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1.
Micromolar Ca2+ from sparks activates Ca2+-sensitive K+ channels in rat cerebral artery smooth muscle 总被引:3,自引:0,他引:3
Perez Guillermo J.; Bonev Adrian D.; Nelson Mark T. 《American journal of physiology. Cell physiology》2001,281(6):C1769
The goal of the present study was to testthe hypothesis that local Ca2+ release events(Ca2+ sparks) deliver high local Ca2+concentration to activate nearby Ca2+-sensitiveK+ (BK) channels in the cell membrane of arterial smoothmuscle cells. Ca2+ sparks and BK channels were examined inisolated myocytes from rat cerebral arteries with laser scanningconfocal microscopy and patch-clamp techniques. BK channels had anapparent dissociation constant for Ca2+ of 19 µM and aHill coefficient of 2.9 at 40 mV. At near-physiological intracellularCa2+ concentration ([Ca2+]i; 100 nM) and membrane potential (40 mV), the open probability of a singleBK channel was low (1.2 × 106). A Ca2+spark increased BK channel activity to 18. Assuming that 1-100% of the BK channels are activated by a single Ca2+ spark, BKchannel activity increases 6 × 105-fold to 6 × 103-fold, which corresponds to ~30 µM to 4 µM sparkCa2+ concentration.1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acidacetoxymethyl ester caused the disappearance of all Ca2+sparks while leaving the transient BK currents unchanged. Our resultssupport the idea that Ca2+ spark sites are in closeproximity to the BK channels and that local[Ca2+]i reaches micromolar levels to activateBK channels. 相似文献
2.
Intravascular pressure regulates local and global Ca2+ signaling in cerebral artery smooth muscle cells 总被引:1,自引:0,他引:1
The regulationof intracellular Ca2+ signals in smooth muscle cells andarterial diameter by intravascular pressure was investigated in ratcerebral arteries (~150 µm) using a laser scanning confocal microscope and the fluorescent Ca2+ indicator fluo 3. Elevation of pressure from 10 to 60 mmHg increased Ca2+spark frequency 2.6-fold, Ca2+ wave frequency 1.9-fold, andglobal intracellular Ca2+ concentration([Ca2+]i) 1.4-fold in smooth muscle cells,and constricted arteries. Ryanodine (10 µM), an inhibitor ofryanodine-sensitive Ca2+ release channels, or thapsigargin(100 nM), an inhibitor of the sarcoplasmic reticulumCa2+-ATPase, abolished sparks and waves, elevated global[Ca2+]i, and constricted pressurized (60 mmHg) arteries. Diltiazem (25 µM), a voltage-dependentCa2+ channel (VDCC) blocker, significantly reduced sparks,waves, and global [Ca2+]i, and dilatedpressurized (60 mmHg) arteries. Steady membrane depolarization elevatedCa2+ signaling similar to pressure and increased transientCa2+-sensitive K+ channel current frequencye-fold for ~7 mV, and these effects were prevented by VDCCblockers. Data are consistent with the hypothesis that pressure inducesa steady membrane depolarization that activates VDCCs, leading to anelevation of spark frequency, wave frequency, and global[Ca2+]i. In addition, pressure inducescontraction via an elevation of global[Ca2+]i, whereas the net effect of sparks andwaves, which do not significantly contribute to global[Ca2+]i in arteries pressurized to between 10 and 60 mmHg, is to oppose contraction. 相似文献
3.
The hypothesisthat vascular protection in females and its absence in males reflectsgender differences in [Ca2+]i andCa2+ mobilization mechanisms of vascular smooth musclecontraction was tested in fura 2-loaded aortic smooth muscle cellsisolated from intact and gonadectomized male and female Wistar-Kyoto(WKY) and spontaneously hypertensive (SHR) rats. In WKY cells incubated in Hanks' solution (1 mM Ca2+), the resting length and[Ca2+]i were significantlydifferent in intact males (64.5 ± 1.2 µm and 83 ± 3 nM) than inintact females (76.5 ± 1.5 µm and 64 ± 7 nM). In intact male WKY,phenylephrine (Phe, 105 M) caused transient increasein [Ca2+]i to 428 ± 13 nMfollowed by maintained increase to 201 ± 8 nM and 32% cellcontraction. In intact female WKY, the Phe-induced [Ca2+]i transient was notsignificantly different, but the maintained [Ca2+]i (159 ± 7 nM) and cellcontraction (26%) were significantly less than in intact male WKY. InCa2+-free (2 mM EGTA) Hanks', Phe and caffeine (10 mM)caused transient increases in[Ca2+]i and contraction that werenot significantly different between males and females. Membranedepolarization by 51 mM KCl caused 31% cell contraction and increased[Ca2+]i to 259 ± 9 nM in intactmale WKY, which were significantly greater than a 24% contraction and214 ± 8 nM [Ca2+]i in intactfemale WKY. Maintained Phe- and KCl-stimulated cell contraction and[Ca2+]i were significantly greaterin SHR than WKY in all groups of rats. Reduction in cell contractionand [Ca2+]i in intact femalescompared with intact males was significantly greater in SHR (~30%)than WKY (~20%). No significant differences in cell contraction or[Ca2+]i were observed betweencastrated males, ovariectomized (OVX) females, and intact males, orbetween OVX females with 17-estradiol implants and intact females.Exogenous application of 17-estradiol (108 M) tocells from OVX females caused greater reduction in Phe- and KCl-inducedcontraction and [Ca2+]i in SHR thanWKY. Thus the basal, maintained Phe- and depolarization-induced [Ca2+]i and contraction of vascularsmooth muscle triggered by Ca2+ entry from theextracellular space exhibit differences depending on gender and thepresence or absence of female gonads. Cell contraction and[Ca2+]i due to Ca2+release from the intracellular stores are not affected by gender or gonadectomy. Gender-specific reduction in contractility and [Ca2+]i in vascular smoothmuscle of female rats is greater in SHR than WKY rats. 相似文献
4.
Nakao Miki; Ono Kyoichi; Fujisawa Susumu; Iijima Toshihiko 《American journal of physiology. Cell physiology》1999,276(1):C238
A fluid streamthrough a microtube was applied to cultured human aortic endothelialcells to investigate the endothelial responses of both the ioniccurrents and intracellular Ca2+concentration([Ca2+]i)to mechanical stimulation. The fluid stream induced an increase in[Ca2+]ithat was dependent on both the flow rate and the extracellular Ca2+ concentration.Gd3+ and niflumic acid inhibitedthe fluid stream-induced increase in[Ca2+]i,whereas Ba2+ andtetraethylammonium ion exhibited no effect. The fluid stream-induced [Ca2+]iincrease was accompanied by the activation of an inward current at52.8 mV. The reversal potential of the fluid stream-induced current shifted to positive potentials when the externalCl concentration wasreduced but was not affected by variation of the externalNa+ concentration. During theexposure to the fluid stream,[Ca2+]iwas voltage dependent, i.e., depolarization decreased[Ca2+]i.We therefore conclude that the fluid stream-induced current is largelycarried by Cl and that theCl current may thus play arole in modulating the Ca2+ influxby altering the membrane potential of endothelial cells. 相似文献
5.
Morimura K Ohi Y Yamamura H Ohya S Muraki K Imaizumi Y 《American journal of physiology. Cell physiology》2006,290(2):C388-C403
The relative contributions of Ca2+-induced Ca2+ release (CICR) versus Ca2+ influx through voltage-dependent Ca2+ channels (VDCCs) to excitation-contraction coupling has not been defined in most smooth muscle cells (SMCs). The present study was undertaken to address this issue in mouse urinary bladder (UB) smooth muscle cells (UBSMCs). Confocal Ca2+ images were obtained under voltage- or current-clamp conditions. When UBSMCs were activated by a 30-ms depolarization to 0 mV, intracellular Ca2+ concentration ([Ca2+]i) increased in several small, discrete areas just beneath the cell membrane. These Ca2+ "hot spots" then spread slowly through the myoplasm as Ca2+ waves, which continued even after repolarization. Shorter depolarizations (5 ms) elicited only a few Ca2+ sparks, which declined quickly. The number of Ca2+ sparks, or hot spots, was closely related to the depolarization duration in the range of 520 ms. There was an apparent threshold depolarization duration of 10 ms within which to induce enough Ca2+ transients to spread globally and then induce a contraction. Application of 100 µM ryanodine to the pipette solution did not change the resting [Ca2+]i or the VDCC current, but it did abolish Ca2+ hot spots elicited by depolarization. Application of 3 µM xestospongin C reduced ACh-induced Ca2+ release but did not affect depolarization-induced Ca2+ events. The addition of 100 µM ryanodine to tissue segments markedly reduced the amplitude of contractions triggered by direct electrical stimulation. In conclusion, global [Ca2+]i rise triggered by a single action potential is not due mainly to Ca2+ influx through VDCCs but is attributable to the subsequent two-step CICR. Ca2+-induced Ca2+ release; Ca2+-activated K+ current; voltage-dependent Ca2+ channel 相似文献
6.
We determined the effect of aromatic aminoacid stimulation of the human extracellular Ca2+-sensingreceptor (CaR) on intracellular Ca2+ concentration([Ca2+]i) in single HEK-293 cells. Additionof L-phenylalanine or L-tryptophan (at 5 mM)induced [Ca2+]i oscillations from a restingstate that was quiescent at 1.8 mM extracellular Ca2+concentration ([Ca2+]e). Each[Ca2+]i peak returned to baseline values, andthe average oscillation frequency was ~1 min1 at37°C. Oscillations were not induced or sustained if the[Ca2+]e was reduced to 0.5 mM, even in thecontinued presence of amino acid. Average oscillation frequency inresponse to an increase in [Ca2+]e (from 1.8 to 2.5-5 mM) was much higher (~4 min1) than thatinduced by aromatic amino acids. Oscillations in response to[Ca2+]e were sinusoidal whereas those inducedby amino acids were transient. Thus both amino acids andCa2+, acting through the same CaR, produce oscillatoryincreases in [Ca2+]i, but the resultantoscillation pattern and frequency allow the cell to discriminate whichagonist is bound to the receptor. 相似文献
7.
In the presentstudy, we examined the ability of adenosine 3',5'-cyclicmonophosphate (cAMP) to reduce elevated levels of cytosolicCa2+ concentration([Ca2+]i)in pancreatic -cells.[Ca2+]iand reduced pyridine nucleotide, NAD(P)H, were measured in rat single-cells by fura 2 and autofluorescence microfluorometry. Sustained[Ca2+]ielevation, induced by high KCl (25 mM) at a basal glucose concentration (2.8 mM), was substantially reduced by cAMP-increasing agents, dibutyryl cAMP (DBcAMP, 5 mM), an adenylyl cyclase activatorforskolin (10 µM), and an incretin glucagon-likepeptide-1-(7-36) amide (109 M), as well as byglucose (16.7 mM). The[Ca2+]i-reducingeffects of cAMP were greater at elevated glucose (8.3-16.7 mM)than at basal glucose (2.8 mM). An inhibitor of protein kinase A (PKA),H-89, counteracted[Ca2+]i-reducingeffects of cAMP but not those of glucose. Okadaic acid, a phosphataseinhibitor, at 10-100 nM also reduced sustained [Ca2+]ielevation in a concentration-dependent manner. Glucose, but not DBcAMP,increased NAD(P)H in -cells.[Ca2+]i-reducingeffects of cAMP were inhibited by 0.3 µM thapsigargin, an inhibitorof the endoplasmic reticulum (ER)Ca2+ pump. In contrast,[Ca2+]i-reducingeffects of cAMP were not altered by ryanodine, an ERCa2+-release inhibitor,Na+-free conditions, or diazoxide,an ATP-sensitive K+ channelopener. In conclusion, the cAMP-PKA pathway reduces[Ca2+]ielevation by sequestering Ca2+ inthapsigargin-sensitive stores. This process does not involve, but ispotentiated by, activation of -cell metabolism. Together with theknown[Ca2+]i-increasingaction of cAMP, our results reveal dual regulation of -cell[Ca2+]iby the cAMP-signaling pathway and by a physiological incretin. 相似文献
8.
TNF-alpha dilates cerebral arteries via NAD(P)H oxidase-dependent Ca2+ spark activation 总被引:1,自引:0,他引:1
Expression of TNF-, a pleiotropic cytokine, is elevated during stroke and cerebral ischemia. TNF- regulates arterial diameter, although mechanisms mediating this effect are unclear. In the present study, we tested the hypothesis that TNF- regulates the diameter of resistance-sized (150-µm diameter) cerebral arteries by modulating local and global intracellular Ca2+ signals in smooth muscle cells. Laser-scanning confocal imaging revealed that TNF- increased Ca2+ spark and Ca2+ wave frequency but reduced global intracellular Ca2+ concentration ([Ca2+]i) in smooth muscle cells of intact arteries. TNF- elevated reactive oxygen species (ROS) in smooth muscle cells of intact arteries, and this increase was prevented by apocynin or diphenyleneiodonium (DPI), both of which are NAD(P)H oxidase blockers, but was unaffected by inhibitors of other ROS-generating enzymes. In voltage-clamped (40 mV) cells, TNF- increased the frequency and amplitude of Ca2+ spark-induced, large-conductance, Ca2+-activated K+ (KCa) channel transients 1.7- and 1.4-fold, respectively. TNF--induced transient KCa current activation was reversed by apocynin or by Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP), a membrane-permeant antioxidant, and was prevented by intracellular dialysis of catalase. TNF- induced reversible and similar amplitude dilations in either endothelium-intact or endothelium-denuded pressurized (60 mmHg) cerebral arteries. MnTMPyP, thapsigargin, a sarcoplasmic reticulum Ca2+-ATPase blocker that inhibits Ca2+ sparks, and iberiotoxin, a KCa channel blocker, reduced TNF--induced vasodilations to between 15 and 33% of control. In summary, our data indicate that TNF- activates NAD(P)H oxidase, resulting in an increase in intracellular H2O2 that stimulates Ca2+ sparks and transient KCa currents, leading to a reduction in global [Ca2+]i, and vasodilation. cerebrovascular circulation; ryanodine-sensitive Ca2+ release channel; Ca2+-activated K+ channel; reactive oxygen species; vasodilation 相似文献
9.
The lipid bilayertechnique was used to characterize theCa2+ dependence of a fastK+ channel formed by a synthetic17-amino acid segment [OaCNP-39-(1-17)] ofa 39-amino acid C-type natriuretic peptide (OaCNP-39) found in platypus (Ornithorhynchusanatinus) venom (OaV). TheOaCNP-39-(1-17)-formed K+ channel was reversiblydependent on1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-buffered cis (cytoplasmic)Ca2+ concentration([Ca2+]cis).The channel was fully active when[Ca2+]ciswas >104 M andtrans (luminal)Ca2+ concentration was 1.0 mM, butnot at low[Ca2+]cis.The open probability of single channels increased from zero at1 × 106 McisCa2+ to 0.73 ± 0.17 (n = 22) at103 McisCa2+. Channel openings to themaximum conductance of 38 pS were rapidly and reversibly activated when[Ca2+]cis,but not transCa2+ concentration(n = 5), was increased to >5 × 104 M(n = 14). Channel openings to thesubmaximal conductance of 10.5 pS were dominant at5 × 104 MCa2+.K+ channels did not open whencisMg2+ orSr2+ concentrations were increasedfrom zero to 103 M or when[Ca2+]ciswas maintained at 106 M(n = 3 and 2). The Hill coefficientand the inhibition constant were 1 and 0.8 × 104 McisCa2+, respectively. Thisdependence of the channel on high[Ca2+]cissuggests that it may become active under1) physiological conditions whereCa2+ levels are high, e.g., duringcardiac and skeletal muscle contractions, and2) pathological conditions that leadto a Ca2+ overload, e.g., ischemicheart and muscle fatigue. The channel could modify a cascade ofphysiological functions that are dependent on theCa2+-activatedK+ channels, e.g., vasodilationand salt secretion. 相似文献
10.
Regulation of arterial tone by smooth muscle myosin type II 总被引:1,自引:0,他引:1
Löhn M Kämpf D Gui-Xuan C Haller H Luft FC Gollasch M 《American journal of physiology. Cell physiology》2002,283(5):C1383-C1389
Theinitiation of contractile force in arterial smooth muscle (SM) isbelieved to be regulated by the intracellular Ca2+concentration and SM myosin type II phosphorylation. We tested thehypothesis that SM myosin type II operates as a molecular motor proteinin electromechanical, but not in protein kinase C (PKC)-induced,contraction of small resistance-sized cerebral arteries. We utilized aSM type II myosin heavy chain (MHC) knockout mouse model and measuredarterial wall Ca2+ concentration([Ca2+]i) and the diameter of pressurizedcerebral arteries (30-100 µm) by means of digital fluorescencevideo imaging. Intravasal pressure elevation caused a graded[Ca2+]i increase and constricted cerebralarteries of neonatal wild-type mice by 20-30%. In contrast,intravasal pressure elevation caused a graded increase of[Ca2+]i without constriction in (/)MHC-deficient arteries. KCl (60 mM) induced a further[Ca2+]i increase but failed to inducevasoconstriction of (/) MHC-deficient cerebral arteries. Activationof PKC by phorbol ester (phorbol 12-myristate 13-acetate, 100 nM)induced a strong, sustained constriction of (/) MHC-deficientcerebral arteries without changing [Ca2+]i.These results demonstrate a major role for SM type II myosin in thedevelopment of myogenic tone and Ca2+-dependentconstriction of resistance-sized cerebral arteries. In contrast, thesustained contractile response did not depend on myosin andintracellular Ca2+ but instead depended on PKC. We suggestthat SM myosin type II operates as a molecular motor protein in thedevelopment of myogenic tone but not in pharmacomechanical coupling byPKC in cerebral arteries. Thus PKC-dependent phosphorylation ofcytoskeletal proteins may be responsible for sustained contraction invascular SM. 相似文献
11.
Metabolic inhibition with cyanide induces calcium release in pulmonary artery myocytes and Xenopus oocytes 总被引:5,自引:0,他引:5
Wang YX Zheng YM Abdullaev I Kotlikoff MI 《American journal of physiology. Cell physiology》2003,284(2):C378-C388
We examined the effectsof metabolic inhibition on intracellular Ca2+ release insingle pulmonary arterial smooth muscle cells (PASMCs). Severemetabolic inhibition with cyanide (CN, 10 mM) increased intracellularcalcium concentration ([Ca2+]i) and activatedCa2+-activated Cl currents[ICl(Ca)] in PASMCs, responses that were greatlyinhibited by BAPTA-AM or caffeine. Mild metabolic inhibition with CN (1 mM) increased spontaneous transient inward currents andCa2+ sparks in PASMCs. In Xenopus oocytes, CNalso induced Ca2+ release and activatedICl(Ca), and these responses were inhibited by thapsigarginand cyclopiazonic acid to deplete sarcoplasmic reticulum (SR)Ca2+, whereas neither heparin nor anti-inositol1,4,5-trisphosphate receptor (IP3R) antibodies affected CNresponses. In both PASMCs and oocytes, CN-evoked Ca2+release was inhibited by carbonyl cyanidem-chlorophenylhydrazone (CCCP) and oligomycin or CCCP andthapsigargin. Whereas hypoxic stimuli resulted in Ca2+release in pulmonary but not mesenteric artery myocytes, CN induced release in both cell types. We conclude that metabolic inhibition withCN increases [Ca2+]i in both pulmonary andsystemic artery myocytes by stimulating Ca2+ release fromthe SR and mitochondria. 相似文献
12.
The subcellular spatial and temporal organization ofagonist-induced Ca2+ signals wasinvestigated in single cultured vascular endothelial cells.Extracellular application of ATP initiated a rapid increase ofintracellular Ca2+ concentration([Ca2+]i)in peripheral cytoplasmic processes from where activation propagated asa[Ca2+]iwave toward the central regions of the cell. The average propagation velocity of the[Ca2+]iwave in the peripheral processes was 20-60 µm/s, whereas in thecentral region the wave propagated at <10 µm/s. The time course ofthe recovery of[Ca2+]idepended on the cell geometry. In the peripheral processes (i.e.,regions with a high surface-to-volume ratio)[Ca2+]ideclined monotonically, whereas in the central region[Ca2+]idecreased in an oscillatory fashion. Propagating[Ca2+]iwaves were preceded by small, highly localized[Ca2+]itransients originating from 1- to 3-µm-wide regions. The average amplitude of these elementary events ofCa2+ release was 23 nM, and theunderlying flux of Ca2+ amountedto ~1-2 × 1018mol/s or ~0.3 pA, consistent with aCa2+ flux through a single orsmall number of endoplasmic reticulum Ca2+-release channels. 相似文献
13.
Pei Jian-Ming; Yu Xiao-Chun; Bian Jin-Song; Wong Tak-Ming 《American journal of physiology. Cell physiology》1999,277(3):C492
To study the effects of -opioid receptor stimulation onintracellular Ca2+ concentration([Ca2+]i)homeostasis during extracellular acidosis, we determined the effects of-opioid receptor stimulation on[Ca2+]iresponses during extracellular acidosis in isolated single ratventricular myocytes, by a spectrofluorometric method. U-50488H (10-30 µM), a selective -opioid receptor agonist, dosedependently decreased the electrically induced[Ca2+]itransient, which results from the influx ofCa2+ and the subsequentmobilization of Ca2+ from thesarcoplasmic reticulum (SR). U-50488H (30 µM) also increased theresting[Ca2+]iand inhibited the[Ca2+]itransient induced by caffeine, which mobilizesCa2+ from the SR, indicating thatthe effects of the -opioid receptor agonist involved mobilization ofCa2+ from its intracellular poolinto the cytoplasm. The Ca2+responses to 30 µM U-50488H were abolished by 5 µMnor-binaltorphimine, a selective -opioid receptorantagonist, indicating that the event was mediated by the -opioidreceptor. The effects of the agonist on[Ca2+]iand the electrically induced[Ca2+]itransient were significantly attenuated when the extracellular pH(pHe) was loweredto 6.8, which itself reduced intracellular pH(pHi) and increased[Ca2+]i.The inhibitory effects of U-50488H were restored during extracellular acidosis in the presence of 10 µM ethylisopropyl amiloride, a potentNa+/H+exchange blocker, or 0.2 mM Ni2+,a putativeNa+/Ca2+exchange blocker. The observations indicate that acidosismay antagonize the effects of -opioid receptor stimulation viaNa+/H+andNa+/Ca2+exchanges. When glucose at 50 mM, known to activate theNa+/H+exchange, was added, both the resting[Ca2+]iand pHi increased. Interestingly,the effects of U-50488H on [Ca2+]iand the electrically induced[Ca2+]itransient during superfusion with glucose were significantly attenuated; this mimicked the responses during extracellular acidosis. When a high-Ca2+ (3 mM) solutionwas superfused, the resting[Ca2+]iincreased; the increase was abolished by 0.2 mMNi2+, but thepHi remained unchanged. Like theresponses to superfusion with high-concentration glucose andextracellular acidosis, the responses of the[Ca2+]iand electrically induced[Ca2+]itransients to 30 µM U-50488H were also significantly attenuated. Results from the present study demonstrated for the first time thatextracellular acidosis antagonizes the effects of -opioid receptorstimulation on the mobilization ofCa2+ from SR. Activation of bothNa+/H+andNa+/Ca2+exchanges, leading to an elevation of[Ca2+]i,may be responsible for the antagonistic action of extracellular acidosis against -opioid receptor stimulation. 相似文献
14.
Differences in Ca(2+) signaling underlie age-specific effects of secretagogues on colonic Cl(-) transport 总被引:1,自引:0,他引:1
Venkatasubramanian J Selvaraj N Carlos M Skaluba S Rasenick MM Rao MC 《American journal of physiology. Cell physiology》2001,280(3):C646-C658
Taurodeoxycholic acid (TDC) stimulates Cl transport inadult (AD), but not weanling (WN) and newborn (NB), rabbit colonic epithelial cells (colonocytes). The present study demonstrates thatstimuli like neurotensin (NT) are also age specific and identifies theage-dependent signaling step. Bile acid actions are segment and bileacid specific. Thus although TDC and taurochenodeoxycholate stimulateCl transport in AD distal but not proximal colon,taurocholate has no effect in either segment. TDC increasesintracellular Ca2+ concentration([Ca2+]i) in AD, but not in WN and NB,colonocytes. In AD cells, TDC (5 min) action on Cltransport needs intra- but not extracellular Ca2+. NT,histamine, and bethanechol increase Cl transport and[Ca2+]i in AD, but not WN, distalcolonocytes. However, A-23187 increased [Ca2+]i and Cl transport in allage groups, suggesting that Ca2+-sensitive Cltransport is present from birth. Study of the proximal steps inCa2+ signaling revealed that NT, but not TDC, activates aGTP-binding protein, Gq, in AD and WN cells. Inaddition, although WN and AD colonocytes had similar levels ofphosphatidylinositol 4,5-bisphosphate, NT and TDC increased1,4,5-inositol trisphosphate content only in AD cells.Nonresponsiveness of WN cells to Ca2+-dependent stimuli,therefore, is due to the absence of measurable phospholipase Cactivity. Thus delays in Ca2+ signaling afford a crucialprotective mechanism to meet the changing demands of the developing colon. 相似文献
15.
Role of cyclic ADP-ribose in the regulation of [Ca2+]i in porcine tracheal smooth muscle 总被引:1,自引:0,他引:1
Prakash Y. S.; Kannan Mathur S.; Walseth Timothy F.; Sieck Gary C. 《American journal of physiology. Cell physiology》1998,274(6):C1653
The purpose ofthe present study was to determine whether cyclic ADP-ribose (cADPR)acts as a second messenger forCa2+ release through ryanodinereceptor (RyR) channels in tracheal smooth muscle (TSM). Freshlydissociated porcine TSM cells were permeabilized with -escin, andreal-time confocal microscopy was used to examine changes inintracellular Ca2+ concentration([Ca2+]i).cADPR (10 nM-10 µM) induced a dose-dependent increase in [Ca2+]i,which was blocked by the cADPR receptor antagonist 8-amino-cADPR (20 µM) and by the RyR blockers ruthenium red (10 µM) and ryanodine (10 µM), but not by the inositol 1,4,5-trisphosphate receptor blockerheparin (0.5 mg/ml). During steady-state[Ca2+]ioscillations induced by acetylcholine (ACh), addition of 100 nM and 1 µM cADPR increased oscillation frequency and decreased peak-to-troughamplitude. ACh-induced[Ca2+]ioscillations were blocked by 8-amino-cADPR; however, 8-amino-cADPR didnot block the[Ca2+]iresponse to a subsequent exposure to caffeine. These results indicatethat cADPR acts as a second messenger forCa2+ release through RyR channelsin TSM cells and may be necessary for initiating ACh-induced[Ca2+]ioscillations. 相似文献
16.
Conceicao Isaltino M.; Lebrun Ivo; Cano-Abad Maria; Gandia Luis; Hernandez-Guijo Jesus M.; Lopez Manuela G.; Villarroya Mercedes; Jurkiewicz Aron; Garcia Antonio G. 《American journal of physiology. Cell physiology》1998,274(6):C1745
Toxin- (T)from the Brazilian scorpion Tityusserrulatus venom caused a concentration- andtime-dependent increase in the release of norepinephrine andepinephrine from bovine adrenal medullary chromaffin cells. T was~200-fold more potent than veratridine judged fromEC50 values, although the maximalsecretory efficacy of veratridine was 10-fold greater than that of T(1.2 vs. 12 µg/ml of catecholamine release). The combination of both toxins produced a synergistic effect that was particularly drastic at 5 mM extracellular Ca2+concentration([Ca2+]o),when 30 µM veratridine plus 0.45 µM T were used. T (0.45 µM) doubled the basal uptake of45Ca2+,whereas veratridine (100 µM) tripled it. Again, a drastic synergism in enhancing Ca2+ entry was seenwhen T and veratridine were combined; this was particularlypronounced at 5 mM[Ca2+]o.Veratridine induced oscillations of cytosolicCa2+ concentration([Ca2+]i)in single fura 2-loaded cells without elevation of basal levels. Incontrast, T elevated basal[Ca2+]ilevels, causing only small oscillations. When added together, T andveratridine elevated the basal levels of[Ca2+]iwithout causing large oscillations. T shifted the current-voltage (I-V) curve forNa+ channel current to the left.The combination of T with veratridine increased the shift of theI-V curve to the left, resulting in agreater recruitment of Na+channels at more hyperpolarizing potentials. This led to enhanced andmore rapid accumulation of Na+ inthe cell, causing cell depolarization, the opening of voltage-dependent Ca2+ channels, andCa2+ entry and secretion. 相似文献
17.
Huang L Bhattacharjee A Taylor JT Zhang M Keyser BM Marrero L Li M 《American journal of physiology. Cell physiology》2004,286(2):C213-C221
Chronic exposure of pancreatic -cells to high concentrations of glucose impairs the insulin secretory response to further glucose stimulation. This phenomenon is referred to as glucose desensitization. It has been shown that glucose desensitization is associated with abnormal elevation of -cell basal intracellular free Ca2+ concentration ([Ca2+]i). We have investigated the relationship between the basal intracellular free Ca2+ and the L-type (Cav1.3) Ca2+ channel translocation in insulin-secreting cells. Glucose stimulation or membrane depolarization induced a nifedipine-sensitive Ca2+ influx, which was attenuated when the basal [Ca2+]i was elevated. Using voltage-clamp techniques, we found that changing [Ca2+]i could regulate the amplitude of the Ca2+ current. This effect was attenuated by drugs that interfere with the cytoskeleton. Immunofluorescent labeling of Cav1.3 showed an increase in the cytoplasmic distribution of the channels under high [Ca2+]i conditions by deconvolution microscopy. The [Ca2+]i-dependent translocation of Cav1.3 channel was also demonstrated by Western blot analysis of biotinylation/NeutrAvidin-bead-eluted surface proteins in cells preincubated at various [Ca2+]i. These results suggest that Cav1.3 channel trafficking is involved in glucose desensitization of pancreatic -cells. internalization; intracellular free calcium; glucose desensitization 相似文献
18.
Effect of beta -adrenoceptor activation on [Ca2+]i regulation in murine skeletal myotubes 总被引:1,自引:0,他引:1
Prakash Y. S.; van der Heijden H. F.M.; Gallant E. M.; Sieck G. C. 《American journal of physiology. Cell physiology》1999,276(5):C1038
The presentstudy used real-time confocal microscopy to examine the effects of the2-adrenoceptor agonistsalbutamol on regulation of intracellularCa2+ concentration([Ca2+]i)in myotubes derived from neonatal mouse limb muscles.Immunocytochemical staining for ryanodine receptors and skeletal musclemyosin confirmed the presence of sarcomeres. The myotubes displayedboth spontaneous and ACh-induced rapid (<2-ms rise time)[Ca2+]itransients. The[Ca2+]itransients were frequency modulated by both low and high concentrations of salbutamol. Exposure to -bungarotoxin and tetrodotoxin inhibited ACh-induced[Ca2+]itransients and the response to low concentrations of salbutamol but notthe response to higher concentrations. Preexposure to caffeineinhibited the subsequent[Ca2+]iresponse to lower concentrations of salbutamol and significantly blunted the response to higher concentrations. Preexposure to salbutamol diminished the[Ca2+]iresponse to caffeine. Inhibition of dihydropyridine-sensitive Ca2+ channels with nifedipine orPN-200-110 did not prevent[Ca2+]ielevations induced by higher concentrations of salbutamol. The effectsof salbutamol were mimicked by the membrane-permeant analog dibutyryladenosine 3',5'-cyclic monophosphate. Thesedata indicate that salbutamol effects in skeletal muscle predominantly involve enhanced sarcoplasmic reticulumCa2+ release. 相似文献
19.
EGF inhibits muscarinic receptor-mediated calcium signaling in a human salivary cell line 总被引:1,自引:0,他引:1
Zhang BX Yeh CK Hymer TK Lifschitz MD Katz MS 《American journal of physiology. Cell physiology》2000,279(4):C1024-C1033
The effects of epidermal growth factor(EGF) on intracellular calcium ([Ca2+]i)responses to the muscarinic agonist carbachol were studied in a humansalivary cell line (HSY). Carbachol (104 M)-stimulated[Ca2+]i mobilization was inhibited by 40%after 48-h treatment with 5 × 1010 M EGF. EGF alsoreduced carbachol-induced [Ca2+]i inCa2+-free medium and Ca2+ influx followingrepletion of extracellular Ca2+. UnderCa2+-free conditions, thapsigargin, an inhibitor ofCa2+ uptake to internal stores, induced similar[Ca2+]i signals in control and EGF-treatedcells, indicating that internal Ca2+ stores were unaffectedby EGF; however, in cells exposed to thapsigargin, Ca2+influx following Ca2+ repletion was reduced by EGF.Muscarinic receptor density, assessed by binding of the muscarinicreceptor antagonistL-[benzilic-4,4'-3HCN]quinuclidinyl benzilate([3H]QNB), was decreased by 20% after EGF treatment.Inhibition of the carbachol response by EGF was not altered by phorbolester-induced downregulation of protein kinase C (PKC) but was enhancedupon PKC activation by a diacylglycerol analog. Phosphorylation of mitogen-activated protein kinase (MAP kinase) and inhibition of thecarbachol response by EGF were both blocked by the MAP kinase pathwayinhibitor PD-98059. The results suggest that EGF decreases carbachol-induced Ca2+ release from internal stores andalso exerts a direct inhibitory action on Ca2+ influx. Adecline in muscarinic receptor density may contribute to EGF inhibitionof carbachol responsiveness. The inhibitory effect of EGF is mediatedby the MAP kinase pathway and is potentiated by a distinct modulatorycascade involving activation of PKC. EGF may play a physiological rolein regulating muscarinic receptor-stimulated salivary secretion. 相似文献
20.
Ciglitizone inhibits cell proliferation in human uterine leiomyoma via activation of store-operated Ca2+ channels 总被引:1,自引:0,他引:1
Kim BY Cho CH Song DK Mun KC Suh SI Kim SP Shin DH Jang BC Kwon TK Cha SD Bae I Bae JH 《American journal of physiology. Cell physiology》2005,288(2):C389-C395
This study investigated the acute effects of a peroxisome proliferator-activated receptor (PPAR)- ligand, ciglitizone, on cell proliferation and intracellular Ca2+ signaling in human normal myometrium and uterine leiomyoma. Changes in intracellular Ca2+ concentration ([Ca2+]i) were measured with fura-2 AM, and cellular viabilities were determined by viable cell count and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide reduction assay. Ciglitizone (100 µM) induced greater inhibition of cell proliferation in uterine leiomyoma than in myometrium. Ciglitizone also dose-dependently increased [Ca2+]i in both myometrium and uterine leiomyoma; these [Ca2+]i increases were inhibited by PPAR- antagonists and raloxifene. Ciglitizone-induced [Ca2+]i increase showed only an initial peak in normal myometrial cells, whereas in uterine leiomyoma there was a second sustained [Ca2+]i increase as well. The initial [Ca2+]i increase in both myometrium and uterine leiomyoma resulted from the release of Ca2+ by the sarcoplasmic reticulum via activation of ryanodine receptors. The second [Ca2+]i increase was observed only in uterine leiomyoma because of a Ca2+ influx via an activation of store-operated Ca2+ channels (SOCCs). Cell proliferation was inhibited and secondary [Ca2+]i increase in uterine leiomyoma was attenuated by cotreatment of ciglitizone with a SOCC blocker, lanthanum. The results suggest that ciglitizone inhibits cell proliferation and increases [Ca2+]i through the activation of SOCCs, especially in human uterine leiomyoma. peroxisome proliferator-activated receptor-; intracellular calcium; uterine cells 相似文献