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)

1. Small strips from third-order branches of rabbit mesenteric artery (approximately 150-200 microM wide) contracted in response to noradrenaline (10 microM) or 5-hydroxytryptamine (5-HT; 10 microM) in oxygenated Krebs solution containing 2.5 mM Ca2+. In a Ca(2+)-free mock intracellular solution (0 Ca2+ plus 0.2 mM EGTA), noradrenaline (10 microM) and caffeine (10 mM) induced only a single, transient contraction in artery strips, while 5-HT (10 microM) failed to induce any response. 2. In strips of mesenteric artery which had been permeabilized with Staphylococcus alpha-toxin and bathed in Ca(2+)-free mock intracellular solution, noradrenaline (10 microM), caffeine (10 mM) and D-myo-inositol (1,4,5)-trisphosphate (IP3, 100 microM), but not 5-HT (10 or 100 microM) induced a transient contraction. In contrast to the non-permeabilized strips, contractions to noradrenaline, caffeine and IP3 were restored by prior incubation (10 min) in solution containing 0.08 microM Ca2+. The contractions to noradrenaline and IP3 in permeabilized muscle strips required the presence of 100 microM guanosine 5'-triphosphate (GTP), although in the absence of Ca2+. GTP alone did not induce contraction. 3. Exposure of permeabilized mesenteric artery strips to IP3 significantly reduced the subsequent contractile responses to caffeine. Contractile responses to caffeine and IP3 were abolished by the Ca(2+)-ATPase inhibitor, thapsigargin (1 microM). 4. Ca2+ (0.1-10 microM) induced concentration-dependent contraction in permeabilized artery strips. In strips which were submaximally contracted with 0.5 microM Ca2+/100 microM GTP, the subsequent addition of 5-HT (10 microM) stimulated further contraction. The protein kinase C inhibitor, H-7 (1 microM) abolished the 5-HT/GTP-induced contraction, but did not alter the contraction to Ca2+. 5. In non-permeabilized, endothelium-denuded segments of rabbit mesenteric artery bathed in Ca2+-replete Krebs solution, noradrenaline (10 microM) stimulated a rapid, transient accumulation of IP3. 5-HT(100 microM) failed to stimulate IP3 accumulation during exposure periods of up to 5 min. 5-HT (100 microM)did stimulate IP3 accumulation if the external K+ concentration was raised (to around 25 mM). This concentration of K+ alone did not stimulate IP3 production and the 5-HT-stimulated IP3 accumulation in the presence of elevated extracellular [K+] was abolished by the alpha l-adrenoceptor antagonist, prazosin(O.1 microM).6. These results suggest that intracellular Ca2+ release does not play an important role in 5-HT-induced smooth muscle contraction in the rabbit mesenteric artery. This is despite the fact that a significant intracellular Ca2+ pool is present in these cells, which can be discharged by either noradrenaline or IP3.However, 5-HT did stimulate smooth muscle contraction in the presence of raised intracellular calcium,suggesting that a component of the contraction to 5-HT will reflect an increase in myofilament Ca2+sensitivity, possibly due to the activation of protein kinase C.
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PMID:Importance of inositol (1,4,5)-trisphosphate, intracellular Ca2+ release and myofilament Ca2+ sensitization in 5-hydroxytryptamine-evoked contraction of rabbit mesenteric artery. 800 97

The effects of aclarubicin on phosphatidylinositol hydrolysis and contractile responses were investigated in isolated rat aorta. In the aclarubicin-pretreated aorta, the basal level of [3H]inositol monophosphate accumulation was significantly lower whereas [3H]phosphoinositide formation was significantly higher than in the saline-pretreated control aorta. Phenylephrine-, 5-hydroxytryptamine- and sodium fluoride-stimulated increases in [3H]inositol monophosphate accumulation were also significantly reduced in the aclarubicin-treated aorta compared to the control. Contractile forces induced by 5-hydroxytryptamine and sodium fluoride were markedly diminished in the aclarubicin-treated aorta. These results suggest that aclarubicin inhibits phosphatidylinositol hydrolysis at a level of phospholipase C activation, which is involved in the reduction of agonist-induced contraction of rat aorta.
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PMID:Aclarubicin inhibits phosphatidylinositol hydrolysis and contraction of rat aorta. 802 36

1. The aim of the study was to characterize the effects of hypoxia on agonist-stimulated phospholipase D (PLD) and phospholipase C activity of sheep pulmonary artery cultured smooth muscle cells. 2. Endothelin-1 (ET-1), 5-hydroxytryptamine (5-HT) and the protein kinase C (PKC) activator tetradecanoylphorbol acetate (TPA), stimulated a time- and concentration-dependent increase in [3H]-phosphatidylbutanol accumulation. This was abolished by pretreatment of the cells with the PKC inhibitor, Ro-318220, suggesting that agonist-stimulated phospholipase D activity is dependent upon the activation of PKC. 3. Hypoxia (PO2 20 mmHg for 30 min) stimulated basal [3H]-phosphatidylbutanol accumulation by approximately 2 fold and this activity was abolished by preincubation of the cells with 10 microM Ro-318220. 4. In cells preincubated in low O2 containing medium for 30 min, the subsequent agonist-stimulated accumulation of [3H]-phosphatidylbutanol was reduced. However, the decrease in stimulation was greater for ET-1 and 5-HT than for TPA. 5. ET-1 and TPA stimulated a time-dependent increase in protein kinase C- mediated psuedosubstrate phosphorylation. Following preincubation for 30 min in low O2 containing media, basal pseudosubstrate phosphorylation increased whilst the fold stimulation by TPA and ET-1 decreased. 6. In cells preincubated in low O2 containing medium, ET-1-stimulated [3H]-inositol phosphate accumulation was reduced by approximately 30-40%. This reduction was reversed by preincubation of the cells with Ro-318220. 7. These results suggest a role for PKC in the effects of hypoxia on PLD in pulmonary artery smooth muscle cells.
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PMID:Regulation by hypoxia of endothelin-1-stimulated phospholipase D activity in sheep pulmonary artery cultured smooth muscle cells. 803 56

We recently described the cloning of a fifth member of the 5-hydroxytryptamine (5-HT)1 (serotonin1) receptor class that inhibits adenylyl cyclase, namely the human 5-HT1F receptor (Adham et al. 1993a). In the present study we have examined in greater detail the functional coupling of the 5-HT1F receptor in two different cell lines, NIH-3T3 and LM(tk-) fibroblasts (receptor densities of 1.7 and 4.4 pmol/mg protein, respectively). The maximal inhibitory response elicited by 5-HT was significantly greater in NIH-3T3 as compared to LM(tk-) cells, whereas the EC50 values were comparable. To investigate the relationship between receptor occupancy and inhibition of cAMP accumulation mediated by 5-HT1F receptors in NIH-3T3 cells (and hence the degree of receptor reserve), we used the irreversible receptor antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The half-maximal response required only about 10% receptor occupancy, consistent with a receptor reserve of 90% (88 +/- 2.1%, n = 4) for 5-HT-induced inhibition of FSCA. Despite the presence of such a high degree of receptor reserve, a range of intrinsic activities was displayed by structurally diverse classes of compounds. For example, sumatriptan and lysergol were as efficacious as 5-HT itself and thus acted as full agonists, whereas metergoline and 1-NP behaved as partial agonists and as shown previously (Adham et al. 1993a), methiothepin was a silent antagonist (Kb = 438 nM). We have also investigated activation of additional signal transduction pathways by the 5-HT1F receptor and found that the responses differ in the two cell lines with respect to stimulation of phospholipase C. For example, in NIH-3T3 cells no elevation of inositol phosphates (IP) of [Ca2+]i was observed even at very high agonist concentrations (100 microM). In contrast, in LM(tk-) cells concentrations of 5-HT as low as 10 nM induced stimulation of IP and a rapid increase of [Ca2+]i. The 5-HT1F receptor failed to alter arachidonic acid release in either cell line. The maximal increase in IP accumulation in LM(tk-) cells was modest, averaging about 100% above basal. The increases of IP and [Ca2+]i required 5-HT concentrations less than one order of magnitude greater than those inhibiting FSCA (EC50 = 17, 55 and 8 nM, respectively), and both responses were blocked by 100 microM methiothepin. All three responses (cAMP, IP, and [Ca2+]i) were sensitive to pertussis toxin pre-treatment, suggesting the involvement of Gi/Go protein(s) in these signal transduction pathways.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cell-specific coupling of the cloned human 5-HT1F receptor to multiple signal transduction pathways. 813

Contractile responsiveness of the rat mesenteric artery to the ergot alkaloid ergonovine is enhanced in deoxycorticosterone acetate (DOCA) hypertension. This study determines if this abnormality is mediated through serotonergic or alpha adrenergic receptors and investigates the cellular mechanism of the contraction. Mesenteric arteries were dissected from DOCA hypertensive and normotensive rats for use in isolated tissue experiments. Contractions to 5-hydroxytryptamine, phenylephrine, norepinephrine, dopamine and histamine were of a similar maximum in the hypertensive and sham artery with phenylephrine, dopamine and serotonin more potent in hypertension. Ergonovine contracted hypertensive arteries (maximum = 245 +/- 27 mg) but only minimally in sham arteries (maximum = 83 +/- 19 mg). Endothelium removal did not enhance contraction to ergonovine. The alpha-1 antagonist prazosin (10(-6) M) and the serotonergic antagonist 1-naphthylpiperazine (10(-6) M) shifted the ergonovine concentration response of the hypertensive artery rightward. The alpha-2 receptor antagonist idazoxan (10(-6) M) and dopamine antagonist haloperidol did not affect contraction to ergonovine. Contraction to ergonovine was not altered by indomethacin or 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate and was minimally affected by genistein, indicating that ergonovine does not activate pathways which involve cyclooxygenase, phospholipase C or tyrosine kinases, respectively. The protein kinase C inhibitor chelerythrine (10(-5) M), nifedipine (10(-6) M) and calcium-free medium blocked ergonovine-induced contraction.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanism of ergonovine-induced contraction in the mesenteric artery from deoxycorticosterone acetate-salt hypertensive rat. 818 28

An investigation was undertaken of the mechanism by which oxyhemoglobin and its analog methemoglobin might cause cerebrovascular spasm. The effect of these compounds on the levels of intracellular inositol triphosphate and calcium in cultured primate cerebrovascular smooth-muscle cells and the contractile action of oxyhemoglobin on isolated rings of primate cerebral arteries were also examined. Oxyhemoglobin, but not methemoglobin, produces a transient but highly significant increase in the intracellular levels of inositol triphosphate. Intracellular calcium levels in these cells are increased by thrombin, aluminum tetrafluoride, and oxyhemoglobin, and the sustained elevation in intracellular calcium is prevented by ethyleneglycol tetra-acetic acid and the phospholipase C inhibitor neomycin. Removal of the oxyhemoglobin after as long as 48 hours' incubation with this compound allowed cells to rapidly reduce their intracellular calcium levels to near normal. Oxyhemoglobin produced contractions of isolated rings of both normal and spastic cerebral arteries, although the response of spastic vessels was significantly smaller. This effect was inhibited by neomycin. The addition of neomycin relaxed arteries that were contracted with oxyhemoglobin, 5-hydroxytryptamine, or potassium chloride. It is thus likely that activation of phospholipase C is a critical step in the development of vasospasm, but the transient nature of the response to inositol triphosphate suggests that the sustained contraction may arise from other phospholipase C-dependent mechanisms.
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PMID:Intracellular mechanisms involved in the responses of cerebrovascular smooth-muscle cells to hemoglobin. 828 65

Simultaneous addition of 5-hydroxytryptamine (5-HT) and epinephrine synergistically elevated cytosolic free Ca2+ concentration ([Ca2+]cyt) and activated phospholipase C. These phenomena occurred in an agonist concentration-dependent manner and reflected an increase in maximal response rather than a, shift in affinity for either of the stimuli. Ketanserin, a 5HT2 receptor antagonist completely blocked the response of 5-HT plus epinephrine and this in the nanomolar concentration range in which the drug selectively antagonizes 5-HT2 receptor-mediated responses. The synergistic effect was not a consequence of the activation by the platelet-release products ADP and 5-HT nor of influx of extracellular Ca2+. It is concluded that an increased activation of phospholipase C plays a major role in provoking the synergistic effects between 5-HT and epinephrine at the level of signal transduction.
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PMID:The synergistic effect of 5-hydroxytryptamine and epinephrine on the human platelet is related to the activation of phospholipase C. 833 63

The primary phase of ADP-induced aggregation of human platelets does not involve appreciable formation of thromboxane A2 or release of granule contents; lack of formation of inositol trisphosphate has also been noted. Because these responses of platelets to ADP differ so markedly from their responses to other aggregating agents, the roles in ADP-induced aggregation of diacylglycerol, protein kinase C, increases in cytosolic [Ca2+], phosphorylation of pleckstrin (47 kDa) and phosphatases 1 and 2a were investigated. Washed human platelets, prelabelled with [14C]5-hydroxytryptamine and suspended in Tyrode solution (2 mM Ca2+, 1 mM Mg2+), were used for comparisons between the aggregation induced by 2-4 microM ADP, in the presence of fibrinogen, and that induced by 0.05 units/ml thrombin. The diacylglycerol kinase inhibitor 6-(2-[(4-fluorophenyl)phenyl-methylene]-1-piperidinylethyl)-7-meth yl-5H-thiazolo[3,2-a]-pyrimidin-5-one (R59022; 25 microM) had no, or only a slight, enhancing effect on ADP-induced aggregation, but potentiated thrombin-induced responses to a much greater extent. 1,2-Dihexanoyl-sn-glycerol or 1-oleoyl-2-acetyl-sn-glycerol (25 microM) added with or 30-90 s before ADP greatly potentiated aggregation without formation of thromboxane; staurosporine, an inhibitor of protein kinase C, reduced this potentiation. Staurosporine (25 nM) did not inhibit ADP-induced aggregation, although it strongly inhibited thrombin-induced aggregation and release of [14C]5-hydroxytryptamine. All these observations indicate little or no dependence of primary ADP-induced aggregation on the formation of diacylglycerol or on the activation of protein kinase C. At 2-4 microM, ADP did not significantly increase the phosphorylation of pleckstrin (studied with platelets prelabelled with [32P]orthophosphate), but 1,2-dihexanoyl-sn-glycerol- induced phosphorylation of pleckstrin was increased by ADP. Surprisingly, the diacylglycerols strongly inhibited the ADP-induced rise in cytosolic [Ca2+] concurrently with potentiation of ADP-induced aggregation; thus the extent of primary aggregation is independent of the level to which cytosolic [Ca2+] rises. Incubation of platelets with 1,2-dihexanoyl-sn-glycerol or 1-oleoyl-2-acetyl-sn-glycerol for several minutes reversed their potentiating effects on aggregation, and inhibition was observed. Incubation of platelets with okadaic acid, an inhibitor of phosphatases 1 and 2a, inhibited ADP- and thrombin-induced aggregation; although the reason for this effect is unknown, it is unlikely to involve inhibition of phospholipase C, since formation of diacylglycerol appears to have little involvement in the primary phase of ADP-induced aggregation.
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PMID:Activation of phospholipase C and protein kinase C has little involvement in ADP-induced primary aggregation of human platelets: effects of diacylglycerols, the diacylglycerols, the diacylglycerol kinase inhibitor R59022, staurosporine and okadaic acid. 838 48

In this study we have examined the implication of tyrosine kinase activities in aggregation, 5-hydroxytryptamine secretion and mainly phosphoinositide metabolism in response to human platelet stimulation by thrombin. Using the potent tyrosine kinase inhibitor tyrphostin AG-213, we have observed a significant inhibition of aggregation and 5-hydroxytryptamine release; however, this percentage inhibition was lower at high thrombin concentrations. On the other hand, tyrphostin treatment of metabolically 32P-labelled platelets significantly inhibited the thrombin-dependent accumulation of PtdIns(3,4)P2, which involves at least a PtdIns 3-kinase and/or a PtdIns3P 4-kinase, whereas the synthesis of phosphatidic acid (PtdOH), a good reflection of the phospholipase C (PLC) activation in platelets, was partially blocked. Inositol phosphate production was also inhibited by about 40% when tyrphostin-treated platelets were stimulated with thrombin. In addition, we show by Western-blot analysis that PLC gamma 1, as well as the regulatory subunit (p85) of the PtdIns 3-kinase, were present in the anti-phosphotyrosine immunoprecipitate isolated from thrombin-stimulated platelets. Furthermore, tyrphostin treatment clearly decreased the PLC gamma 1 and p85 contents in such an anti-phosphotyrosine immunoprecipitate. Our results provide the first evidence for a direct or indirect regulation of PtdIns(3,4)P2 accumulation and PLC gamma 1 activity by tyrosine phosphorylation during thrombin stimulation of human platelets.
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PMID:Tyrosine kinases and phosphoinositide metabolism in thrombin-stimulated human platelets. 839 Dec 59

We examined the rate and extent of labeling of total cellular phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol (PI) in canine tracheal smooth muscle in response to maximum levels of two different contractile agonists, carbachol (5.5 microM) and serotonin (5-hydroxytryptamine, 5-HT) (47 microM) and when a second agonist was given during a maximal contraction evoked by the first agonist. Unstimulated tracheal smooth muscle strips were incubated with [3H]-myo-inositol (MI) to label tissue MI without much labeling of inositol phospholipids. With carbachol, there was a 20-fold increase in the [3H]-MI incorporation rate into inositol phospholipids, decreases in PI and PIP2 contents, and increases in phosphatidic acid and diacylglycerol contents. PI and PIP2 specific radioactivities reached plateaus, 0.90 +/- 0.03 and 0.80 +/- 0.04, respectively, compared with [3H]-MI specific radioactivity. 5-HT at 47 microM evoked smaller changes including force development, [3H]-MI incorporation rate and lipid mass changes. However, the plateau of PI and PIP2 labeling reached levels similar to that determined during carbachol-evoked force, 0.90 +/- 0.06 and 0.82 +/- 0.04, respectively. Carbachol (55 microM) addition after incubation with 5-HT did not significantly alter the plateau levels of the specific radioactivities of PI or PIP2, although force and lipid mass changes were significantly changed. We conclude that 5-HT and muscarinic receptor coupling mechanisms utilize the same pool of PIP2 as a substrate for phospholipase C activation and the same PI pool for conversion to PIP and PIP2.
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PMID:Common phosphatidylinositol 4,5-bisphosphate pools are involved in carbachol and serotonin activation of tracheal smooth muscle. 839 64


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