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1.
Longitudinal smooth muscle strips from guinea pig ileum werecultured in vitro for 5 days, and the relationship betweenextracellular Ca2+ and force inhigh-K+ medium was evaluated. Instrips cultured with 10% fetal calf serum (FCS), this relationship wasshifted to the right (50% effective concentration changed by 2-3mM) compared with strips cultured without FCS. The shiftwas prevented by inclusion of verapamil (1 µM) during culture andmimicked by ionomycin in the absence of FCS. The intracellularCa2+ concentration([Ca2+]i)during stimulation with high-K+solution or carbachol was reduced after culture with FCS, whereas the[Ca2+]i-forcerelationship was unaffected. Cells were isolated from cultured strips,and whole cell voltage-clamp experiments were performed. Maximum inwardCa2+ current (10 mMBa2+), normalized to cellcapacitance, was almost three times smaller in cells isolated fromstrips cultured with FCS. Culture with 1 µM verapamil prevented thisreduction. These results suggest that increased[Ca2+]iduring culture downregulates Ca2+current density, with associated effects on contractility. 相似文献
2.
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
3.
Prakash Y. S.; Van Der Heijden H. F.M.; Kannan M. S.; Sieck G. C. 《Journal of applied physiology》1997,82(6):1836-1843
Prakash, Y. S., H. F. M. van der Heijden, M. S. Kannan, andG. C. Sieck. Effects of salbutamol on intracellular calcium oscillations in porcine airway smooth muscle. J. Appl.Physiol. 82(6): 1836-1843, 1997.Relaxation ofairway smooth muscle (ASM) by -adrenoceptor agonists involvesreduction of intracellular Ca2+concentration([Ca2+]i).In porcine ASM cells, acetylcholine induces[Ca2+]ioscillations that display frequency modulation by agonist concentration and basal[Ca2+]i.We used real-time confocal microscopy to examine the effect ofsalbutamol (1 nM to 1 µM), a2-adrenoceptor agonist, on[Ca2+]ioscillations in freshly dissociated porcine ASM cells. Salbutamol decreased the frequency of[Ca2+]ioscillations in a concentration-dependent fashion, completely inhibiting the oscillations at 1 µM. These effects were mimicked by acell-permeant analog of adenosine 3,5-cyclicmonophosphate. The inhibitory effect of salbutamol was partiallyreversed by BAY K 8644. Salbutamol reduced[Ca2+]ieven when sarcoplasmic reticulum (SR)Ca2+ reuptake andCa2+ influx were blocked.Lanthanum blockade of Ca2+ effluxattenuated the inhibitory effect of salbutamol on[Ca2+]i.The[Ca2+]iresponse to caffeine was unaffected by salbutamol. On the basis ofthese results, we conclude that2-adrenoceptor agonists have little effect on SR Ca2+ releasein ASM cells but reduce[Ca2+]iby inhibiting Ca2+ influx throughvoltage-gated channels and by enhancingCa2+ efflux. 相似文献
4.
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
5.
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
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.
To study the effects of flow on in situendothelial intracellular calcium concentration([Ca2+]i) signaling, rat aortic rings wereloaded with fura 2, mounted on a tissue flow chamber, and divided intocontrol and flow-pretreated groups. The latter was perfused with bufferat a shear stress of 50 dyns/cm2 for 1 h. Endothelial[Ca2+]i responses to ACh or shear stresseswere determined by ratio image analysis. Moreover, ACh-induced[Ca2+]i elevation responses were measured ina calcium-free buffer, or in the presence of SKF-96365, to elucidatethe role of calcium influx in the flow effects. Our results showed that1) ACh increased endothelial[Ca2+]i in a dose-dependent manner, and theseresponses were incremented by flow-pretreatment; 2) thedifferences in ACh-induced [Ca2+]i elevationbetween control and flow-pretreated groups were abolished by SKF-96365or by Ca2+-free buffer; and 3) in the presenceof 105 M ATP, shear stress induced dose-dependent[Ca2+]i elevation responses that were notaltered by flow-pretreatment. In conclusion, flow-pretreatment augmentsthe ACh-induced endothelial calcium influx in rat aortas ex vivo. 相似文献
8.
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
9.
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
10.
Suzuki Hideaki; Ikeda Katsuhisa; Furukawa Masayuki; Takasaka Tomonori 《American journal of physiology. Cell physiology》1997,273(5):C1533
The biological characteristics of the globular substance, aprecursor of otoconia, are unclear. In the present study, the ATP-induced internal free Ca2+ concentration([Ca2+]i) changes of the globular substanceand the ATP distribution in the vestibular organ were investigatedusing a Ca2+ indicator, fluo 3, and an adeninenucleotide-specific fluorochrome, quinacrine, by means of confocallaser scanning microscopy. [Ca2+]i showed arapid and dose-dependent increase in response to ATP with a 50%effective concentration (EC50) of 16.7 µM. Thisreaction was independent of external Ca2+, indicating thepresence of an internal Ca2+ reservoir. Neither adenosine,,-methylene-ATP, 3'-O-(4-benzoylbenzoyl)-ATP, ADP, norUTP evoked this reaction, whereas 2-methylthio-ATP induced an increaseof [Ca2+]i with an EC50 of 14.4 µM. Moreover, P2 antagonists, reactive blue 2 and suramin, and aphospholipase C inhibitor, U-73122, inhibited the ATP-induced[Ca2+]i increase. These findings indicate thepresence of a P2Y purinoceptor on the globular substance. In addition,granular fluorescence was observed in the quinacrine-stained macularsensory epithelium, indicating the presence of ATP-containing granulesin this tissue. These results suggest that a paracrine mechanisminvolving ATP may exist in the macula and that this mechanism regulatesthe biological behavior of the globular substance. 相似文献
11.
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
12.
Na(+)/Ca(2+) exchange and its role in intracellular Ca(2+) regulation in guinea pig detrusor smooth muscle 总被引:3,自引:0,他引:3
The role of Na+/Ca2+ exchange inregulating intracellular Ca2+ concentration([Ca2+]i) in isolated smooth muscle cellsfrom the guinea pig urinary bladder was investigated. Incrementalreduction of extracellular Na+ concentration resulted in agraded rise of [Ca2+]i; 50-100 µMstrophanthidin also increased [Ca2+]i. Asmall outward current accompanied the rise of[Ca2+]i in low-Na+ solutions(17.1 ± 1.8 pA in 29.4 mM Na+). The quantity ofCa2+ influx through the exchanger was estimated from thecharge carried by the outward current and was ~30 times that which isnecessary to account for the rise of [Ca2+]i,after correction was made for intracellular Ca2+ buffering.Ca2+ influx through the exchanger was able to loadintracellular Ca2+ stores. It is concluded that the levelof resting [Ca2+]i is not determined by theexchanger, and under resting conditions (membrane potential 50 to60 mV), there is little net flux through the exchanger. However, asmall rise of intracellular Na+ concentration would besufficient to generate significant net Ca2+ influx. 相似文献
13.
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
14.
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
15.
Zhang F Zhang Q Tengholm A Sjöholm A 《American journal of physiology. Cell physiology》2006,291(3):C466-C475
We previously reported that human growth hormone (hGH) increases cytoplasmic Ca2+ concentration ([Ca2+]i) and proliferation in pancreatic -cells (Sjöholm Å, Zhang Q, Welsh N, Hansson A, Larsson O, Tally M, and Berggren PO. J Biol Chem 275: 2103321040, 2000) and that the hGH-induced rise in [Ca2+]i involves Ca2+-induced Ca2+ release facilitated by tyrosine phosphorylation of ryanodine receptors (Zhang Q, Kohler M, Yang SN, Zhang F, Larsson O, and Berggren PO. Mol Endocrinol 18: 16581669, 2004). Here we investigated the tyrosine kinases that convey the hGH-induced rise in [Ca2+]i and insulin release in BRIN-BD11 -cells. hGH caused tyrosine phosphorylation of Janus kinase (JAK)2 and c-Src, events inhibited by the JAK2 inhibitor AG490 or the Src kinase inhibitor PP2. Although hGH-stimulated rises in [Ca2+]i and insulin secretion were completely abolished by AG490 and JAK2 inhibitor II, the inhibitors had no effect on insulin secretion stimulated by a high K+ concentration. Similarly, Src kinase inhibitor-1 and PP2, but not its inactive analog PP3, suppressed [Ca2+]i elevation and completely abolished insulin secretion stimulated by hGH but did not affect responses to K+. Ovine prolactin increased [Ca2+]i and insulin secretion to a similar extent as hGH, effects prevented by the JAK2 and Src kinase inhibitors. In contrast, bovine GH evoked a rise in [Ca2+]i but did not stimulate insulin secretion. Neither JAK2 nor Src kinase inhibitors influenced the effect of bovine GH on [Ca2+]i. Our study indicates that hGH stimulates rise in [Ca2+]i and insulin secretion mainly through activation of the prolactin receptor and JAK2 and Src kinases in rat insulin-secreting cells. c-Src; growth hormone receptor; prolactin receptor; Ca2+-induced Ca2+ release 相似文献
16.
Evidence for Na+/Ca2+ exchange in intact single skeletal muscle fibers from the mouse 总被引:1,自引:0,他引:1
Balnave Christopher D.; Allen David G. 《American journal of physiology. Cell physiology》1998,274(4):C940
The myoplasmic free Ca2+concentration([Ca2+]i)was measured in intact single fibers from mouse skeletal muscle withthe fluorescent Ca2+ indicatorindo 1. Some fibers were perfused in a solution in which theconcentration of Na+ was reducedfrom 145.4 to 0.4 mM (low-Na+solution) in an attempt to activate reverse-modeNa+/Ca2+exchange (Ca2+ entry in exchangefor Na+ leaving the cell). Undernormal resting conditions, application oflow-Na+ solution only increased[Ca2+]iby 5.8 ± 1.8 nM from a mean resting[Ca2+]iof 42 nM. In other fibers,[Ca2+]iwas elevated by stimulating sarcoplasmic reticulum (SR)Ca2+ release with caffeine (10 mM)and by inhibiting SR Ca2+ uptakewith2,5-di(tert-butyl)-1,4-benzohydroquinone(TBQ; 0.5 µM) in an attempt to activate forward-modeNa+/Ca2+exchange (Ca2+ removal from thecell in exchange for Na+ influx).These two agents caused a large increase in[Ca2+]i,which then declined to a plateau level approximately twice the baseline[Ca2+]iover 20 min. If the cell was allowed to recover between exposures tocaffeine and TBQ in a solution in whichCa2+ had been removed, theincrease in[Ca2+]iduring the second exposure was very low, suggesting thatCa2+ had left the cell during theinitial exposure. Application of caffeine and TBQ to a preparation inlow-Na+ solution produced a large,sustained increase in[Ca2+]iof ~1 µM. However, when cells were exposed to caffeine and TBQ in alow-Na+ solution in whichCa2+ had been removed, a sustainedincrease in[Ca2+]iwas not observed, although[Ca2+]iremained higher and declined slower than in normalNa+ solution. This suggests thatforward-modeNa+/Ca2+exchange contributed to the fall of[Ca2+]iin normal Na+ solution, but whenextracellular Na+ was low, aprolonged elevation of[Ca2+]icould activate reverse-modeNa+/Ca2+exchange. The results provide evidence that skeletal muscle fibers possess aNa+/Ca2+exchange mechanism that becomes active in its forward mode when [Ca2+]iis increased to levels similar to that obtained during contraction. 相似文献
17.
Aromolaran AS Zima AV Blatter LA 《American journal of physiology. Cell physiology》2007,293(1):C106-C118
The role of glycolytically generated ATP in Ca2+/calmodulin-dependent kinase II (CaMKII)-mediated regulation of intracellular Ca2+ signaling was examined in cultured calf pulmonary artery endothelial (CPAE) cells. Exposure of cells (extracellular Ca2+ concentration = 2 mM) to glycolytic inhibitors 2-deoxy-D-glucose (2-DG), pyruvate (pyr) + -hydroxybutyrate (-HB), or iodoacetic acid (IAA) caused an increase of intracellular Ca2+ concentration ([Ca2+]i). CaMKII inhibitors (KN-93, W-7) triggered a similar increase of [Ca2+]i. The rise of [Ca2+]i was characterized by a transient spike followed by a small sustained plateau of elevated [Ca2+]i. In the absence of extracellular Ca2+ 2-DG caused an increase in [Ca2+]i, suggesting that inhibition of glycolysis directly triggered release of Ca2+ from intracellular endoplasmic reticulum (ER) Ca2+ stores. The inositol-1,4,5-trisphosphate receptor (IP3R) inhibitor 2-aminoethoxydiphenyl borate abolished the KN-93- and 2-DG-induced Ca2+ response. Ca2+ release was initiated in peripheral cytoplasmic processes from which activation propagated as a [Ca2+]i wave toward the central region of the cell. Focal application of 2-DG resulted in spatially confined elevations of [Ca2+]i. Propagating [Ca2+]i waves were preceded by [Ca2+]i oscillations and small, highly localized elevations of [Ca2+]i (Ca2+ puffs). Inhibition of glycolysis with 2-DG reduced the KN-93-induced Ca2+ response, and vice versa during inhibition of CaMKII 2-DG-induced Ca2+ release was attenuated. Similar results were obtained with pyr + -HB and W-7. Furthermore, 2-DG and IAA caused a rapid increase of intracellular Mg2+ concentration, indicating a concomitant drop of cellular ATP levels. In conclusion, CaMKII exerts a profound inhibition of ER Ca2+ release in CPAE cells, which is mediated by glycolytically generated ATP, possibly through ATP-dependent phosphorylation of the IP3R. Ca2+/calmodulin-dependent kinase II; glycolysis; calcium regulation 相似文献
18.
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
19.
We testedthe hypothesis that strain is the primary mechanical signal in themechanosensitive modulation of intracellular Ca2+concentration ([Ca2+]i) in airway smoothmuscle. We found that [Ca2+]i wassignificantly correlated with muscle length during isotonic shorteningagainst 20% isometric force (Fiso). When the isotonic loadwas changed to 50% Fiso, data points from the 20 and 50% Fiso experiments overlapped in thelength-[Ca2+]i relationship. Similarly, datapoints from the 80% Fiso experiments clustered near thosefrom the 50% Fiso experiments. Therefore, despite 2.5- and4-fold differences in external load, [Ca2+]idid not deviate much from the length-[Ca2+]irelation that fitted the 20% Fiso data. Maximal inhibition of sarcoplasmic reticular (SR) Ca2+ uptake by 10 µMcyclopiazonic acid (CPA) did not significantly change[Ca2+]i in carbachol-induced isometriccontractions and isotonic shortening. CPA also did not significantlychange myosin light-chain phosphorylation or force redevelopment whencarbachol-activated muscle strips were quickly released from optimallength (Lo) to 0.5 Lo. These results are consistent with thehypothesis and suggest that SR Ca2+ uptake is not theunderlying mechanism. 相似文献
20.
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