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

This study explored whether Staphylococcus aureus alpha-toxin can permeabilize the ventricular muscle and whether the treatment can leave cardiac membrane receptors, intracellular Ca2+ stores and the Ca2+ sensitivity of myofilament without damage. After alpha-toxin treatment, the trabeculae from guinea-pig ventricles developed tension at very low Ca2+ concentration ([Ca2+]) (approximately 0.6 microM) in high K+ solution. The trabeculae could contract transiently with 20 mM caffeine after incubating the muscle in a solution containing 0.5 microM [Ca2+]. Phenylephrine (20 microM) with or without GTP gamma S, a non-hydrolyzable analogue of GTP, in the incubating solution did not change the caffeine-induced tension transient. After loading intracellular Ca2+ stores with Ca2+, Ca2+ could be released from the stores by the [Ca2+] of 1.6 microM since the caffeine-induced tension transient was smaller than without Ca2+ releasing protocol. Phenylephrine with or without 100 microM GTP in the releasing solution did not modify the caffeine-induced tension transient. When the muscle was bathed in 1.6 microM Ca2+ solution containing 5 mM EGTA, the developed tension was maintained stably for more than 2 h. Phenylephrine with or without GTP, GTP alone, or 20 microM inositol 1,4,5-trisphosphate (InsP3) did not change the maintained tension. The amplitude and the rate of spontaneous contractions, induced at the free [Ca2+] around 0.5 microM, were not modified by phenylephrine, with or without GTP, and InsP3. These results show that alpha-toxin is useful at least to permeabilize the cardiac muscle to ions and small molecules without damaging the internal membrane and contractile machinery.
 ...
PMID:Contractility of alpha-toxin permeabilized ventricular muscle of guinea pig. 789 6

1. We examined whether or not caffeine caused an endothelium-dependent contraction (EDC) in canine mesenteric artery and whether the endothelium-dependent contracting factors (EDCF) were arachidonic acid metabolites. 2. Caffeine (1, 3 and 10 mM) caused a transient contraction in endothelium-intact arterial strips. Removal of the endothelium significantly attenuated the caffeine (1 and 3 mM)-induced contraction. 3. Caffeine (1 mM)-induced EDC was not affected by quinacrine and manoalide (phospholipase A2 inhibitors), indomethacin and aspirin (cyclo-oxygenase inhibitors), ONO-3078 and S-1452 (thromboxane A2 antagonists) or AA-861 and TMK-777 (lipoxygenase inhibitors). 4. Caffeine (1 mM)-induced EDC was also unaffected by 50-235 (an endothelin A receptor antagonist). In addition, catalase combined treatment with superoxide dismutase, or allopurinol (antioxidant) did not affect the EDC. 5. Gro-PIP and NCDC (phospholipase C inhibitors) did not affect the caffeine-induced EDC. However, wortmannin (a phospholipase D inhibitor) and staurosporine (a protein kinase C inhibitor) attenuated the caffeine-induced EDC. 6. The present experiments demonstrate that caffeine causes an EDC in canine mesenteric artery and suggest that the EDCF mediating this response is probably not arachidonic acid metabolites, endothelin or superoxide. Instead, caffeine-induced EDC may be due to activation of the phospholipase D pathway.
 ...
PMID:An endothelium-dependent contraction in canine mesenteric artery caused by caffeine. 800 88

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.
 ...
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 role of intracellular signal transduction mechanisms in regulating the motility and metabolism of rat spermatozoa in undiluted caudal epididymal fluid (CEF) was examined. Samples of CEF containing immotile spermatozoa were exposed to drugs and other agents that either stimulate signal transduction pathways or mimic the action of their second messengers. Under these conditions, sperm motility in 25-30 nl of CEF was stimulated by calcium ions (Ca2+), N2,2'-O-dibutyrylguanosine 3':5'-cyclic monophosphate (dibutyryl cGMP), cyclic adenosine 3':5'-monophosphate (cAMP), N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dibutyryl cAMP), 8-bromoadenosine 3':5'-cyclic monophosphate (8-bromo cAMP), caffeine, theophylline and bicarbonate ions (HCO3-). Other agents such as magnesium ions (Mg2+), veratridine, phospholipase C (PLC), ionophore A23187, 1,2-dioctenoyl-sn-glycerol (DAG), phorbol 12-myristate 13-acetate, phospholipase A2 (PLA2), arachidonic acid, and melittin did not significantly influence motility. In the presence of radiolabelled energy substrates, untreated (immotile) spermatozoa in samples of CEF utilised D-[U-14C]glucose and [1-14C]acetate as exogenous energy sources for oxidative metabolism. No detectable 14C-lactate was produced, and none of the drugs altered the rate of glycolytic or oxidative metabolism. The findings suggest that the motility of rat caudal epididymal spermatozoa is regulated by Ca2+ and the guanylate cyclase and adenylate cyclase pathways, but not through the PLC and PLA2 pathways. Also, their metabolism of exogenous substrate was uncoupled from the induction of motility, and their oxidative capacity exceeded the rate of flux of glucose-carbon through the glycolytic pathway.
 ...
PMID:Intracellular signal transduction mechanisms of rat epididymal spermatozoa and their relationship to motility and metabolism. 804 68

New bone formation is associated with an increase in blood flow by the invasion of capillaries. Endothelial cells that line the capillaries can produce paracrine factors that affect bone growth and development, and in turn, could be affected by products produced by bone cells, in particular the osteoblasts. Since osteoblasts produce prostaglandins E2 and F2 alpha (PGE2, PGF2 alpha), it was investigated if these PGs were agonists to bone-derived endothelial cells (BBE) by assessing changes in cAMP and free cytosolic calcium concentration ([Ca2+]i) second messenger generation. We found that confluent cultures of BBE cells, a clonal endothelial cell line derived from bovine sternal bone, responded to 1 microM PGE2 by an increase in cAMP. PGF2 alpha at the same concentration was less potent in stimulating an increase in cAMP production in confluent BBE cells. Subconfluent cells with a morphology similar to that of fibroblastic cells were not as sensitive to PGE2-stimulated cAMP generation. PGF2 alpha failed to elicit any cAMP production in subconfluent cultures. PGE2 and PGF2 alpha both stimulated an increase in [Ca2+]i concentration in a dose-dependent manner. The potency of PGE2 was similar to that of PGF2 alpha in stimulating an increase in [Ca2+]i. The Ca2+ response was mostly independent of extracellular Ca+, was unchanged even with prior indomethacin treatment, was unaffected by caffeine pretreatment, but was abolished subsequent to thapsigargin pretreatment. The PG-induced increase in [Ca2+]i was also dependent on the confluency of the cells. In a subconfluent state, the responses to PGE2, or PGF2 alpha were either negligible, or only small increases in [Ca2+]i were noted with high concentrations of these two PGs. Consistent, dose-dependent increases in [Ca2+]i were stimulated by these PGs only when the cells were confluent and had a cobblestoned appearance. Since it was previously demonstrated that BBE cells respond to parathyroid hormone (PTH) by the production of cAMP, we tested if bovine PTH(1-34) amide ]bPTH(1-34) also increased [Ca2+]i in these cells. No change in [Ca2+]i was found in response to bPTH (1-34), although bPTH (1-34) stimulated a nine to tenfold increase in cAMP. We conclude that BBE cells respond to PGE2 and PGF2 alpha but not to bPTH(1-34) by an increase in [Ca2+]i probably secondary to stimulation of phospholipase C and that the cAMP and [Ca2+]i second messenger responses in BBE cells are dependent on the state of confluency of the cells.
 ...
PMID:Prostaglandin-stimulated second messenger signaling in bone-derived endothelial cells is dependent on confluency in culture. 807 96

To understand the contractile response to histamine, drug-induced tension developments were measured in intact and staphylococcal alpha-toxin-treated permeabilized smooth muscle preparations of rabbit lingual artery. Histamine produced an endothelium-independent contraction; the observed effect was antagonized by diphenhydramine and was attenuated by nifedipine. Histamine produced only transient contraction in the Ca(2+)-free bathing media. In permeabilized preparations, histamine-induced contraction was abolished by ryanodine (in the presence of caffeine) or prior repeated application of caffeine; however, contraction produced by IP3 was still observed under the same experimental condition as that of the histamine study. Histamine- or caffeine-induced contraction was abolished in the permeabilized preparations by prior repeated application of IP3; caffeine or IP3 produced contraction after repeated application of histamine. Ryanodine in the presence of histamine was ineffective on caffeine-induced contraction, suggesting that histamine by itself may not have the ability to act on caffeine-sensitive Ca2+ release channels. Neomycin and H-7 completely abolished the histamine-induced contraction. Hence, it is suggested that histamine can contract the lingual artery via H1-receptor-coupled phospholipase C activation, and the contraction consists of a phasic response evoked by Ca2+ release from the IP3- and caffeine-sensitive Ca2+ storage site and the tonic response generated by the voltage-dependent influx of Ca2+. It is also postulated that IP3 produced by histamine may be able to produce Ca2+ release from only a part of the intracellular Ca2+ stores in the smooth muscle of rabbit lingual artery.
 ...
PMID:[A mechanism underlying histamine-induced contraction in isolated rabbit lingual artery]. 817 80

The mechanisms by which the generation and frequency of cytoplasmic Ca2+ oscillations are controlled were investigated in pituitary gonadotrophs. In these cells, two Ca(2+)-mobilizing receptors, the gonadotropin-releasing hormone and endothelin receptors, induce frequency-modulated Ca2+ spiking at the rate of up to 30 min-1. The cytoplasmic oscillator is also activated by discharge of luminal Ca2+ (initiated by ionomycin, thapsigargin, or thimerosal) but not by increased voltage-sensitive Ca2+ influx or treatment with caffeine. The basic difference between these two types of Ca2+ oscillations is related to their requirement for inositol-1,4,5-triphosphate (InsP3). Thapsigargin-, thimerosal-, and ionomycin-induced spiking occurs without the rise in InsP3 production that is essential for the generation of receptor-controlled oscillatory responses. The differential requirement for InsP3 in the two types of Ca2+ spiking is indicated by two lines of evidence. First, agonist-induced Ca2+ spiking of frequency similar to that of non-receptor-mediated oscillations was accompanied by a significant increase in InsP3, whereas none of the non-receptor-mediated oscillations was associated with measurable changes in inositol phosphate production. Second, agonist-induced InsP3 formation and Ca2+ spiking were abolished by treatment with the phospholipase C inhibitors U73122 and neomycin sulfate, whereas non-receptor-mediated Ca2+ spiking was not affected by these agents. When the oscillator was activated by agents that do not increase InsP3 formation, it operated only at the basal rate of approximately 5 min-1 and spiking frequency did not rise with increasing drug concentrations, in contrast to the situation in agonist-stimulated gonadotrophs. However, both types of oscillations were affected by depletion of luminal Ca2+ and by changes in the intracellular Ca2+ concentration ([Ca2+]i) but were not inhibited by ryanodine. These findings are consistent with the operation of a single-pool Ca2+ oscillator that is responsible for generation of both types of Ca2+ oscillations. The oscillator is controlled by the coagonist actions of InsP3 and Ca2+ on the InsP3 receptor channels and by the activation of Ca(2+)-ATPase by rising [Ca2+]i. It can be induced to operate at low frequency without an increase in InsP3 production by agents that reduce intraluminal [Ca2+]i, and it exhibits a dose-dependent increase in spiking frequency during agonist stimulation.
 ...
PMID:Control of calcium spiking frequency in pituitary gonadotrophs by a single-pool cytoplasmic oscillator. 819 91

The kinetics of phosphoinositol 4,5 bisphosphate hydrolysis products in activated Plasmodium falciparum gametocytes suggests a role for inositol trisphosphate [Ins(1,4,5)P3] and diacylglycerol (DAG) in the signal transduction pathway of malaria gametocytes. To investigate further this role, compounds that have an effect on the metabolism and biologic functions of these second messengers were tested in an in vitro system. Gentamycin, 2,3 diphosphoglycerate (2,3 DPG) and magnesium ion (Mg2+), inhibitors of Ins(1,4,5)P3 5' phosphatase, all stimulated gametocytes to exflagellate in suspended animation buffer, pH 7.4, at room temperature. In addition, methylxanthines, caffeine and theobromine, calcium ionophore (A-23187), and external calcium also stimulated exflagellation. In contrast, neomycin, an aminoglycoside that inhibits phospholipase C activity, and heparin, an antagonist of Ins(1,4,5)P3 binding to its receptor, inhibited microgamete formation. Quinine and chloroquine which can inhibit both phospholipase A and C activity also inhibited gametocyte exflagellation. The consistent manner in which these various compounds affect gametocyte activation further implicates phosphoinositol turnover in the signal transduction pathway of falciparum gametocytes.
 ...
PMID:Use of pharmacological agents to implicate a role for phosphoinositide hydrolysis products in malaria gamete formation. 824 Apr 17

Neurotransmitters induce contractions of smooth muscle cells initially by mobilizing Ca2+ from intracellular Ca2+ stores through inositol 1,4,5-trisphosphate (InsP3) receptors. Here we studied roles of the molecules involved in Ca2+ mobilization in single smooth muscle cells. A slow rise in cytoplasmic Ca2+ ([Ca2+]i) in agonist-stimulated smooth muscle cells was followed by a wave of rapid regenerative Ca2+ release as the local [Ca2+]i reached a critical concentration of approximately 160 nM. Neither feedback regulation of phospholipase C nor caffeine-sensitive Ca(2+)-induced Ca2+ release was found to be required in the regenerative Ca2+ release. These results indicate that Ca(2+)-dependent feedback control of InsP3-induced Ca2+ release plays a dominant role in the generation of the regenerative Ca2+ release. The resulting Ca2+ release in a whole cell was an all-or-none event, i.e. constant peak [Ca2+]i was attained with agonist concentrations above the threshold value. This finding suggests a possible digital mode involved in the neural control of smooth muscle contraction.
 ...
PMID:Critical intracellular Ca2+ concentration for all-or-none Ca2+ spiking in single smooth muscle cells. 826 71

The effects of the antimalarial agent mefloquine on directly stimulated rat hemidiaphragm were investigated after nerve transmission had been blocked with alpha-bungarotoxin. Mefloquine (50 and 75 microM) caused contractures and diminished directly stimulated twitch responses. The mefloquine-induced contracture was significantly diminished in low Ca2+ Krebs-Henseleit solution and after pretreatment with phospholipase C. It was potentiated following an initial exposure to ryanodine. Mefloquine, as well as ryanodine, reduced the caffeine contractures obtained in low Ca2+ media. The results suggest that Ca(2+)-induced Ca2+ release, involving the action of mefloquine on some phospholipid component of the sarcolemma, appears to be important in the initiation of the contracture. The loss in caffeine response following pretreatment with mefloquine indicates that mefloquine also causes depletion of Ca2+ from sarcoplasmic reticulum stores.
 ...
PMID:Comparison of the effects of mefloquine and ryanodine on the directly stimulated rat hemidiaphragm preparation. 839 89


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>