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1.
JIAN Ling-Cheng SUN Long-Hua LI Ji-Hong WANG Hong SUN De-Lan Paul H LI 《植物学报(英文版)》2000,42(8):803-810
A comparative study was carried out on the EM-cytochemical localization of calcium and Ca2+-ATPase activity in the suspension-cultured cells between the chilling-sensitive maize (Zea mays L. cv. Black Mexican Sweet) and chilling-insensitive Trititrigia (Triticum sect. Trititrigia mackey) at 4 ℃ chilling. When maize and Tyititrigia cells were cultured at 26 ℃, electron microscopic observations revealed that the electron-dense calcium antimonate deposits, an indication of the calcium localization, were localized mainly in the vacuoles, and few was found in the cytosol and nuclei. The electron-dense cerium phosphate deposits, an indication of Ca2+-ATPase activity, were abundantly distributed on the plasma membrane (PM). When the cells from both species were cultured at 4 ℃ for 1 and 3 h, an elevation of Ca2+ level in the cytosol and nuclei was observed, whereas the cerium phosphate deposits on the PM showed no quantitative difference from those of the 26 ℃-cultured cells, indicating that the enzymatic activities were not altered during these chilling periods. However, there was a distinct difference in the dynamics of the Ca2+ distribution and the PM Ca2+-ATPase activity between maize and Trititrigia when chilled at 4 ℃ for 12, 24 and 72 h. In maize cells, a large number of Ca2+ deposits still existed in the cytosol and nuclei, and the PM Ca2+-ATPase became less and less active, and even inactive at all. In Trititrigia cells, the increased cytosolic and nuclear Ca2+ ions decreased after 12 h chilling. By chilling up to 24 and 72 h, the intracellular Ca2+ concentration had been restored to a similar low level as those of the warm temperature-cultured cells, while the activity of the PM Ca2+-ATPase maintained high. The transient cytosolic and nuclear Ca2+ increase and the activities of PM Ca2+-ATPase during chilling are discussed in relation to plant cold hardiness. 相似文献
2.
NaHCO3胁迫下星星草根中Ca2+与Ca2+-ATPase 的超微细胞化学定位 总被引:2,自引:1,他引:2
利用焦锑酸盐和磷酸铅沉淀技术分别对NaHCO3胁迫条件下星星草(Puccinellia tenuiflora)根中Ca2+和Ca2+-ATPase 进行超微细胞化学定位研究, 旨在进一步探讨Ca2+在NaHCO3胁迫诱导胞内信号转导过程中的作用, 以及Ca2+-ATPase活性定位变化与NaHCO3胁迫下星星草抗盐碱能力的关系。结果表明: 在正常状态下, 根毛区细胞质内Ca2+较少, 主要位于质膜附近和液泡中, Ca2+-ATPase主要定位于质膜和液泡膜, 有一定活性。在0.448%NaHCO3胁迫下, 根毛区细胞质中Ca2+增多, 液泡中Ca2+减少, 且主要集中于液泡膜附近, 质膜和液泡膜Ca2+-ATPase活性明显升高。在1.054%NaHCO3胁迫下,细胞质中分布的Ca2+增多, 而液泡中Ca2+极少, Ca2+-ATPase活性也降低。以上结果表明, Ca2+亚细胞定位和Ca2+-ATPase活性变化在星星草响应NaHCO3胁迫的信号传递过程中具有重要作用。 相似文献
3.
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
4.
Alterations in ultrastructure and subcellular localization of Ca2+ in poplar apical bud cells during the induction of dormancy 总被引:2,自引:0,他引:2
Jian Ling-cheng; Li Paul H.; Sun Long-hua; Chen Tony H.H. 《Journal of experimental botany》1997,48(6):1195-1207
In poplar (Populus deltoides Bartr. ex Marsh), bud dormancyand freezing tolerance were concomitantly induced by short-day(SD) photoperiods. Ultrastructural changes and the alterationin subcellular localization of calcium in apical bud cells associatedwith dormancy development were investigated. During the developmentof dormancy, the thickness of cell walls increased significantly,the number of starch granules increased, and there was a significantaccumulation of storage proteins in the vacuoles of the apicalbud cells. The most striking change was the constriction andblockage of the plasmodesmata. It was demonstrated that antimonate precipitation is a reliabletechnique for studying subcellular localization of calcium inpoplar apical bud cells. Under the long day (LD) photoperiod,electron-dense calcium antimonate precipitates were mainly localizedin vacuoles, intercellular spaces and plastids. Some antimonateprecipitates were also found in the cell walls and at the entranceof the plasmodesmata. However, there were few Ca2+ depositsfound in the cytosol and nucleus. After 20 d of SD exposure,when development of bud dormancy was initiated, calcium depositsin intercellular spaces were decreased, whereas some depositswere found in the cytosol and nuclei. From 2849 d ofSD exposure, while dormancy was developing, a large number ofCa2+ precipitates were found in the cytosol and nuclei. Whendeep dormancy was reached after 77 d of SD exposure, Ca2+ depositsbecame fewer in both cytosol and nuclei, whereas numerous depositswere again observed in the cell walls and in the intercellularspaces. These results suggest that under the influence of SDphotoperiods, there are alterations in subcellular Ca2+ localization,and changes in ultrastructure of apical bud cells during thedevelopment of dormancy. The constriction and blockage of plasmodesmatamay cause the cessation of symplastic transport, limit cellularcommunication and signal transduction between adjacent cells,which in turn may lead to events associated with growth cessationand dormancy development in buds. Key words: Poplar, apical bud cells, Ca2+ subcellular localization, dormancy 相似文献
5.
Takeda Yuichi; Ogawa Tomoko; Nakamura Yoshiyuki; Kasamo Kunihiro; Sakata Makoto; Ohta Eiji 《Plant & cell physiology》1995,36(5):865-871
Intracellular pH and levels of ATP in intact root-tip cellsof mung bean (Vigna mungo [L.] Hepper) under low-temperaturestress were investigated in vivo by 31P nuclear magnetic resonance(31P-NMR) spectroscopy. Root-tips of 3 mm in length were excisedfrom seedlings of mung bean that had been chilled at 0°Cafter grown at 30°C. Chilling for longer than 12 h causedchanges in the intracellular pH and decreased levels of ATPin the seedlings. The level of ATP recovered within 30 min butlittle change in pH was observed when samples were rewarmedto 20° C after chilling at 5°C. However, after chillingfor longer than 48 h, neither the intracellular pH nor the levelof ATP was restored. These results suggest that a decline in the activity of tonoplastH+-ATPase, induced by chillings, might be a significant earlyevent in cold-induced injury that leads to cell damage. (Received October 27, 1994; Accepted May 10, 1995) 相似文献
6.
SYNOPSIS. Actomyosin was extracted from skeletal muscle of Coryphaenoides,a benthic fish living at 2,200 meters depth, at a temperatureof 2°C, or less, and at pressure of 3,000 psi. On SDS-ureaelectrophoresis on acrylamide gel, the actomyosin extracts yieldcomponents of apparent molecular weight 210,000 (myosin heavychains), 47,000 (actin), 35,000 (tropomyosin and/or troponinsubunits), and 13,000 (myosin light chains). The Mg2+-ATPaseof Coryphaenoides actomyosin shows a complex Arrhenius plot,with marked denaturation at temperatures above 30°C, anddiminished temperature sensitivity at temperatures below 15°C.Mg2+-ATPase is inhibited by pressure, with activation volumesof + 160 cc/mole at 25°C, and + 230 cc/mole at 2°C.Ca2+-ATPase of actomyosin exhibits the same pH, temperature,and pressure dependence as Ca2+-ATPase of myosin. The overalldata would be consistent with a positive activation volume thatis independent of temperature (to first approximation) and isrelated to the interaction of actin and myosin, and a negativeactivation volume that is temperature dependent and is relateddirectly to activation of myosin ATPase. The net effect appearsto be an adaptive mechanism whereby Mg2+-ATPase of Coryphaenoidesactomyosin is relatively insensitive to pressure and temperatureunder conditions encountered by the living fish. 相似文献
7.
Effects of elevated physiological temperatures on sarcoplasmic reticulum function in mechanically skinned muscle fibers of the rat 总被引:2,自引:0,他引:2
Properties of the sarcoplasmic reticulum (SR) with respect to Ca2+ loading and release were measured in mechanically skinned fiber preparations from isolated extensor digitorum longus (EDL) muscles of the rat that were either kept at room temperature (23°C) or exposed to temperatures in the upper physiological range for mammalian skeletal muscle (30 min at 40 or 43°C). The ability of the SR to accumulate Ca2+ was significantly reduced by a factor of 1.92.1 after the temperature treatments due to a marked increase in SR Ca2+ leak, which persisted for at least 3 h after treatment. Results with blockers of Ca2+ release channels (ruthenium red) and SR Ca2+ pumps [2,5-di(tert-butyl)-1,4-hydroquinone] indicate that the increased Ca2+ leak was not through the SR Ca2+ release channel or the SR Ca2+ pump, although it is possible that the leak pathway was via oligomerized Ca2+ pump molecules. No significant change in the maximum SR Ca2+-ATPase activity was observed after the temperature treatment, although there was a tendency for a decrease in the SR Ca2+-ATPase. The observed changes in SR properties were fully prevented by the superoxide (O2) scavenger Tiron (20 mM), indicating that the production of O2 at elevated temperatures is responsible for the increase in SR Ca2+ leak. Results show that physiologically relevant elevated temperatures 1) induce lasting changes in SR properties with respect to Ca2+ handling that contribute to a marked increase in the SR Ca2+ leak and, consequently, to the reduction in the average coupling ratio between Ca2+ transport and SR Ca2+-ATPase and muscle performance, and 2) that these changes are mediated by temperature-induced O2 production. skeletal muscle; calcium ion leak; superoxide; skinned fibers 相似文献
8.
Cucumber (Cucumis sativus L.) seedlings were grafted onto cucumber-(CG) or figleaf gourd- (FG, Cucurbita ficifolia Bouché)seedlings in order to determine the effect of solution temperature(12, 22, and 32°C) on the mineral composition of xylem sapand the plasma membrane K+-Mg++-ATPase activities of the roots.Low solution temperature (12°C) lowered the concentrationof NO3 and H2PO4 in xylem sap of CG plants butnot of FG plants. Concentrations of K+, Ca++ and Mg++ in xylemsap were less affected than anions by solution temperature.The plasma membrane of FG plants grown in 12°C solutiontemperature showed the highest K+- Mg++-ATPase activity at allATP concentrations up to 3 mM and at low reaction temperatureup to 12°C, indicating resistance of figleaf gourd to lowroot temperature. (Received December 27, 1994; Accepted March 10, 1995) 相似文献
9.
Ryyppo A.; Vapaavuori E.M.; Rikala R.; Sutinen M.-L. 《Journal of experimental botany》1994,45(11):1533-1539
The fatty acid composition of phospholipids in the microsomesand the vanadate-sensitive H+-ATPase activity of the roots ofone-year-old Scots pine (Pinus sylvestris L.) seedlings werestudied during flushing in spring. The seedlings in hydroponiccultures were subjected to different root temperatures (5, 12or 20°C). The shoot was maintained at 20/15° C (day/night)during the 35 d experiment. After 35 d at 5° C, root growthwas totally inhibited and shoot growth partly inhibited. In roots grown at 5° C the fatty acid composition of themicrosomal phospholipids and the degree of fatty acid unsaturation(bond index) were unchanged, while in roots grown at 12 and20° C the fatty acid composition changed and bond indexdecreased. At those root temperatures, the most obvious changewas a decline in the proportion of linolenic acid (C18:3). Inthe new white roots grown either at 12°C or 20°C theproportion of C18:2 was higher and the proportion of C18:3 lowerthan in 1-year-old roots. Independently of root temperature,H+-ATPase activity, determined on a fresh weight basis, declinedto half of the original activity during the experiment. Thedecline in H+ -ATPase activity was most rapid during the firstweek. In the old roots the decline in H+-ATPase activity followedclosely the decline in amount of membrane protein. In new rootsH+-ATPase activity was high and increased with increasing roottemperature. These results suggest that in the roots of Scotspine seedlings, vanadate-sensitive H+-ATPase activity is dependenton age, while changes in the microsomal fatty acid compositionof phospholipids are regulated mainly by root temperature. Key words: Fatty acids of phospholipids, microsomes, H+-ATPase, root temperature, Scots pine 相似文献
10.
Phototropins (phot1 and phot2) are blue light (BL) receptorsthat mediate responses including phototropism, chloroplast movementand stomatal opening, and increased cytosolic Ca2+. BL absorbedby phototropins activates plasma membrane H+-ATPase in guardcells, resulting in membrane hyperpolarization, and drives K+uptake and stomatal opening. However, it is unclear whetherthe phototropin-mediated Ca2+ increase activates the H+-ATPase.Here, we determined cytosolic Ca2+ concentrations in guard cellprotoplasts (GCPs) from Arabidopsis transformed with aequorin.Cytosolic Ca2+ increased rapidly in response to BL in GCPs fromboth the wild type and phot1 phot2 double mutants, but was mostlysuppressed by an inhibitor of photosynthetic electron flow (DCMU).With depleted external K+, we observed another slower Ca2+ increase,which was phototropin- dependent. Fusicoccin, a H+-ATPase activator,mimicked the effect of BL. The slow Ca2+ increase thus appearsto result from membrane hyperpolarization. The slow Ca2+ increasewas suppressed by external K+ and was restored by blockers ofinward-rectifying K+ channels, CsCl and tetraethylammonium,suggesting the preferential uptake of K+ over Ca2+. Such efficientK+ uptake in response to BL was not found in mesophyll cells.Both the fast and the slow Ca2+ increases were inhibited byCa2+ channel blockers (CoCl2 and LaCl3) and a chelating agent(EGTA). These results indicate that the phototropin-mediatedCa2+ increase was not observed prior to H+-ATPase activationin guard cells and that Ca2+ entered guard cells via Ca2+ channelsthrough photosynthesis and phototropin-mediated membrane hyperpolarization. 相似文献
11.
Ortega A Becker VM Alvarez R Lepock JR Gonzalez-Serratos H 《American journal of physiology. Cell physiology》2000,279(1):C166-C172
Experiments were performedto determine whether the organic Ca2+ channel blocker D-600(gallopamil), which penetrates into muscle cells, affects sarcoplasmicreticulum (SR) Ca2+ uptake by directly inhibiting the lightSR Ca2+-ATPase. We have previously shown that at 10 µM,D-600 inhibits LSR ATP-dependent Ca2+ uptake by 50% buthas no effect on ATPase activity (21). These data suggestthat the SR Ca2+-ATPase might be a potential target forD-600. The ATPase activity of the enzyme is associated with itshydrophilic cytoplasmic domain, whereas Ca2+ binding andtranslocation are associated with the transmembrane domain(18). In the present experiments, we determined which of the two domains of the ATPase is affected by D-600. Thermalinactivation experiments using the SR Ca2+-ATPasedemonstrated that D-600 decreased the thermal stability ofCa2+ transport but had no effect on the stability of ATPaseactivity. In addition, D-600 at a concentration of 160 µM did nothave any leaking effect of Ca2+ on theCa2+-loaded SR. Thermal denaturation profiles of SRmembranes revealed that D-600 interacts directly with the transmembranedomain of the Ca2+-ATPase. No evidence for interaction withthe nucleotide domain was obtained. We conclude that theCa2+ blocker D-600 inhibits the SR Ca2+ pumpspecifically by interacting with the transmembraneCa2+-binding domain of the Ca2+-ATPase. 相似文献
12.
Caloxin: a novel plasma membrane Ca2+ pump inhibitor 总被引:1,自引:0,他引:1
Chaudhary J Walia M Matharu J Escher E Grover AK 《American journal of physiology. Cell physiology》2001,280(4):C1027-C1030
Plasma membrane (PM) Ca2+ pump is aCa2+-Mg2+-ATPase that expels Ca2+from cells to help them maintain low concentrations of cytosolic Ca2+. There are no known extracellularly acting PMCa2+ pump inhibitors, as digoxin and ouabain are forNa+ pump. In analogy with digoxin, we define caloxins asextracellular PM Ca2+ pump inhibitors and describe caloxin2A1. Caloxin 2A1 is a peptide obtained by screening a random peptidephage display library for binding to the second extracellular domain(residues 401-413) sequence of PM Ca2+ pump isoform1b. Caloxin 2A1 inhibits Ca2+-Mg2+-ATPase inhuman erythrocyte leaky ghosts, but it does not affect basalMg2+-ATPase or Na+-K+-ATPase in theghosts or Ca2+-Mg2+-ATPase in the skeletalmuscle sarcoplasmic reticulum. Caloxin 2A1 also inhibitsCa2+-dependent formation of the 140-kDa acid-stableacylphosphate, which is a partial reaction of this enzyme. Consistentwith inhibition of the PM Ca2+ pump in vascularendothelium, caloxin 2A1 produces an endothelium-dependent relaxationthat is reversed byNG-nitro-L-arginine methyl ester.Thus caloxin 2A1 is a novel PM Ca2+ pump inhibitor selectedfor binding to an extracellular domain. 相似文献
13.
Synaptotagmin I increases the probability of vesicle fusion at low [Ca2+] in pituitary cells 总被引:1,自引:0,他引:1
Kreft M Kuster V Grilc S Rupnik M Milisav I Zorec R 《American journal of physiology. Cell physiology》2003,284(2):C547-C554
Synaptotagmin I (Syt I),a low-affinity Ca2+-binding protein, is thought to serve asthe Ca2+ sensor in the release of neurotransmitter.However, functional studies on the calyx of Held synapse revealed thatthe rapid release of neurotransmitter requires only approximatelymicromolar [Ca2+], suggesting that Syt I may play a morecomplex role in determining the high-affinity Ca2+dependence of exocytosis. Here we tested this hypothesis by studying pituitary cells, which possess high- and low-affinityCa2+-dependent exocytic pathways and express Syt I. Usingpatch-clamp capacitance measurements to monitor secretion and the acuteantisense deletion of Syt I from differentiated cells, we have shownthat the rapid and the most Ca2+-sensitive pathway ofexocytosis in rat melanotrophs requires Syt I. Furthermore, stimulationof the Ca2+-dependent exocytosis by cytosol dialysis withsolutions containing 1 µM [Ca2+] was completelyabolished in the absence of Syt I. Similar results were obtained by thepreinjection of antibodies against the CAPS (Ca2+-dependentactivator protein for secretion) protein. These results indicate thatsynaptotagmin I and CAPS proteins increase the probability of vesiclefusion at low cytosolic [Ca2+]. 相似文献
14.
The antimonate-staining procedure and X-ray microanalysis techniquewere used to determine the pattern of Ca2+ localization in etiolatedoat (Avena sativa L.) coleoptile parenchyma cells. Precipitatesof calcium antimonate, indicating the presence of Ca2+ and confirmedby X-ray microanalysis, were found associated with the outerand inner surfaces of the plasma membrane of cells of dark-grownseedlings. After exposure of seedlings to red light, precipitatesof calcium antimonate were additionally observed in cisternaeof the endoplasmic reticulum. In the cells of oat coleoptilesexposed to red light and then followed immediately by farredlight, Ca2+ was observed on the outside of the plasma membrane,in cell walls and in the vacuoles. The results suggest thatphytochrome mediates the regulation of the intracellular Ca2+localization. Key words: Antimonate procedure, Avena sativa L., Ca2+ (localization), phytochrome, X-ray microanalysis 相似文献
15.
Pancreatitis is an inflammatory disease of pancreatic acinar cells whereby intracellular calcium concentration ([Ca2+]i) signaling and enzyme secretion are impaired. Increased oxidative stress has been suggested to mediate the associated cell injury. The present study tested the effects of the oxidant, hydrogen peroxide, on [Ca2+]i signaling in rat pancreatic acinar cells by simultaneously imaging fura-2, to measure [Ca2+]i, and dichlorofluorescein, to measure oxidative stress. Millimolar concentrations of hydrogen peroxide increased cellular oxidative stress and irreversibly increased [Ca2+]i, which was sensitive to antioxidants and removal of external Ca2+, and ultimately led to cell lysis. Responses were also abolished by pretreatment with (sarco)endoplasmic reticulum Ca2+-ATPase inhibitors, unless cells were prestimulated with cholecystokinin to promote mitochondrial Ca2+ uptake. This suggests that hydrogen peroxide promotes Ca2+ release from the endoplasmic reticulum and the mitochondria and that it promotes Ca2+ influx. Lower concentrations of hydrogen peroxide (10–100 µM) increased [Ca2+]i and altered cholecystokinin-evoked [Ca2+]i oscillations with marked heterogeneity, the severity of which was directly related to oxidative stress, suggesting differences in cellular antioxidant capacity. These changes in [Ca2+]i also upregulated the activity of the plasma membrane Ca2+-ATPase in a Ca2+-dependent manner, whereas higher concentrations (0.1–1 mM) inactivated the plasma membrane Ca2+-ATPase. This may be important in facilitating "Ca2+ overload," resulting in cell injury associated with pancreatitis. oxidant stress; pancreatitis; calcium pump 相似文献
16.
The effects of Na-orthovanadate, at concentrations only partiallyinhibiting net H+ extrusion, were determined on vacuolar andcytosolic pH by the weak base and weak acid distribution atequilibrium. Treatment with vanadate induces in Elodea densaleaves and in Arabidopsis thaliana seedlings a moderate acidificationof both cell sap and vacuole. Conversely, it induces an alkalinizationof cytosol, this effect being in apparent contrast with a conditionof reduced activity of the H+-transporting plasmalemma ATPase,which should be associated with a cytosolic acidification. InArabidopsis seedlings treated with vanadate, the increase inpH of both cytosol and external medium is associated with adecrease in cell sap buffer capacity, more evident for highervanadate concentrations, and particularly marked in the pH rangebetween 3·5 and 5·5. In these conditions, themalate content is strongly reduced, its decrease almost completelyaccounting for the decrease in cell sap buffer capacity. Anin vitro analysis of the vanadate effect on phosphoenolpyruvatecarboxylase indicates that the decrease in malate content seemssubstantially due to an inhibiting effect of vanadate on thisenzyme. These results stress that the in vivo use of vanadateas an inhibitor of the plasmalemma H+-ATPase must be taken withcaution; in particular, for studying the correlations betweenchanges in net H+ extrusion and changes in cytosolic pH andrelated processes. Key words: Vanadate, malate, cytosolic pH, Elodea densa, Arabidopsis thaliana 相似文献
17.
Coordinate downregulation of CaM kinase II and phospholamban accompanies contractile phenotype transition in the hyperthyroid rabbit soleus 总被引:1,自引:0,他引:1
Jiang M Xu A Jones DL Narayanan N 《American journal of physiology. Cell physiology》2004,287(3):C622-C632
This study investigated the effects of L-thyroxine-induced hyperthyroidism on Ca2+/calmodulin (CaM)-dependent protein kinase (CaM kinase II)-mediated sarcoplasmic reticulum (SR) protein phosphorylation, SR Ca2+ pump (Ca2+-ATPase) activity, and contraction duration in slow-twitch soleus muscle of the rabbit. Phosphorylation of Ca2+-ATPase and phospholamban (PLN) by endogenous CaM kinase II was found to be significantly lower (3050%) in soleus of the hyperthyroid compared with euthyroid rabbit. Western blotting analysis revealed higher levels of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) 1 (150%) Ca2+ pump isoform, unaltered levels of SERCA2 Ca2+ pump isoform, and lower levels of PLN (50%) and -, -, and -CaM kinase II (40 70%) in soleus of the hyperthyroid rabbit. SR vesicles from hyperthyroid rabbit soleus displayed approximately twofold higher ATP-energized Ca2+ uptake and Ca2+-stimulated ATPase activities compared with that from euthyroid control. The Vmax of Ca2+ uptake (in nmol Ca2+·mg SR protein1·min1: euthyroid, 818 ± 73; hyperthyroid, 1,649 ± 90) but not the apparent affinity of the Ca2+-ATPase for Ca2+ (euthyroid, 0.97 ± 0.02 µM, hyperthyroid, 1.09 ± 0.04 µM) differed significantly between the two groups. CaM kinase II-mediated stimulation of Ca2+ uptake by soleus muscle SR was 60% lower in the hyperthyroid compared with euthyroid. Isometric twitch force of soleus measured in situ was significantly greater (36%), and the time to peak force and relaxation time were significantly lower (3040%), in the hyperthyroid. These results demonstrate that thyroid hormone-induced transition in contractile properties of the rabbit soleus is associated with coordinate downregulation of the expression and function of PLN and CaM kinase II and selective upregulation of the expression and function of SERCA1, but not SERCA2, isoform of the SR Ca2+ pump. calmodulin kinase II; phospholamban ; calcium ion-adenosinetriphosphatase; sarcoplasmic reticulum 相似文献
18.
Palmer Bradley M.; Lynch Joshua M.; Snyder Steven M.; Moore Russell L. 《Journal of applied physiology》1999,86(2):584-591
The effects ofendurance run training onNa+-dependentCa2+ regulation in rat leftventricular myocytes were examined. Myocytes were isolated fromsedentary and trained rats and loaded with fura 2. Contractile dynamicsand fluorescence ratio transients were recorded during electricalpacing at 0.5 Hz, 2 mM extracellular Ca2+ concentration, and 29°C.Resting and peak cytosolic Ca2+concentration([Ca2+]c)did not change with exercise training. However, resting and peak[Ca2+]cincreased significantly in both groups during 5 min of continuous pacing, although diastolic[Ca2+]cin the trained group was less susceptible to this elevation ofintracellular Ca2+. Run trainingalso significantly reduced the rate of[Ca2+]cdecay during relaxation. Myocytes were then exposed to 10 mM caffeinein the absence of external Na+ orCa2+ to trigger sarcoplasmicreticular Ca2+ release and tosuppress cellular Ca2+ efflux.This maneuver elicited an elevated steady-state[Ca2+]c.External Na+ was then added, andthe rate of[Ca2+]cclearance was determined. Run training significantly reduced the rateof Na+-dependent clearance of[Ca2+]cduring the caffeine-induced contractures. These data demonstrate thatthe removal of cytosolic Ca2+ wasdepressed with exercise training under these experimental conditionsand may be specifically reflective of a training-induced decrease inthe rate of cytosolic Ca2+ removalviaNa+/Ca2+exchange and/or in the amount ofCa2+ moved across the sarcolemmaduring a contraction. 相似文献
19.
Integration of rapid cytosolic Ca2+ signals by mitochondria in cat ventricular myocytes 总被引:2,自引:0,他引:2
Sedova M Dedkova EN Blatter LA 《American journal of physiology. Cell physiology》2006,291(5):C840-C850
Decoding of fast cytosolic Ca2+ concentration ([Ca2+]i) transients by mitochondria was studied in permeabilized cat ventricular myocytes. Mitochondrial [Ca2+] ([Ca2+]m) was measured with fluo-3 trapped inside mitochondria after removal of cytosolic indicator by plasma membrane permeabilization with digitonin. Elevation of extramitochondrial [Ca2+] ([Ca2+]em) to >0.5 µM resulted in a [Ca2+]em-dependent increase in the rate of mitochondrial Ca2+ accumulation ([Ca2+]em resulting in half-maximal rate of Ca2+ accumulation = 4.4 µM) via Ca2+ uniporter. Ca2+ uptake was sensitive to the Ca2+ uniporter blocker ruthenium red and the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone and depended on inorganic phosphate concentration. The rates of [Ca2+]m increase and recovery were dependent on the extramitochondrial [Na+] ([Na+]em) due to Ca2+ extrusion via mitochondrial Na+/Ca2+ exchanger. The maximal rate of Ca2+ extrusion was observed with [Na+]em in the range of 2040 mM. Rapid switching (0.251 Hz) of [Ca2+]em between 0 and 100 µM simulated rapid beat-to-beat changes in [Ca2+]i (with [Ca2+]i transient duration of 100500 ms). No [Ca2+]m oscillations were observed, either under conditions of maximal rate of Ca2+ uptake (100 µM [Ca2+]em, 0 [Na+]em) or with maximal rate of Ca2+ removal (0 [Ca2+]em, 40 mM [Na+]em). The slow frequency-dependent increase of [Ca2+]m argues against a rapid transmission of Ca2+ signals between cytosol and mitochondria on a beat-to-beat basis in the heart. [Ca2+]m changes elicited by continuous or pulsatile exposure to elevated [Ca2+]em showed no difference in mitochondrial Ca2+ uptake. Thus in cardiac myocytes fast [Ca2+]i transients are integrated by mitochondrial Ca2+ transport systems, resulting in a frequency-dependent net mitochondrial Ca2+ accumulation. mitochondrial Ca2+; excitation-contraction coupling; cardiomyocytes 相似文献
20.
Aortic smooth muscle and endothelial plasma membrane Ca2+ pump isoforms are inhibited differently by the extracellular inhibitor caloxin 1b1 总被引:1,自引:0,他引:1
Pande J Mallhi KK Sawh A Szewczyk MM Simpson F Grover AK 《American journal of physiology. Cell physiology》2006,290(5):C1341-C1349
Plasma membrane Ca2+ pumps (PMCA) that expel Ca2+ from cells are encoded by four genes (PMCA14). In this study, we show that aortic endothelium and smooth muscle differ in their PMCA isoform mRNA expression: endothelium expressed predominantly PMCA1, and smooth muscle expressed PMCA4 and a lower level of PMCA1. In this study, we report a novel peptide (caloxin 1b1, obtained by screening for binding to extracellular domain 1 of PMCA4), which inhibited PMCA extracellularly, selectively, and had a higher affinity for PMCA4 than PMCA1. It inhibited the PMCA Ca2+-Mg2+-ATPase activity in leaky erythrocyte ghosts (mainly PMCA4) with a Ki value of 46 ± 5 µM, making it 10x more potent than the previously reported caloxin 2a1. It was isoform selective because it inhibited the PMCA1 Ca2+-Mg2+-ATPase in human embryonic kidney-293 cells with a higher Ki value (105 ± 11 µM) than for PMCA4. Caloxin 1b1 was selective in that it did not inhibit other ATPases. Because caloxin 1b1 had been selected to bind to an extracellular domain of PMCA, it could be added directly to cells and tissues to examine its effects on smooth muscle and endothelium. In deendothelialized aortic rings, caloxin 1b1 (200 µM) produced a contraction. It also increased the force of contraction produced by a submaximum concentration of phenylephrine. In aortic rings with endothelium intact, precontracted with phenylephrine and relaxed partially with a submaximum concentration of carbachol, caloxin 1b1 increased the force of contraction rather than potentiating the endothelium-dependent relaxation. In cultured cells, caloxin 1b1 increased the cytosolic [Ca2+] more in arterial smooth muscle cells than in endothelial cells. Thus caloxin 1b1 is the first highly selective extracellular PMCA inhibitor that works better on vascular smooth muscle than on endothelium. coronary artery; rat aorta; smooth muscle; endothelium 相似文献