共查询到20条相似文献,搜索用时 31 毫秒
1.
Inuyama M Ushigome F Emoto A Koyabu N Satoh S Tsukimori K Nakano H Ohtani H Sawada Y 《American journal of physiology. Cell physiology》2002,283(3):C822-C830
Thecharacteristics of L-lactic acid transport across thetrophoblast basal membrane were investigated and compared with those across the brush-border membrane by using membrane vesicles isolated from human placenta. The uptake ofL-[14C]lactic acid into basal membranevesicles was Na+ independent, and an uphill transport wasobserved in the presence of a pH gradient([H+]out > [H+]in).L-[14C]lactic acid uptake exhibitedsaturation kinetics with a Km value of 5.89 ± 0.68 mM in the presence of a pH gradient.p-Chloromercuribenzenesulfonate and-cyano-4-hydroxycinnamate inhibited the initial uptake, whereas phloretin or 4,4'-diisothiocyanostilbene-2,2'-disulfonate did not.Mono- and dicarboxylic acids suppressed the initial uptake. Inconclusion, L-lactic acid transport in the basal membraneis H+ dependent and Na+ independent, as is alsothe case for the brush-border membrane transport, and itscharacteristics resemble those of monocarboxylic acid transporters.However, there were several differences in the effects of inhibitorsbetween basal and brush-border membrane vesicles, suggesting that thetransporter(s) involved in L-lactic acid transport in thebasal membrane of placental trophoblast may differ from those in thebrush-border membrane. 相似文献
2.
Ito M Haito S Furumoto M Uehata Y Sakurai A Segawa H Tatsumi S Kuwahata M Miyamoto K 《American journal of physiology. Cell physiology》2007,292(1):C526-C534
During bone resorption, a large amount of inorganic phosphate (Pi) is generated within the osteoclast hemivacuole. The mechanisms involved in the disposal of this Pi are not clear. In the present study, we investigated the efflux of Pi from osteoclast-like cells. Pi efflux was activated by acidic conditions in osteoclast-like cells derived by the treatment of RAW264.7 cells with receptor activator of nuclear factor-B ligand. Acid-induced Pi influx was not observed in renal proximal tubule-like opossum kidney cells, osteoblast-like MC3T3-E1 cells, or untreated RAW264.7 cells. Furthermore, Pi efflux was stimulated by extracellular Pi and several Pi analogs [phosphonoformic acid (PFA), phosphonoacetic acid, arsenate, and pyrophosphate]. Pi efflux was time dependent, with 50% released into the medium after 10 min. The efflux of Pi was increased by various inhibitors that block Pi uptake, and extracellular Pi did not affect the transport of [14C]PFA into the osteoclast-like cells. Preloading of cells with Pi did not stimulate Pi efflux by PFA, indicating that the effect of Pi was not due to transstimulation of Pi transport. Pi uptake was also enhanced under acidic conditions. Agents that prevent increases in cytosolic free Ca2+ concentration, including acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, 2-aminoethoxydiphenyl borate, and bongkrekic acid, significantly inhibited Pi uptake in the osteoclast-like cells, suggesting that Pi uptake is regulated by Ca2+ signaling in the endoplasmic reticulum and mitochondria of osteoclast-like cells. These results suggest that osteoclast-like cells have a unique Pi uptake/efflux system and can prevent Pi accumulation within osteoclast hemivacuoles. phosphate transporter; RAW264.7; proton dependent; acidification 相似文献
3.
To study possible changes in the transport metabolites betweenchloroplasts and cytoplasm during CAM induction of Mesembryanthemumcrystallinum, we compared substrate specificity of P11 translocator(s)in isolated chloroplasts from the C3 and CAM-induced plants.The [14C]glu-cose 6-phosphate (G6P) transport activity was significantonly in the chloroplasts of CAM-mode plants and not detectablein those of C3-mode, while a similar high rate of [32P]Pi uptakewas observed with both types of chloroplasts. Kinetic analysisof G6P uptake in the CAM chloroplasts showed a high Vmax [10.6µmol (mg Chl)1 h1] and a comparatively lowKm value (0.41 mM); the latter was similar to Ki values of Pi,3-phosphoglycerate and phospho-enolpyruvate, 0.30, 0.34 and0.47 mM, respectively. On the other hand, [32P]Pi uptake inthe CAM chloroplasts was inhibited competitively by G6P witha Ki value (8.4 mM) 20-fold higher than the Km value for G6Puptake, while that in C3 chloroplasts was not inhibited at all.These results suggest that a new G6P/Pi, counterexchange mechanismis induced in the chloroplast envelope of CAM-induced M. crystallinumin addition to the ordinary type of P, translocator, that cannottransport G6P, already present in the C3-type chloroplasts. (Received March 17, 1997; Accepted May 10, 1997) 相似文献
4.
Under conditions of apoplastic unloading from the sieve element-companioncell (se-cc) complexes in fully-elongated stems of Phaseolusvulgaris plants, gjbberellic acid (GA3 stimulated in vitro uptakeof [14C]sucrose by the stem tissues. The GA3, response dependedupon the incubate containing calcium ions and being bufferedat pH 6. The GA3 action could be accounted for by a reductionin the Michaelis-Menten constant of the uptake process. Promotedtransport by GA3 in the decapitated stems resulted in all thetissues accumulating higher levels of [14C]photosynthates. Comparisonof this response with that for in vitro uptake of [14C]sucroseindicated that GA3 stimulation of the sucrose uptake processcontributed significantly to the accumulation of photosynthatesby the pith alone. The bulk of enhanced photosynthate accumulationby the remaining stem tissues can be accounted for by a GA,-inducedelevation of the apoplast sucrose concentration. In terms ofonset and change in rate, the time-course kinetics of GA3 stimulationof [14C]photosynthate transport and of in vitro [14CJsucroseuptake were found to be similar. It is proposed that GA3 promotionof photosynthate accumulation by the pith tissues is a minorcontributing factor to GA3 regulation of phloem translocation Phaseolus vulgaris L., french bean, stem, assimilate transport, gibberellic acid, rink accumulation 相似文献
5.
Differential filtration was used to apportion [32p]orthophosphate(P1) uptake to predominantly bacterial (<3 µm) or algal(>3 µm) components of Lake Kinneret microplankton.Bacteria generally showed preferential 32Pi uptake in comparisonwith algae. Nevertheless, in most cases, the relative proportionof 32P counts retained on 3 µm filters was greater thanthe proportion of 14C counts from heterotrophic bacterial incorporationof [14Clglucose, indicating that algae were competing for Piwith bacteria with some measure of success. Most time courseexperiments did not show any consistent transfer of 32P frombacteria to algae. The addition of a bacterial inhibitor (garamycin)caused a relative increase in the proportion of algal to bacterial32Pi uptake. Added organic P substrates lowered the amount of32Pi uptake and appeared to be preferentially utilized by bacteria.Apparent residence times for Pi in Lake Kinneret ranged from0.4 h (prior to overturn) to 17.4 h during bomothermy. Despitelow ambient Pi concentrations, P limitation in Lake Kinneretis not as extreme as in many other aquatic environments. 相似文献
6.
de S. WAIDYANATHA U. P.; KEYS A. J.; WHITTINGHAM C. P. 《Journal of experimental botany》1975,26(1):15-26
When solutions of [14C]glycollate, glycine, serine, glycerate,or glucose were supplied to segments of wheat leaves throughtheir cut bases in the light, most of the 14C was incorporatedinto sucrose in air but in CO2-free air less sucrose was made.The synthesis of sucrose was decreased because metabolism ofserine was partly blocked. Sucrose synthesis from glucose andglycerate in CO2-free air was decreased but to a smaller extent;relatively more CO2 was evolved and serine accumulated. Theeffects of DCMU and light of different wavelengths on metabolismby leaves of L-[U-14C]serine confirmed that simultaneous photosyntheticassimilation of carbon was necessary for the conversion of serineto sucrose. Of various products of photosynthesis fed exogenouslyto the leaves -keto acids were the most effective in promotingphotosynthesis of sucrose and release of 14CO2 from 14C-labelledserine. This suggests that in CO2-free air the metabolism ofserine may be limited by a shortage of -keto acid acceptorsfor the amino group. In CO2-free air added glucose stimulatedproduction of CO2 and sucrose from D-[U-14C]- glycerate andno competitive effects were evident even though glucose is convertedrapidly to sucrose under these conditions. In addition to asupply of keto acid, photosynthesis may also provide substratesthat can be degraded and provide energy in the cytoplasm forthe conversion of glycerate to sugar and phosphates and sucrose. 相似文献
7.
Tritiated GA1 and four of its synthetic derivatives were studiedin relation to their biological activity, uptake and metabolismby barley aleurone layers. Incubation was done in the presenceand absence of ABA. Tentative identification of some of themetabolites was made by TLC and GLC radiocounting of the metaboliteand its acid hydrolyzed derivative. Only GA1 promoted -amylase synthesis. Uptake ranged from 20to 42%, varying with the derivative. ABA enhanced uptake of[3H]GA1 and [3H]pseudoGA1 and inhibited uptake of [3H]ketoGA1the Wagner-Meerwein rearrangement product of [3H]GA1 Uptakeof [3H]GA1 methyl ester ([3H]GA1-Me) and [3H]dihydroGA1 wasunaffected by ABA. [3H]GA1 was converted to an amphoteric GA1 derivative ([3H]amphoGA1)and [3H]GA1-glycosyl ester. GA1-Me was metabolized to four products,all of them GA1 derivatives, including an apparent amphotericGA1 derivative. DihydroGA1 was quite stable; only one metabolitewas produced in sufficient yield to analyze. This product didnot cochromatograph with either of the expected acid hydrolyzedepimers of [3H]dihydroGA1. [3H]ketoGA1 was readily metabolizedto one product, probably the glycoside. [3H]pseudoGA1 remainedessentially unmetabolized. Metabolism of all compounds testedwas not dramatically affected by ABA. Surprisingly, no metabolitesfrom hydroxylation at the 2-position were found.
1 Present address: Monsanto Agricultural Co., 800 N. LindberghBlvd., St. Louis, MO 63166, U.S.A. (Received January 31, 1977; ) 相似文献
8.
Bitter stimuli induce Ca2+ signaling and CCK release in enteroendocrine STC-1 cells: role of L-type voltage-sensitive Ca2+ channels 总被引:3,自引:0,他引:3
Chen MC Wu SV Reeve JR Rozengurt E 《American journal of physiology. Cell physiology》2006,291(4):C726-C739
We previously demonstrated the expression of bitter taste receptors of the type 2 family (T2R) and the -subunits of the G protein gustducin (Ggust) in the rodent gastrointestinal (GI) tract and in GI endocrine cells. In this study, we characterized mechanisms of Ca2+ fluxes induced by two distinct T2R ligands: denatonium benzoate (DB) and phenylthiocarbamide (PTC), in mouse enteroendocrine cell line STC-1. Both DB and PTC induced a marked increase in intracellular [Ca2+] ([Ca2+]i) in a dose- and time-dependent manner. Chelating extracellular Ca2+ with EGTA blocked the increase in [Ca2+]i induced by either DB or PTC but, in contrast, did not prevent the effect induced by bombesin. Thapsigargin blocked the transient increase in [Ca2+]i induced by bombesin, but did not attenuate the [Ca2+]i increase elicited by DB or PTC. These results indicate that Ca2+ influx mediates the increase in [Ca2+]i induced by DB and PTC in STC-1 cells. Preincubation with the L-type voltage-sensitive Ca2+ channel (L-type VSCC) blockers nitrendipine or diltiazem for 30 min inhibited the increase in [Ca2+]i elicited by DB or PTC. Furthermore, exposure to the L-type VSCCs opener BAY K 8644 potentiated the increase in [Ca2+]i induced by DB and PTC. Stimulation with DB also induced a marked increase in the release of cholecystokinin from STC-1 cells, an effect also abrogated by prior exposure to EGTA or L-type VSCC blockers. Collectively, our results demonstrate that bitter tastants increase [Ca2+]i and cholecystokinin release through Ca2+ influx mediated by the opening of L-type VSCCs in enteroendocrine STC-1 cells. type 2 family taste receptors; gastrointestinal peptides; phospholipase C 2; Ca2+ fluxes; enteroendocrine cells; cholecystokinin secretion 相似文献
9.
Effect of beta -adrenoceptor activation on [Ca2+]i regulation in murine skeletal myotubes 总被引:1,自引:0,他引:1
Prakash Y. S.; van der Heijden H. F.M.; Gallant E. M.; Sieck G. C. 《American journal of physiology. Cell physiology》1999,276(5):C1038
The presentstudy used real-time confocal microscopy to examine the effects of the2-adrenoceptor agonistsalbutamol on regulation of intracellularCa2+ concentration([Ca2+]i)in myotubes derived from neonatal mouse limb muscles.Immunocytochemical staining for ryanodine receptors and skeletal musclemyosin confirmed the presence of sarcomeres. The myotubes displayedboth spontaneous and ACh-induced rapid (<2-ms rise time)[Ca2+]itransients. The[Ca2+]itransients were frequency modulated by both low and high concentrations of salbutamol. Exposure to -bungarotoxin and tetrodotoxin inhibited ACh-induced[Ca2+]itransients and the response to low concentrations of salbutamol but notthe response to higher concentrations. Preexposure to caffeineinhibited the subsequent[Ca2+]iresponse to lower concentrations of salbutamol and significantly blunted the response to higher concentrations. Preexposure to salbutamol diminished the[Ca2+]iresponse to caffeine. Inhibition of dihydropyridine-sensitive Ca2+ channels with nifedipine orPN-200-110 did not prevent[Ca2+]ielevations induced by higher concentrations of salbutamol. The effectsof salbutamol were mimicked by the membrane-permeant analog dibutyryladenosine 3',5'-cyclic monophosphate. Thesedata indicate that salbutamol effects in skeletal muscle predominantly involve enhanced sarcoplasmic reticulumCa2+ release. 相似文献
10.
The metabolic transformation of glycolate to glycine occurringin photosynthesizing cells of Chromatium was investigated bythe radioisotopic technique and by amino acid analysis. By analyzingthe distribution of radiocarbon upon feeding [1-14C] glycolate,[2-14C] glyoxylate and [1-14C] glycine to bacterial cells, itwas demonstrated that glycolate is converted to glycinc viaglyoxylate, and both glycolate and glycine are excreted extracellularly.Although the formation of serine was barely detected by theabove two techniques in both N2 and O2 atmospheres, it was foundthat 14CO2 is evolved quite markedly from both [1-14C] glycolateand [1-14C] glycine fed to the Chromatium cells. Analyticalresults of transient changes in amino acid compositions underatmospheric changes of N2O2 and by the addition of exogenousglycolate in N2 confirm the notion that glycolate is convertedto glycine. Acidic amino acids (glutamic acid and aspartic acid)appear to take part in glycine formation as amino donors. Theformation of glycine from glycolate in a N2 atmosphere suggeststhat an unknown glycolate dehydrogenation reaction may operatein the overall process.
1 This is paper XXXVII in the series Structure and Functionof Chloroplast Proteins. Paper XXXVI is ref. (5). Theresearch was supported in part by grants from the Ministry ofEducation of Japan (No. 111912), the Toray Science Foundation(Tokyo) and the Naito Science Foundation (Tokyo). (Received July 14, 1976; ) 相似文献
11.
Extracellular ATP plays an important role in the regulation of renal function. However, the effect of ATP on the Na+-glucose cotransporters (SGLTs) has not been elucidated in proximal tubule cells (PTCs). Therefore, this study was performed to examine the action of ATP on SGLTs and their related signal pathways in primary cultured rabbit renal PTCs. ATP increased [14C]--methyl-D-glucopyranoside (-MG) uptake in a time-dependent (>1 h) and dose-dependent (>106 M) manner. ATP stimulated -MG uptake by increasing in Vmax without affecting Km. ATP-induced increase of -MG uptake was correlated with the increase in both SGLT1 and SGLT2 protein expression levels. ATP-induced stimulation of -MG uptake was blocked by suramin (nonspecific P2 receptor antagonist), RB-2 (P2Y receptor antagonist), and MRS-2179 (P2Y1 receptor antagonist), suggesting a role for the P2Y receptor. ATP-induced stimulation of -MG uptake was blocked by pertussis toxin (PTX, a Gi protein inhibitor), SQ-22536 (an adenylate cyclase inhibitor), and PKA inhibitor amide 14-22 (PKI). ATP also increased cAMP formation, which was blocked by PTX and RB-2. However, pretreatment of adenosine deaminase did not block ATP-induced cAMP formation. In addition, ATP-induced stimulation of -MG uptake was blocked by SB-203580 (p38 MAPK inhibitor), but not by PD-98059 (p44/42 MAPK inhibitor) or SP-600125 (JNK inhibitor). Indeed, ATP induced phosphorylation of p38 MAPK. In conclusion, ATP increases -MG uptake via cAMP and p38 MAPK in renal PTCs. adenosine 5'-triphosphate; mitogen-activated protein kinase 相似文献
12.
Nobe H Nobe K Fazal F De Lanerolle P Paul RJ 《American journal of physiology. Cell physiology》2003,284(3):C599-C606
Fibroblasts form fibers when grown inculture medium containing native type 1 collagen. The contractileforces generated can be precisely quantified and used to analyze thesignal transduction pathways regulating fibroblast contraction. Calfserum (30%) induces a sustained contraction that is accompanied by atransient increase in intracellular calcium([Ca2+]i). W-7, a calmodulin inhibitor,KN-62, an inhibitor of calcium/calmodulin-dependent protein kinase, andML-7, a myosin light-chain kinase inhibitor, had no effects on eitherthe contraction or the [Ca2+]i responses.Neither genistein, a tyrosine kinase inhibitor, nor calphostin C, aprotein kinase C inhibitor, had major effects on force or[Ca2+]i. In contrast, the Rho kinaseinhibitors(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632) and HA1077 depressed the contraction in a dose-dependent manner without affecting the [Ca2+]iresponse. Stress fiber formation was also suppressed by Y-27632. Surprisingly, calf serum, Y-27632, and calf serum plus Y-27632 did notalter mono- or diphosphorylation of the myosin regulatory light chain(MRLC) compared with control untreated fibers. These results suggestthat the sustained contraction of NIH 3T3 fibroblast fibers induced bycalf serum is mediated by Rho kinase but is independent of a sustainedincrease in [Ca2+]i, calcium/calmodulin- orprotein kinase C-dependent pathways, or increases in MRLC phosphorylation. 相似文献
13.
Ca2+-dependent inhibition of NHE3 requires PKC alpha which binds to E3KARP to decrease surface NHE3 containing plasma membrane complexes 总被引:1,自引:0,他引:1
Lee-Kwon W Kim JH Choi JW Kawano K Cha B Dartt DA Zoukhri D Donowitz M 《American journal of physiology. Cell physiology》2003,285(6):C1527-C1536
The intestinal brush border (BB) Na+/H+ exchanger isoform 3 (NHE3) is acutely inhibited by elevation in the concentration of free intracellular Ca2+ ([Ca2+]i) by the cholinergic agonist carbachol and Ca2+ ionophores in a protein kinase C (PKC)-dependent manner. We previously showed that elevating [Ca2+]i with ionomycin rapidly inhibited NHE3 activity and decreased the amount of NHE3 on the plasma membrane in a manner that depended on the presence of the PDZ domain-containing protein E3KARP (NHE3 kinase A regulatory protein, also called NHERF2). The current studies were performed in PS120 fibroblasts (NHE-null cell line) stably transfected with NHE3 and E3KARP to probe the mechanism of PKC involvement in Ca2+ regulation of NHE3. Pretreatment with the general PKC inhibitor, GF109203X prevented ionomycin inhibition of NHE3 without altering basal NHE3 activity. Similarly, the Ca2+-mediated inhibition of NHE3 activity was blocked after pretreatment with the conventional PKC inhibitor Gö-6976 and a specific PKC pseudosubstrate-derived inhibitor peptide. [Ca2+]i elevation caused translocation of PKC from cytosol to membrane. PKC bound to the PDZ1 domain of GST-E3KARP in vitro in a Ca2+-dependent manner. PKC and E3KARP coimmunoprecipitated from cell lysates; this occurred to a lesser extent at basal [Ca2+]i and was increased with ionomycin exposure. Biotinylation studies demonstrated that [Ca2+]i elevation induced oligomerization of NHE3 in total lysates and decreased the amount of plasma membrane NHE3. Treatment with PKC inhibitors did not affect the oligomerization of NHE3 but did prevent the decrease in surface amount of NHE3. These results suggest that PKC is not necessary for the Ca2+-dependent formation of the NHE3 plasma membrane complex, although it is necessary for decreasing the membrane amounts of NHE3, probably by stimulating NHE3 endocytosis. Na absorption; PDZ domains; signal complex 相似文献
14.
Age-related differences in Na+-dependent Ca2+ accumulation in rabbit hearts exposed to hypoxia and acidification 总被引:1,自引:0,他引:1
Anderson SE Liu H Ho HS Lewis EJ Cala PM 《American journal of physiology. Cell physiology》2003,284(5):C1123-C1132
In this study, we test the hypothesisthat in newborn hearts (as in adults) hypoxia and acidificationstimulate increased Na+ uptake, in part via pH-regulatoryNa+/H+ exchange. Resulting increases inintracellular Na+ (Nai) alter the force drivingthe Na+/Ca2+ exchanger and lead to increasedintracellular Ca2+. NMR spectroscopy measuredNai and cytosolic Ca2+ concentration([Ca2+]i) and pH (pHi) inisolated, Langendorff-perfused 4- to 7-day-old rabbit hearts. AfterNa+/K+ ATPase inhibition, hypoxic hearts gainedNa+, whereas normoxic controls did not [19 ± 3.4 to139 ± 14.6 vs. 22 ± 1.9 to 22 ± 2.5 (SE) meq/kg drywt, respectively]. In normoxic hearts acidified using theNH4Cl prepulse, pHi fell rapidly and recovered,whereas Nai rose from 31 ± 18.2 to 117.7 ± 20.5 meq/kg dry wt. Both protocols caused increases in [Ca]i;however, [Ca]i increased less in newborn hearts than inadults (P < 0.05). Increases in Nai and[Ca]i were inhibited by theNa+/H+ exchange inhibitormethylisobutylamiloride (MIA, 40 µM; P < 0.05), aswell as by increasing perfusate osmolarity (+30 mosM) immediately before and during hypoxia (P < 0.05). The data supportthe hypothesis that in newborn hearts, like adults, increases inNai and [Ca]i during hypoxia and afternormoxic acidification are in large part the result of increased uptakevia Na+/H+ and Na+/Ca2+exchange, respectively. However, for similar hypoxia and acidification protocols, this increase in [Ca]i is less in newborn thanadult hearts. 相似文献
15.
Huang C Hujer KM Wu Z Miller RT 《American journal of physiology. Cell physiology》2004,286(1):C22-C30
The Ca2+-sensing receptor (CaR) couples to multiple G proteins involved in distinct signaling pathways: Gi to inhibit the activity of adenylyl cyclase and activate ERK, Gq to stimulate phospholipase C and phospholipase A2, and G to stimulate phosphatidylinositol 3-kinase. To determine whether the receptor also couples to G12/13, we investigated the signaling pathway by which the CaR regulates phospholipase D (PLD), a known G12/13 target. We established Madin-Darby canine kidney (MDCK) cell lines that stably overexpress the wild-type CaR (CaRWT) or the nonfunctional mutant CaRR796W as a negative control, prelabeled these cells with [3H]palmitic acid, and measured CaR-stimulated PLD activity as the formation of [3H]phosphatidylethanol (PEt). The formation of [3H]PEt increased in a time-dependent manner in the cells that overexpress the CaRWT but not the CaRR796W. Treatment of the cells with C3 exoenzyme inhibited PLD activity, which indicates that the CaR activates the Rho family of small G proteins, targets of G12/13. To determine which G protein(s) the CaR couples to in order to activate Rho and PLD, we pretreated the cells with pertussis toxin to inactivate Gi or coexpressed regulators of G protein-signaling (RGS) proteins to attenuate G protein signaling (RGS4 for Gi and Gq, and a p115RhoGEF construct containing the RGS domain for G12/13). Overexpression of p115RhoGEF-RGS in the MDCK cells that overexpress CaRWT inhibited extracellular Ca2+-stimulated PLD activity, but pretreatment of cells with pertussis toxin and overexpression of RGS4 were without effect. The involvement of other signaling components such as protein kinase C, ADP-ribosylation factor, and phosphatidylinositol biphosphate was excluded. These findings demonstrate that the CaR couples to G12/13 to regulate PLD via a Rho-dependent mechanism and does so independently of Gi and Gq. This suggests that the CaR may regulate cytoskeleton via G12/13, Rho, and PLD. calcium-sensing receptor; G proteins; RGS proteins 相似文献
16.
Inflammatory cytokines (IL-1alpha , TNF-alpha ) and LPS modulate the Ca2+ signaling pathway in osteoblasts 总被引:2,自引:0,他引:2
Tam Vincent K.; Schotland Sandra; Green Jacob 《American journal of physiology. Cell physiology》1998,274(6):C1686
Locally derived growth factors and cytokines in bone play acrucial role in the regulation of bone remodeling, i.e., bone formationand bone resorption processes. We studied the effect of interleukin(IL)-1, tumor necrosis factor (TNF)-, andEscherichia coli lipopolysaccharide(LPS) on the hormone-activatedCa2+ message system in theosteoblastic cell line UMR-106 and in osteoblastic cultures derivedfrom neonatal rat calvariae. In both cell preparations, IL-1,TNF-, and LPS did not alter basal intracellularCa2+ concentration([Ca2+]i)but attenuated Ca2+ transientsevoked by parathyroid hormone (PTH) andPGE2 in a dose (1-100 ng/ml)-and time (8-24 h)-dependent fashion. The cytokines modulatedhormonally induced Ca2+ influx(estimated by using Mn2+ as asurrogate for Ca2+) as well asCa2+ mobilization fromintracellular stores. The latter was linked to suppressed production ofhormonally induced inositol 1,4,5-trisphosphate. The effect ofcytokines on[Ca2+]iwas abolished by the tyrosine kinase inhibitor herbimycin A (50 ng/ml).The cytokine's effect was, however, independent of nitric oxide (NO)production, since NO donors (sodium nitroprusside) as well as permeablecGMP analogs augment, rather than attenuate, hormonally inducedCa2+ transients in osteoblasts.Given the stimulatory role of cytokines on NO production inosteoblasts, the disparate effects of cytokines and NO on theCa2+ signaling pathway may servean autocrine/paracrine mechanism for modulating the effect ofcalciotropic hormones on bone metabolism. 相似文献
17.
After removal of the embryo from developing seeds of Pisum sativum,the empty ovules (seed coats without enclosedembryo) were filled with a solution (pH 5.5) containing mannitol(usually 400 mM) to which various salts were added. A solutioncontaining two isotopes ((a) [2H]-sucrose/[14C]aminoisobutyricacid (AIB) or (b) [3H]valine/[14C]asparagine mixture) was administeredto the plant via the petiole subtending the fruiting node, and[2H]solute and [14C]solute unloading from the seed coat wasmeasured, in pulse-labelling experiments of about 5 h. The presenceof 25 or 50 mM K+ in the empty ovule enhancedthe release of sucrose from the seed coat particularly duringthe first hours of the experiment, but the stimulating effectof K+ on the release of labelled solutes derived from aminoacids was much smaller. The presence of 25 mM CaCl2 did notaffect the release of sucrose or amino acids from the seed coat.The effect of K+ on sucrose and amino acid release is explainedas an inhibition of sucrose and amino acid resorption from theseed coat apoplast into seed coat cells, after unloading fromthe seed coat unloading sites. It is suggested that amino acidrelease is much less affected by K+ than sucrose release, becausefar less resorption of amino acids by seed coat parenchyma cellstakes place during amino acid transport into the seed coat cavity. Pisum sativum, pea, assimilate transport, assimilate unloading, seed-coat exudate, seed development, sucrose resorption, surgical treatment 相似文献
18.
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
19.
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
20.
EGF inhibits muscarinic receptor-mediated calcium signaling in a human salivary cell line 总被引:1,自引:0,他引:1
Zhang BX Yeh CK Hymer TK Lifschitz MD Katz MS 《American journal of physiology. Cell physiology》2000,279(4):C1024-C1033
The effects of epidermal growth factor(EGF) on intracellular calcium ([Ca2+]i)responses to the muscarinic agonist carbachol were studied in a humansalivary cell line (HSY). Carbachol (104 M)-stimulated[Ca2+]i mobilization was inhibited by 40%after 48-h treatment with 5 × 1010 M EGF. EGF alsoreduced carbachol-induced [Ca2+]i inCa2+-free medium and Ca2+ influx followingrepletion of extracellular Ca2+. UnderCa2+-free conditions, thapsigargin, an inhibitor ofCa2+ uptake to internal stores, induced similar[Ca2+]i signals in control and EGF-treatedcells, indicating that internal Ca2+ stores were unaffectedby EGF; however, in cells exposed to thapsigargin, Ca2+influx following Ca2+ repletion was reduced by EGF.Muscarinic receptor density, assessed by binding of the muscarinicreceptor antagonistL-[benzilic-4,4'-3HCN]quinuclidinyl benzilate([3H]QNB), was decreased by 20% after EGF treatment.Inhibition of the carbachol response by EGF was not altered by phorbolester-induced downregulation of protein kinase C (PKC) but was enhancedupon PKC activation by a diacylglycerol analog. Phosphorylation of mitogen-activated protein kinase (MAP kinase) and inhibition of thecarbachol response by EGF were both blocked by the MAP kinase pathwayinhibitor PD-98059. The results suggest that EGF decreases carbachol-induced Ca2+ release from internal stores andalso exerts a direct inhibitory action on Ca2+ influx. Adecline in muscarinic receptor density may contribute to EGF inhibitionof carbachol responsiveness. The inhibitory effect of EGF is mediatedby the MAP kinase pathway and is potentiated by a distinct modulatorycascade involving activation of PKC. EGF may play a physiological rolein regulating muscarinic receptor-stimulated salivary secretion. 相似文献