (evidenced by enzyme release) during hypoxia and reoxygenation in the newborn is less than in the adult. (2) enzyme release and tissue Ca2+ gain can occur during reoxygenation without significant changes in sarcolemmal permeability to divalent cations (Ca2+ and Ba2+) that can be detected by the present techniques, and (3) enzyme release during reoxygenation is associated with but may not be caused by the increased tissue Ca2+.
J Mol Cell Cardiol 1984 Jun
PMID:The relationship between myocardial enzyme release and Ca2+ uptake during hypoxia and reoxygenation in the newborn and adult heart. 674 87

Cultured neonatal rat cardiac myocytes have been utilized as a model for the study of the effect of variations in cytoplasmic free Ca2+ on the activity of phospholipase C, a key enzyme in agonist-stimulated signal transduction through the phosphoinositide pathway. Cells prelabelled with [3H]inositol were exposed to various agents in an attempt to modulate the cytoplasmic free Ca2+ concentration and the formation of [3H]inositolphosphates (15-30 min) in the presence of Li+ was taken as a measure of phospholipase C activity. Not the basal but the endothelin-1 (10(-8) M) induced [3H]inositolphosphate production (15 min) was stimulated 1.54- and 1.43-fold by A23187 (10 microM external Ca2+) and 50 mM K+ (1.3 mM external Ca2+) treatment of cells, respectively. The phenylephrine (10(-4) M) induced response was also stimulated (1.35-fold) by A23187, however it was 43% inhibited by high K+. Ouabain (10 microM) treatment of cells did not affect either basal or agonist stimulated phosphoinositide turnover. On the other hand, total removal of external free Ca2+ by addition of 50 microM ethylene glycol bis(beta-aminoethyl ether) (N,N,N',N'-tetraacetic acid strongly inhibited (75%) the endothelin-1 induced but not the basal phospholipase C activity. Endothelin-1 binding to its receptor was shown not to be inhibited by the absence of external Ca2+ while resynthesis of [3H]phosphatidylinositol 4,5-bisphosphate was not rate-limiting under this condition. The lack of external Ca2+ eventually resulted in total standstill of the ET-1 induced PtdIns turnover after 30 min. Although not always as predicted, effects on basal and agonist-activated phospholipase C were observed too when cells were treated with low Ca2+ medium, Ca2+ entry blocker nifedipine (1 microM) or Ca(2+)-channel agonist Bay K8644 (1 microM) but most of these effects were only seen after 90 min incubation. Fluorometric (fura-2) measurements showed that total removal of external free Ca2+ for a short period decreased, while short exposure to high K+ increased cytoplasmic free Ca2+ but neither Ca2+ free buffer or nifedipine nor Bay K8644 had any effect. Furthermore, in saponin-permeabilized cardiomyocytes we could demonstrate that basal as well as GTP gamma S (30 microM) stimulated phospholipase C activity was strongly activated by free Ca2+ in the concentration range of 0.1-10 microM. We conclude that in the intact cardiomyocyte the signalling pathway through phospholipase C/phosphatidylinositol 4,5-bisphosphate, stimulated by agonist-receptor interaction that activates GTP-binding proteins as does GTP gamma S, is likely be a Ca2+ dependent process.
J Mol Cell Cardiol 1994 Aug
PMID:Calcium and the endothelin-1 and alpha 1-adrenergic stimulated phosphatidylinositol cycle in cultured rat cardiomyocytes. 752 83

In the present study, we investigated possible mechanisms behind exogenous phospholipase C-induced glycerol production in irreversibly damaged myocytes. Rat ventricular myocytes were preincubated for 60 min in substrate-free Krebs-Henseleit bicarbonate buffer equilibrated with 95% N2-5% CO2 (37 degrees C, pH = 7.4), resulting in exhaustion of cellular high energy phosphates and loss of rod-shaped morphology. At the end of the preincubation period, the incubation vials were divided into two groups; one receiving 10 mU/ml phospholipase C (PC-PLC), whereas the other received an equivalent volume of buffer (control incubations). Incubation was then continued for another 60 min under 95% air-5% CO2 atmosphere. Samples for measurement of metabolite levels were taken immediately after cell isolation, at the end of the preincubation period and at the end of the normoxic incubation period. During the 60 min incubation period following reoxygenation, glycerol output was markedly higher from PC-PLC treated than from control myocytes. However, the elevated glycerol output from these cells was not accompanied by a simultaneous rise in glycerol-3-phosphate, nor was it inhibited by inclusion of pyruvate in the incubation buffer. On the other hand, glycerol output from PC-PLC treated myocytes was effectively inhibited by a diacylglycerol lipase inhibitor (U-57908, The Upjohn Company). Analysis of cellular lipids revealed a 22% reduction of phospholipid in PC-PLC treated myocytes (P < 0.02), while the content of triacylglycerol, diacylglycerol and unesterified fatty acids increased by 76, 261 and 103%, respectively (P < 0.02). No significant changes were observed for these parameters in control myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
J Mol Cell Cardiol 1995 Mar
PMID:Phospholipid degradation in hypoxic/reoxygenated cardiomyocytes in response to phospholipase C from Bacillus cereus. 760 7


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