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1.
Intracellular Ca(2+) stores in chemoreceptor cells of the rabbit carotid body: significance for chemoreception 总被引:1,自引:0,他引:1
Vicario I Obeso A Rocher A López-Lopez JR González C 《American journal of physiology. Cell physiology》2000,279(1):C51-C61
Thenotion that intracellular Ca2+ (Cai2+)stores play a significant role in the chemoreception process inchemoreceptor cells of the carotid body (CB) appears in the literaturein a recurrent manner. However, the structural identity of theCa2+ stores and their real significance in the function ofchemoreceptor cells are unknown. To assess the functional significanceof Cai2+ stores in chemoreceptor cells, we havemonitored 1) the release of catecholamines (CA) from thecells using an in vitro preparation of intact rabbit CB and2) the intracellular Ca2+ concentration([Ca2+]i) using isolated chemoreceptor cells;both parameters were measured in the absence or the presence of agentsinterfering with the storage of Ca2+. We found thatthreshold [Ca2+]i for high extracellularK+ (Ke+) to elicit a release response is250 nM. Caffeine (10-40 mM), ryanodine (0.5 µM), thapsigargin(0.05-1 µM), and cyclopiazonic acid (10 µM) did not alter thebasal or the stimulus (hypoxia, high Ke+)-inducedrelease of CA. The same agents produced Cai2+transients of amplitude below secretory threshold; ryanodine (0.5 µM), thapsigargin (1 µM), and cyclopiazonic acid (10 µM) did notalter the magnitude or time course of the Cai2+responses elicited by high Ke+. Several potentialactivators of the phospholipase C system (bethanechol, ATP, andbradykinin), and thereby of inositol 1,4,5-trisphosphate receptors,produced minimal or no changes in [Ca2+]i anddid not affect the basal release of CA. It is concluded that, in therabbit CB chemoreceptor cells, Cai2+ stores do not playa significant role in the instant-to-instant chemoreception process. 相似文献
2.
Jean K Bernatchez G Klein H Garneau L Sauvé R Parent L 《American journal of physiology. Cell physiology》2002,282(4):C665-C672
The Ca2+ affinity andpermeation of the epithelial Ca2+ channel (ECaC1) wereinvestigated after expression in Xenopus oocytes. ECaC1displayed anomalous mole-fraction effects. Extracellular Ca2+ and Mg2+ reversibly inhibited ECaC1 wholecell Li+ currents: IC50 = 2.2 ± 0.4 µM (n = 9) and 235 ± 35 µM (n = 10), respectively. These values compare well with theCa2+ affinity of the L-type voltage-gated Ca2+(CaV1.2) channel measured under the same conditions,suggesting that high-affinity Ca2+ binding is awell-conserved feature of epithelial and voltage-gated Ca2+channels. Neutralization of D550 and E535 in the pore region had nosignificant effect on Ca2+ and Mg2+ affinities.In contrast, neutralization of D542 significantly decreasedCa2+ affinity (IC50 = 1.1 ± 0.2 mM,n = 6) and Mg2+ affinity(IC50 > 25 ± 3 mM, n = 4).Despite a 1,000-fold decrease in Ca2+ affinity in D542N,Ca2+ permeation properties and theCa2+-to-Ba2+ conductance ratio remainedcomparable to values for wild-type ECaC1. Together, our observationssuggest that D542 plays a critical role in Ca2+ affinitybut not in Ca2+ permeation in ECaC1. 相似文献
3.
Various mechanicalstimuli increase the intracellular Ca2+ concentration([Ca2+]i) in vascular smooth muscle cells(VSMC). A part of the increase in [Ca2+]i isdue to the release of Ca2+ from intracellular stores. Wehave investigated the effect of mechanical stimulation produced bycyclical stretch on the release of Ca2+ from theintracellular stores. Permeabilized VSMC loaded with 45Ca2+ were subjected to 7.5% average (15%maximal) cyclical stretch. This resulted in an increase in45Ca2+ rate constant by 0.126 ± 0.0035. Inhibition of inositol 1,4,5-trisphosphate (IP3),ryanodine, and nicotinic acid adenine dinucleotide phosphate channels(NAADP) with 50 µg/ml heparin, 50 µM ruthenium red, and 25 µMthio-NADP, respectively, did not block the increase in45Ca2+ efflux in response to cyclical stretch.However, 10 µM lanthanum, 10 µM gadolinium, and 10 µMcytochalasin D but not 10 µM nocodazole inhibited the increase in45Ca2+ efflux. This supports the existence of anovel stretch-sensitive intracellular Ca2+ store in VSMCthat is distinct from the IP3-, ryanodine-, and NAADP-sensitive stores. 相似文献
4.
Mohanty Madhumita Jena; Ye Maian; Li Xingli; Rossi Noreen F. 《American journal of physiology. Cell physiology》2001,281(2):C555
Hypotonicswelling increases the intracellular Ca2+ concentration([Ca2+]i) in vascular smooth muscle cells(VSMC). The source of this Ca2+ is not clear. To study thesource of increase in [Ca2+]i in response tohypotonic swelling, we measured [Ca2+]i infura 2-loaded cultured VSMC (A7r5 cells). Hypotonic swelling produced a40.7-nM increase in [Ca2+]i that was notinhibited by EGTA but was inhibited by 1 µM thapsigargin. Priordepletion of inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ stores with vasopressin did not inhibit the increasein [Ca2+]i in response to hypotonic swelling.Exposure of 45Ca2+-loaded intracellular storesto hypotonic swelling in permeabilized VSMC produced an increase in45Ca2+ efflux, which was inhibited by 1 µMthapsigargin but not by 50 µg/ml heparin, 50 µM ruthenium red, or25 µM thio-NADP. Thus hypotonic swelling of VSMC causes a release ofCa2+ from the intracellular stores from a novel sitedistinct from the IP3-, ryanodine-, and nicotinic acidadenine dinucleotide phosphate-sensitive stores. 相似文献
5.
Thrombin-, bradykinin-, and arachidonic acid-induced Ca2+ signaling in Ehrlich ascites tumor cells 总被引:1,自引:0,他引:1
Jorgensen Nanna Koschmieder; Petersen Stine Falsig; Hoffmann Else Kay 《American journal of physiology. Cell physiology》1999,276(1):C26
Stimulation ofsingle Ehrlich ascites tumor cells with agonists (bradykinin, thrombin)and with arachidonic acid (AA) induces increases in the freeintracellular Ca2+ concentration([Ca2+]i)in the presence and absence of extracellularCa2+, measured using theCa2+-sensitive probe fura 2. Sequential stimulation with two agonists elicits sequential increasesin[Ca2+]i,unlike addition of the same agonist twice. Bradykinin and thrombin haveadditive effects on[Ca2+]iin Ca2+-free medium. Thephosphoinositidase C inhibitor U-73122 inhibits the agonist-inducedincreases in[Ca2+]i,whereas ryanodine has no effect. Pretreatment of cells in Ca2+-free medium with thapsigarginabolishes the bradykinin-induced increase in[Ca2+]ibut not the response to thrombin. The AA-induced response is notinhibited by U-73122 and cannot be mimicked by the inactive structuralanalog trifluoromethylarachidonyl ketone. Pretreatment of the cellswith 50 µM AA (but not with 10 µM AA) abolishes the agonist-inducedincrease in[Ca2+]i.Thus bradykinin, thrombin, and AA induce increases in[Ca2+]iin Ehrlich cells due to Ca2+ entryand release from intracellular stores. Thrombin causes release ofCa2+ from an intracellular storethat is insensitive to bradykinin and is not depleted by thapsigarginbut is depleted by AA. 相似文献
6.
To investigatethe Ca2+-dependent plasticity ofsarcoplasmic reticulum (SR) function in vascular smooth muscle,transient responses to agents releasing intracellularCa2+ by either ryanodine(caffeine) orD-myo-inositol1,4,5-trisphosphate [IP3;produced in response to norepinephrine (NE),5-hydroxytryptamine (5-HT), arginine vasopressin (AVP)] receptorsin rat tail arterial rings were evaluated after 4 days of organculture. Force transients induced by all agents were increased comparedwith those induced in fresh rings. Stimulation by 10% FCSduring culture further potentiated the force andCa2+ responses to caffeine (20 mM)but not to NE (10 µM), 5-HT (10 µM), or AVP (0.1 µM). The effectwas persistent, and SR capacity was not altered after reversibledepletion of stores with cyclopiazonic acid. The effects of serum couldbe mimicked by culture in depolarizing medium (30 mMK+) and blocked by the additionof verapamil (1 µM) or EGTA (1 mM) to the medium, loweringintracellular Ca2+ concentration([Ca2+]i)during culture. These results show that modulation of SR function canoccur in vitro by a mechanism dependent on long-term levels of basal[Ca2+]iand involving ryanodine- but notIP3 receptor-mediatedCa2+release. 相似文献
7.
Gonzalez Antonio; Pfeiffer Fatima; Schmid Andreas; Schulz Irene 《American journal of physiology. Cell physiology》1998,275(3):C810
We have used fluo3-loaded mouse pancreatic acinar cells to investigate the relationshipbetween Ca2+ mobilization andintracellular pH (pHi). TheCa2+-mobilizing agonist ACh (500 nM) induced a Ca2+ release in theluminal cell pole followed by spreading of the Ca2+ signal toward the basolateralside with a mean speed of 16.1 ± 0.3 µm/s. In the presence of anacidic pHi, achieved by blockade of theNa+/H+exchanger or by incubation of the cells in aNa+-free buffer, a slowerspreading of ACh-evoked Ca2+ waveswas observed (7.2 ± 0.6 µm/s and 7.5 ± 0.3 µm/s,respectively). The effects of cytosolic acidification on thepropagation rate of ACh-evokedCa2+ waves were largely reversibleand were not dependent on the presence of extracellularCa2+. A reduction in the spreadingspeed of Ca2+ waves could also beobserved by inhibition of the vacuolarH+-ATPase with bafilomycinA1 (11.1 ± 0.6 µm/s), whichdid not lead to cytosolic acidification. In contrast, inhibition of theendoplasmic reticulum Ca2+-ATPaseby 2,5-di-tert-butylhydroquinone ledto faster spreading of the ACh-evokedCa2+ signals (25.6 ± 1.8 µm/s), which was also reduced by cytosolic acidification or treatmentof the cells with bafilomycin A1.Cytosolic alkalinization had no effect on the spreading speed of theCa2+ signals. The data suggestthat the propagation rate of ACh-induced Ca2+ waves is decreased byinhibition of Ca2+ release fromintracellular stores due to cytosolic acidification or toCa2+ pool alkalinizationand/or to a decrease in the proton gradient directed from theinositol 1,4,5-trisphosphate-sensitiveCa2+ pool to the cytosol. 相似文献
8.
Muscarinic stimulation increases basal Ca(2+) and inhibits spontaneous Ca(2+) transients in murine colonic myocytes 总被引:1,自引:0,他引:1
Bayguinov O Hagen B Sanders KM 《American journal of physiology. Cell physiology》2001,280(3):C689-C700
Localized Ca2+ transients inisolated murine colonic myocytes depend on Ca2+ releasefrom inositol 1,4,5-trisphosphate (IP3) receptors.Localized Ca2+ transients couple to spontaneous transientoutward currents (STOCs) and mediate hyperpolarization responses inthese cells. We used confocal microscopy and whole cell patch-clamprecording to investigate how muscarinic stimulation, which causesformation of IP3, can suppress Ca2+ transientsand STOCs that might override the excitatory nature of cholinergicresponses. ACh (10 µM) reduced localized Ca2+ transientsand STOCs, and these effects were associated with a rise in basalcytosolic Ca2+. These effects of ACh were mimicked bygeneralized rises in basal Ca2+ caused by ionomycin(250-500 nM) or elevated external Ca2+ (6 mM).Atropine (10 µM) abolished the effects of ACh. Pretreatment of cellswith nicardipine (1 µM), or Cd2+ (200 µM) had no effecton responses to ACh. An inhibitor of phospholipase C, U-73122, blockedCa2+ transients and STOCs but did not affect the increasein basal Ca2+ after ACh stimulation. Xestospongin C (Xe-C;5 µM), a membrane-permeable antagonist of IP3 receptors,blocked spontaneous Ca2+ transients but did not prevent theincrease of basal Ca2+ in response to ACh. Gd3+(10 µM), a nonselective cation channel inhibitor, prevented the increase in basal Ca2+ after ACh and increased thefrequency and amplitude of Ca2+ transients and waves.Another inhibitor of receptor-mediated Ca2+ influxchannels, SKF-96365, also prevented the rise in basal Ca2+after ACh and increased Ca2+ transients and development ofCa2+ waves. FK-506, an inhibitor ofFKBP12/IP3 receptor interactions, had no effect onthe rise in basal Ca2+ but blocked the inhibitory effectsof increased basal Ca2+ and ACh on Ca2+transients. These results suggest that the rise in basalCa2+ that accompanies muscarinic stimulation of colonicmuscles inhibits localized Ca2+ transients that couldcouple to activation of Ca2+-activated K+channels and reduce the excitatory effects of ACh. 相似文献
9.
L-type voltage-dependent Ca2+ channels in cerebral microvascular endothelial cells and ET-1 biosynthesis 总被引:2,自引:0,他引:2
We investigatedthe role of intracellular calcium concentration([Ca2+]i) in endothelin-1 (ET-1) production,the effects of potential vasospastic agents on[Ca2+]i, and the presence of L-typevoltage-dependent Ca2+ channels in cerebral microvascularendothelial cells. Primary cultures of endothelial cells isolated frompiglet cerebral microvessels were used. Confluent cells were exposed toeither the thromboxane receptor agonist U-46619 (1 µM),5-hydroxytryptamine (5-HT; 0.1 mM), or lysophosphatidic acid (LPA; 1 µM) alone or after pretreatment with the Ca2+-chelatingagent EDTA (100 mM), the L-type Ca2+ channel blockerverapamil (10 µM), or the antagonist of receptor-operated Ca2+ channel SKF-96365 HCl (10 µM) for 15 min. ET-1production increased from 1.2 (control) to 8.2 (U-46619), 4.9 (5-HT),or 3.9 (LPA) fmol/µg protein, respectively. Such elevated ET-1biosynthesis was attenuated by verapamil, EDTA, or SKF-96365 HCl. Toinvestigate the presence of L-type voltage-dependent Ca2+channels in endothelial cells, the [Ca2+]isignal was determined fluorometrically by using fura 2-AM. Superfusionof confluent endothelial cells with U-46619, 5-HT, or LPA significantlyincreased [Ca2+]i. Pretreatment ofendothelial cells with high K+ (60 mM) or nifedipine (4 µM) diminished increases in [Ca2+]i inducedby the vasoactive agents. These results indicate that 1)elevated [Ca2+]i signals are involved in ET-1biosynthesis induced by specific spasmogenic agents, 2) theincreases in [Ca2+]i induced by thevasoactive agents tested involve receptor as well as L-typevoltage-dependent Ca2+ channels, and 3) primarycultures of cerebral microvascular endothelial cells express L-typevoltage-dependent Ca2+ channels. 相似文献
10.
p38 mitogen-activated protein kinase inhibits calcium-dependent chloride secretion in T84 colonic epithelial cells 总被引:1,自引:0,他引:1
We havepreviously shown that Ca2+-dependent Clsecretion across intestinal epithelial cells is limited by a signalingpathway involving transactivation of the epidermal growth factorreceptor (EGFR) and activation of ERK mitogen-activated protein kinase (MAPK). Here, we have investigated a possible role for p38 MAPK inregulation of Ca2+-dependent Cl secretion.Western blot analysis of T84 colonic epithelial cells revealed that the muscarinic agonist carbachol (CCh; 100 µM)stimulated phosphorylation and activation of p38 MAPK. The p38inhibitor SB-203580 (10 µM) potentiated and prolonged short-circuitcurrent (Isc) responses to CCh acrossvoltage-clamped T84 cells to 157.4 ± 6.9% of thosein control cells (n = 21; P < 0.001).CCh-induced p38 phosphorylation was attenuated by the EGFR inhibitortyrphostin AG-1478 (0.1 nM-10 µM) and by the Src family kinaseinhibitor PP2 (20 nM-2 µM). The effects of CCh on p38phosphorylation were mimicked by thapsigargin (TG; 2 µM), whichspecifically elevates intracellular Ca2+, and wereabolished by the Ca2+ chelator BAPTA-AM (20 µM), implyinga role for intracellular Ca2+ in mediating p38 activation.SB-203580 (10 µM) potentiated Isc responses toTG to 172.4 ± 18.1% of those in control cells (n = 18; P < 0.001). When cells were pretreated withSB-203580 and PD-98059 to simultaneously inhibit p38 and ERK MAPKs,respectively, Isc responses to TG and CCh weresignificantly greater than those observed with either inhibitor alone.We conclude that Ca2+-dependent agonists stimulate p38 MAPKin T84 cells by a mechanism involving intracellularCa2+, Src family kinases, and the EGFR. CCh-stimulated p38activation constitutes a similar, but distinct and complementary,antisecretory signaling pathway to that of ERK MAPK. 相似文献
11.
Xu Xiaoping; Forrer Janet; Bechtel Peter J.; Best Philip M. 《American journal of physiology. Cell physiology》1998,274(4):C861
To determine theeffect of plasma growth hormone (GH) on skeletal muscle function, wemeasured the free Ca2+concentration-tension relationship of slow-twitch (soleus) and fast-twitch (peroneus longus) muscles isolated from rats undergoing acromegaly in response to implanted, GH-secreting tumors. Muscles fromadult (9 mo) and aged rats (24 mo) were studied after the tumor-bearingrats weighed over 50% more than their age-matched controls.Ca2+-activated isometric tensionwas recorded from skinned muscle fibers. For soleus muscles, the freeCa2+ concentration producing 50%of maximal tension([Ca2+]50)was 2.0 µM for rats with tumors and 3.4-3.6 µM for controls. For peroneus longus fibers,[Ca2+]50shifted from 6.1-6.7 µM in controls to 3.5 µM after tumors were introduced into either adult or aged rats. Soleus muscle fibersfrom neonatal rats (14 days) were less sensitive toCa2+ than those isolated fromadult rats, having a[Ca2+]50of 7.3 µM. The Ca2+ sensitivityof peroneus longus fibers did not change with age. We conclude thatsignificant increases in myofibrillarCa2+ sensitivity occur in skeletalmuscles undergoing rapid growth induced by GH-secreting tumors. 相似文献
12.
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
13.
Lax A Soler F Fernandez-Belda F 《American journal of physiology. Cell physiology》2002,283(1):C85-C92
The inhibition of sarcoplasmic reticulumCa2+-ATPase activity by miconazole was dependent on theconcentration of ATP and membrane protein. Half-maximal inhibition wasobserved at 12 µM miconazole when the ATP concentration was 50 µMand the membrane protein was 0.05 mg/ml. When ATP was 1 mM, a lowmicromolar concentration of miconazole activated the enzyme, whereashigher concentrations inhibited it. A qualitatively similar responsewas observed when Ca2+ transport was measured. Likewise,the half-maximal inhibition value was higher when the membraneconcentration was raised. Phosphorylation studies carried out aftersample preequilibration in different experimental settings shed lighton key partial reactions such as Ca2+ binding and ATPphosphorylation. The miconazole effect on Ca2+-ATPaseactivity can be attributed to stabilization of theCa2+-free enzyme conformation giving rise to a decrease inthe rate of the Ca2+ binding transition. The phosphoryltransfer reaction was not affected by miconazole. 相似文献
14.
The Ca2+-sensing receptor: a target for polyamines 总被引:1,自引:0,他引:1
Quinn Stephen J.; Ye Chian-Ping; Diaz Rubin; Kifor Olga; Bai Mei; Vassilev Peter; Brown Edward 《American journal of physiology. Cell physiology》1997,273(4):C1315
The Ca2+-sensing receptor(CaR) is activated at physiological levels of externalCa2+(Cao) but is expressed in anumber of tissues that do not have well-established roles in thecontrol of Cao, including several regions of the brain and the intestine. Polyamines are endogenous polyvalent cations that can act as agonists for the CaR, as shown byour current studies of human embryonic kidney (HEK-293) cells transfected with the human CaR. Cellular parameters altered by polyamines included cytosolic freeCa2+(Cai), inositol phosphateproduction, and the activity of a nonselective cation channel. Sperminestimulated Cai transients inCaR-transfected HEK cells, with a concentration producing ahalf-maximal response (EC50) of ~500µM in the presence of 0.5 mMCa2+, whereas sustained increasesin Cai had anEC50 of ~200 µM. The order ofpotency was spermine > spermidine >> putrescine. Elevation ofCao shifted theEC50 for spermine sharply to theleft, with substantial stimulation below 100 µM. Addition ofsubthreshold concentrations of spermine increased the sensitivity ofCaR-expressing HEK cells to Cao.Parathyroid hormone secretion from bovine parathyroid cells wasinhibited by 50% in the presence of 200 µM spermine, a responsesimilar to that elicited by 2.0 mMCao. These data suggest thatpolyamines could be effective agonists for the CaR, and severaltissues, including the brain, may use the CaR as a target for theactions of spermine and other endogenous polycationic agonists. 相似文献
15.
Ca2+ and protein kinase C activation of mucin granule exocytosis in permeabilized SPOC1 cells 总被引:2,自引:0,他引:2
Scott C. E.; Abdullah Lubna H.; Davis C. William 《American journal of physiology. Cell physiology》1998,275(1):C285
Mucin secretion by airway goblet cells is under the control ofapical P2Y2, phospholipaseC-coupled purinergic receptors. In SPOC1 cells, the mobilization ofintracellular Ca2+ by ionomycin orthe activation of protein kinase C (PKC) by phorbol 12-myristate13-acetate (PMA) stimulates mucin secretion in a fully additive fashion[L. H. Abdullah, J. D. Conway, J. A. Cohn, and C. W. Davis.Am. J. Physiol. 273 (Lung Cell. Mol. Physiol. 17):L201-L210, 1997]. This apparent independence between PKC andCa2+ in the stimulation of mucinsecretion was tested in streptolysin O-permeabilized SPOC1 cells. Thesecells were fully competent to secrete mucin whenCa2+ was elevated from 100 nM to3.1 µM for 2 min following permeabilization; theCa2+EC50 was 2.29 ± 0.07 µM.Permeabilized SPOC1 cells were exposed to PMA or 4-phorbol atCa2+ activities ranging from 10 nMto 10 µM. PMA, but not 4-phorbol, increased mucin release at allCa2+ activities tested: at 10 nMCa2+ mucin release was 2.1-foldgreater than control and at 4.7 µM Ca2+ mucin release was maximal(3.6-fold increase). PMA stimulated 27% more mucin release at 4.7 µMthan at 10 nM Ca2+. Hence, SPOC1cells possess Ca2+-insensitive,PKC-dependent, and Ca2+-dependentPKC-potentiated pathways for mucin granule exocytosis. 相似文献
16.
Murthy Karnam S.; Makhlouf Gabriel M. 《American journal of physiology. Cell physiology》1998,274(5):C1199
Recent studies on the role of nitric oxide (NO) ingastrointestinal smooth muscle have raised the possibility thatNO-stimulated cGMP could, in the absence of cGMP-dependent proteinkinase (PKG) activity, act as aCa2+-mobilizing messenger[K. S. Murthy, K.-M. Zhang, J.-G. Jin, J. T. Grider, and G. M. Makhlouf. Am. J. Physiol. 265 (Gastrointest. Liver Physiol. 28):G660-G671, 1993]. This notion was examined indispersed gastric smooth muscle cells with 8-bromo-cGMP (8-BrcGMP) andwith NO and vasoactive intestinal peptide (VIP), which stimulate endogenous cGMP. In muscle cells treated with cAMP-dependent protein kinase (PKA) and PKG inhibitors (H-89 and KT-5823), 8-BrcGMP (10 µM),NO (1 µM), and VIP (1 µM) stimulated45Ca2+release (21 ± 3 to 30 ± 1% decrease in45Ca2+cell content); Ca2+ releasestimulated by 8-BrcGMP was concentration dependent with anEC50 of 0.4 ± 0.1 µM and athreshold of 10 nM. 8-BrcGMP and NO increased cytosolic freeCa2+ concentration([Ca2+]i)and induced contraction; both responses were abolished after Ca2+ stores were depleted withthapsigargin. With VIP, which normally increases[Ca2+]iby stimulating Ca2+ influx,treatment with PKA and PKG inhibitors caused a further increase in[Ca2+]ithat reverted to control levels in cells pretreated with thapsigargin. Neither Ca2+ release norcontraction induced by cGMP and NO in permeabilized muscle cells wasaffected by heparin or ruthenium red.Ca2+ release induced by maximallyeffective concentrations of cGMP and inositol 1,4,5-trisphosphate(IP3) was additive, independent of which agent was applied first. We conclude that, in the absence ofPKA and PKG activity, cGMP stimulatesCa2+ release from anIP3-insensitive store and that itseffect is additive to that of IP3. 相似文献
17.
Gomora Juan Carlos; Enyeart John J. 《American journal of physiology. Cell physiology》1998,275(6):C1526
Bovine adrenalzona fasciculata cells (AZF) express a noninactivatingK+ current(IAC) whoseinhibition by adrenocorticotropic hormone and ANG II may be coupled tomembrane depolarization andCa2+-dependentcortisol secretion. We studiedIACinhibition byCa2+ and theCa2+ionophore ionomycin in whole cell and single-channel patch-clamp recordings of AZF. In whole cell recordings with intracellular (pipette)Ca2+concentration([Ca2+]i)buffered to 0.02 µM,IAC reachedmaximum current density of 25.0 ± 5.1 pA/pF(n = 16); raising[Ca2+]ito 2.0 µM reduced it 76%. In inside-out patches, elevated[Ca2+]idramatically reducedIAC channelactivity. Ionomycin inhibited IAC by 88 ± 4% (n = 14) without altering rapidlyinactivating A-type K+ current.Inhibition of IACby ionomycin was unaltered by adding calmodulin inhibitory peptide tothe pipette or replacing ATP with its nonhydrolyzable analog5'-adenylylimidodiphosphate.IAC inhibition byionomycin was associated with membrane depolarization. When[Ca2+]iwas buffered to 0.02 µM with 2 and 11 mM1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), ionomycin inhibitedIAC by 89.6 ± 3.5 and 25.6 ± 14.6% and depolarized the same AZF by 47 ± 8 and 8 ± 3 mV, respectively (n = 4). ANG II inhibitedIAC significantlymore effectively when pipette BAPTA was reduced from 11 to 2 mM. Raising[Ca2+]iinhibits IACthrough a mechanism not requiring calmodulin or protein kinases,suggesting direct interaction withIAC channels. ANGII may inhibitIAC anddepolarize AZF by activating parallel signaling pathways, one of whichuses Ca2+ asa mediator. 相似文献
18.
We examined the effects of dissolved nitric oxide (NO) gas oncytoplasmic calcium levels ([Ca2+]i) in C6glioma cells under anoxic conditions. The maximum elevation (27 ± 3 nM) of [Ca2+]i was reached at 10 µM NO. Asecond application of NO was ineffective if the first was >0.5 µM.The NO donor diethylamine/NO mimicked the effects of NO. Acute exposureof the cells to low calcium levels was without effect on the NO-evokedresponse. Thapsigargin (TG) increased [Ca2+]iand was less effective if cells were pretreated with NO. Hemoglobin inhibited the effects of NO at a molar ratio of 10:1. 8-Bromo-cGMP waswithout effect on the NO-evoked response. If cells were pretreated withTG or exposed chronically to nominal amounts of calcium, NO decreased[Ca2+]i. The results suggest that C6 gliomacells have two receptors for NO. One receptor (NOA)elevates [Ca2+]i and resides on theendoplasmic reticulum (ER). The other receptor (NOB)decreases [Ca2+]i and resides on theplasmalemma or the ER. The latter receptor dominates when the level ofcalcium within intracellular stores is diminished. 相似文献
19.
In fura 2-loaded N1E-115 cells, regulationof intracellular Ca2+ concentration([Ca2+]i) following a Ca2+ loadinduced by 1 µM thapsigargin and 10 µM carbonylcyanidep-trifluoromethyoxyphenylhydrazone (FCCP) wasNa+ dependent and inhibited by 5 mM Ni2+. Incells with normal intracellular Na+ concentration([Na+]i), removal of bath Na+,which should result in reversal of Na+/Ca2+exchange, did not increase [Ca2+]i unlesscell Ca2+ buffer capacity was reduced. When N1E-115 cellswere Na+ loaded using 100 µM veratridine and 4 µg/mlscorpion venom, the rate of the reverse mode of theNa+/Ca2+ exchanger was apparently enhanced,since an ~4- to 6-fold increase in [Ca2+]ioccurred despite normal cell Ca2+ buffering. In SBFI-loadedcells, we were able to demonstrate forward operation of theNa+/Ca2+ exchanger (net efflux ofCa2+) by observing increases (~ 6 mM) in[Na+]i. These Ni2+ (5 mM)-inhibited increases in [Na+]i could onlybe observed when a continuous ionomycin-induced influx ofCa2+ occurred. The voltage-sensitive dyebis-(1,3-diethylthiobarbituric acid) trimethine oxonol was used tomeasure changes in membrane potential. Ionomycin (1 µM) depolarizedN1E-115 cells (~25 mV). This depolarization was Na+dependent and blocked by 5 mM Ni2+ and 250-500 µMbenzamil. These data provide evidence for the presence of anelectrogenic Na+/Ca2+ exchanger that is capableof regulating [Ca2+]i after release ofCa2+ from cell stores. 相似文献
20.
Effects of estradiol on phenylephrine contractility associated with intracellular calcium release in rat aorta 总被引:1,自引:0,他引:1
Castillo C Ceballos G Rodríguez D Villanueva C Medina R López J Méndez E Castillo EF 《American journal of physiology. Cell physiology》2006,291(6):C1388-C1394
The ability of estradiol to affect phenylephrine-induced contraction and the subsequent increase in resting tone, associated with capacitative Ca2+ entry across the plasma membrane, was evaluated in rat aortic rings incubated in Ca2+-free solution. The incubation with estradiol (1100 nM, 5 min) inhibited both the phenylephrine-induced contraction and the IRT. Neither cycloheximide (1 µM; inhibitor of protein synthesis) nor tamoxifen (1 µM; blocker of estrogenic receptors) modified the effects of estradiol. Estradiol (100 µM) also blocked the contractile response to serotonin (10 µM) but not to caffeine (10 mM). In addition, estradiol (100 µM) inhibited the contractile responses to cyclopiazonic acid (1 µM; selective Ca2+-ATPase inhibitor) associated with capacitative Ca2+ influx through non-L-type Ca2+ channels. Finally, estradiol inhibited the Ca2+-induced increases in intracellular free Ca2+ (after pretreatment with phenylephrine) in cultured rat aorta smooth muscle cells incubated in Ca2+-free solution. In conclusion, estradiol interfered in a concentration-dependent manner with Ca2+-dependent contractile effects mediated by the stimuli of 1-adrenergic and serotonergic receptors and inhibited the capacitative Ca2+ influx through both L-type and non-L-type Ca2+ channels. Such effects are in essence nongenomic and not mediated by the intracellular estrogenic receptor. estrogen; 1-adrenergic agonists 相似文献