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1.
Da Silva N Shum WW El-Annan J Păunescu TG McKee M Smith PJ Brown D Breton S 《American journal of physiology. Cell physiology》2007,293(1):C199-C210
An acidic luminal pH in the epididymis contributes to maintaining sperm quiescent during their maturation and storage. The vacuolar H+ATPase (V-ATPase), located in narrow and clear cells, is a major contributor to luminal acidification. Mutations in one of the V-ATPase subunits, ATP6v1B1 (B1), cause distal renal tubular acidosis in humans but surprisingly, B1/ mice do not develop metabolic acidosis and are fertile. While B1 is located in the apical membrane of narrow and clear cells, the B2 subunit localizes to subapical vesicles in wild-type mouse, rat and human epididymis. However, a marked increase (84%) in the mean pixel intensity of B2 staining was observed in the apical pole of clear cells by conventional immunofluorescence, and relocalization into their apical membrane was detected by confocal microscopy in B1/ mice compared with B1+/+. Immunogold electron microscopy showed abundant B2 in the apical microvilli of clear cells in B1/ mice. B2 mRNA expression, determined by real time RT-PCR using laser-microdissected epithelial cells, was identical in both groups. Semiquantitative Western blots from whole epididymis and cauda epididymidis showed no variation of B2 expression. Finally, the luminal pH of the cauda epididymidis was the same in B1/ mice as in B1+/+ (pH 6.7). These data indicate that whereas overall expression of B2 is not affected in B1/ mice, significant redistribution of B2-containing complexes occurs from intracellular compartments into the apical membrane of clear cells in B1/ mice. This relocation compensates for the absence of functional B1 and maintains the luminal pH in an acidic range that is compatible with fertility. male reproductive tract; male fertility; luminal acidification; proton pump; vacuolar H+ATPase 相似文献
2.
Characterization of the vacuolar-type H+-ATPase from guard cell protoplasts of Commelina 总被引:1,自引:0,他引:1
Willmer C.M.; Grammatikopoulos G.; Lascve G.; Vavasseur A. 《Journal of experimental botany》1995,46(4):383-389
Characteristics of the vacuolar-type (V-type) H+-ATPase fromguard cell protoplasts of Commelina communis L. were investigatedusing a linked enzyme assay and nitrate inhibition as a diagnosticindicator of the enzyme activity. ATPase activity was completelyinhibited by about 50 mol m3 nitrate and activity wasoptimal near pH 8.0. The temperature optimum for activity wasabout 37 C and an Arrhenius plot indicated changes in activationenergy for the ATPase at 15C and possibly at about 30 C. Theenzyme was stimulated by Cl while Ca2+ inhibited activity(l50 = 1.5 mol m3). The apparent Km (MgATP) was 0.62mol m3. Incubation of guard cell protoplasts for up to 5 h in 50 µMabscisic acid (ABA) or 25µM fusicoccin (FC) did not affectsubsequent ATPase activity. In vitro assays with FC or ABA alsodid not affect enzyme activity. Activity was not affected bylight or potassium ferricyanide, two factors which are knownto influence stomatal activity. Beticoline was a potent inhibitorof activity (l50 = 50 µM) while DCCD was less effective(l50 = 90µM). On chlorophyll, protein and protoplast bases, V-type ATPaseactivity was greater in guard cell protoplasts than mesophyllcell protoplasts by 66, 13.9 and 1.9, respectively. On atonoplast surface area basis the enzyme activity was 5.6 timeshigher in guard cell protoplasts than in mesophyll cell protoplasts Thus, although the characteristics of the V-type, H +-ATPaseof GCP are very similar to those found in other cell types,rates of activity and probably tonoplast enzyme density aremuch greater in guard cell protoplasts than mesophyll cell protoplastsof C. communis which corresponds with the large and rapid ionfluxes across the tonoplast associated with stomatal movements Key words: Guard cell protoplasts, stomata, V-type H +-ATPase 相似文献
3.
Effects of Two Plasmalemma ATPase Inhibitors on H+ Extrusion and Intracellular pH in Elodea densa Leaves 总被引:2,自引:0,他引:2
Beffagna, N. and Romani, G. 1988. Effects of two plasmalemmaATPase inhibitors on H+ extrusion and intracellular pH in Elodeadensa leaves.J. exp. Bot. 39: 10331043. Elodea leaves in the dark show very little exchange of H+ withthe medium in the external pH range between 5.0 and 6.0. Thepresence of fusicoccin and potassium in the medium markedlystimulates H+ extrusion. Fusicoccin- and K+ -induced H+ extrusionis inhibited by either erythrosin B (EB) or Na-orthovanadate,two inhibitors of H+ transporting plasma membrane ATPase. EBcompletely inhibits it from the first 30 min of treatment, whensupplied at pH 5.5 at a concentration of 30 mmol m3.Vanadate also inhibits H+ extrusion, this effect becoming evidentonly after 45 min of treatment. After this time inhibition iscomplete with 250 mmol m3 vanadate but only partial forlower concentrations. In the presence of either inhibitor the intracellular pH, measuredas cell sap pH, is significantly lowered. When the intracellularpH changes are determined on vacuole and, separately, on cytoplasmby the weak acid and base distribution method, acidificationof both compartments is found to accompany the blocking of H+extrusion by either of the inhibitors. Key words: Intracellular pH, vanadate, erythrosin B, H+pumping 相似文献
4.
When microsomal membranes from maize (Zea mays L. cv. Clipper)coleoptiles were separated by isopyc-nic centrifugation on acontinuous 1045% sucrose gradient, bafilomycin A1-inhibitedATPase activity co-localized with the activities of the tonoplastmarker-enzymes, nitrate-Inhibited ATPase and K+-dependent pyrophosphatase.Thus, bafilomycin A1 is a specific inhibitor of the vacuolarH+-ATPase of maize coleoptiles. Inhibition of the vacuolar H+-ATPaseby bafilomycin A1 was strictly dependent upon the concentrationof the enzyme present in the assay medium, suggesting a stoichiometricassociation between bafilomycin A1 and the vacuolar H+-ATPase.In tonoplast-enriched preparations, half-maximal inhibitionwas obtained at 43 pmol bafilomycin A1 mg1 protein. BafilomycinA1 inhibited the vacuolar H+-ATPase in a simple non-competitivemanner: increasing bafilomycin A1 concentrations reduced theVmax, of the H+ -ATPase, but had no effect on its Km towardsATP. Key words: Bafilomycin A1, coleoptile, H+-ATPase (vacuolar), maize, Zea mays L 相似文献
5.
6.
Calcium Inhibits Ion-Stimulated Stomatal Opening in Epidermal Strips of Commelina communis L. 总被引:2,自引:0,他引:2
Inoue, H. and Katoh, Y. 1987. Calcium inhibitsion-stimulatedstomatal opening in epidermal strips of Commelina communis L.J.exp. Bot. 38: 142149. Ca2+ suppressed both the ion-stimulated stomatal opening andH+ extrusion of pre-illuminated epidermal strips isolated fromCommelina communis L. In the absence of Ca2+, the rate of H+release was 18 nmol H+ cm2 h1 per epidermal stripunit area in 150 mol m3 KCL at pH 7?4. Half-maximum inhibitionof stomatal opening was observed with 220 mmol m3 ofCa2+. The hexavalent dye, ruthenium red, showed concentration-dependentprevention of the inhibition by Ca2+ of the ion-stimulated stomatalopening. The effect of ruthenium red was non-competitive, andthe K1 for the calcium inhibition was found to be 3?6 mmol m3.The calcium inhibition of H+ extrusion was also prevented byruthenium red. These results suggest that Ca2+ inhibits theactivity of electrogenic H+ translocating ATPase of the guardcell plasma membrane and leads to the suppression of stomatalopening. Key words: Calcium, Commelina communis, ruthenium red, stomata 相似文献
7.
Faraday Christopher D.; Spanswick Roger M.; Bisson Mary A. 《Journal of experimental botany》1996,47(4):589-594
Plasma membranes were isolated using the aqueous polymer two-phasepartition method from the algae Chara corallina and Chara longifolia,algae which differ in their ability to grow in saline environments.Enrichment of plasma membrane and depletion of tonoplast relativeto the microsomal fraction was monitored using phosphohydrolaseassays and crossreactions to antibodies raised against higherplant transporters. Antibodies to the vacuolar ATPase and pyrophosphatasecross-reacted with epitopes in the microsomal fraction, butshowed little affinity for the plasma membrane fraction. Pyrophosphataseactivity also declined in the plasma membrane fraction relativeto the microsomal fraction. The V-type H+ -ATPase activity,sensitive to nitrate or bafilomycin, was low in both fractions,though the cross-reaction to the antibody was reduced in theplasma membrane fraction. By contrast, the antibody recognitionof a P-type H+-ATPase amino acid sequence from Arabidopsis didnot occur strongly in the anticipated 90100 kDa range.While there was enhanced recognition of a polypeptide at around140 kDa in the plasma membrane fraction, salt treatment of Charalongifolia resulted in plasma membrane fractions with reducedamounts of this epitope, but no change in vanadate-sensitiveATPase activity, suggesting that it does not represent the onlyP-type ATPase. Microsomal membranes from saltadapted C. longifoliahave higher reactivity with the antibody to the tonoplast ATPase. Key words: Chara, plasma membrane, salt tolerance, ATPase 相似文献
8.
Membrane-bound Mg++-activated ATPase activity in epidermal stripsfrom tobacco leaves (Nicotiana tabacum L. Samsun NN) was stimulatedby abscisic acid (ABA) when the strips were floated on ABA solutionin light or in darkness. The optimum ABA concentrations in lightand in darkness were 105 M and 106 M, respectively.Carbonyl cyanide m-chlorophenylhydrazone (CCCP) and N, N'-dicyclohexylcarbodiimide(DCCD) completely blocked the basal level membrane-bound epidermalATPase activity. ABAinduced membrane-bound epidermal ATPaseactivity was completely inhibited by CCCP, but only partly byDCCD. H+-influx into epidermal strips on a solution in light was lowerthan that in darkness. ABA stimulated H+-influx into epidermalstrips in light and in darkness. CCCP suppressed basal levelH+-influx, whereas DCCD did not. CCCP also suppressed ABA-inducedH+-influx, whereas DCCD did not. Interaction between H+-influxand membranebound epidermal ATPase activity is discussed. (Received May 23, 1978; ) 相似文献
9.
H+ translocation driven by NO3, NO2 and N2O reductionswith endogenous substrates in cells of Rhodopseudomonas sphaeroidesforma sp. denitrificans was investigated by the oxidant pulsemethod. Upon injection of nitrogenous oxides to anaerobic cellsin darkness, an alkaline transient in the external medium wasobserved, followed by acidification. The alkaline transientwas enhanced by carbonyl cyanide m-chlorophenylhydrazone. When a viologen dye was used as an electron donor in the presenceof 1 mM Af-ethylmaleimide and 0.1 mM 2-n-heptyl-4-hydroxyquinoline-N-oxideto preclude respiration-linked H+ extrusion, addition of KNO3,KNO2 and N2O caused only a rapid alkalinization. The H+ consumptionstoichiometries, H+/2e ratios for NO3 reductionto NO2, NO2 reduction to 1/2 N2O and N2O reductionto N2 were 1.90, 3.18 and 2.04, respectively.These values agreed well with the fact that all reductions ofnitrogenous oxides in denitrification occur on the periplasmicside of the cytoplasmic membrane. When corrected for H+ consumption in the periplasm, the H+ extrusionstoichiometries, H+/2e ratios with endogenous substratesin the presence of K+/valinomycin for NO3 reduction toNO2, NO2 reduction to 1/2 N2O and N2O reductionto N2 were 4.05, 4.95 and 6.01, respectively. (Received August 4, 1982; Accepted January 13, 1983) 相似文献
10.
An attempt has been made to quantify the light-induced H+ effluxand influx observed in polar leaves of Potamogeton lucens.Theseproton fluxes are spatially separated. The H+ efflux, mediatedby a plasmalemma bound H+ ATPase, occurs across theplasmamembrane at the morphological lower epidermis and is accompaniedby an H+ influx (or OH efflux) at the upper side oftheleaf. As a result, these leaves exhibit a remarkable pHpolarityin the light. The pH near the lower epidermis may drop to avalueas low as 3.5, while a pH of about 10.5 can be observed at theupper epidermis. Obviously this phenomenon requires thecoordinationof transport processes in the different cell layers of the leaftissue. These observations led to quantitative studies oftherelation between the H+ fluxes at either plasmalemma. Thesefluxes were calculated from the pH values recorded at twodistancesfrom the leaf surface. Although the H+ influx always exceededthe efflux, a coupling between the transport processesacrosseither plasma membrane became evident from the timecoursesof the two fluxes. Key words: Potamogeton lucens, proton flux, flux coupling, pH;polarity 相似文献
11.
H+ Efflux and Trans-Root Potential Measured while Increasing the Temperature of Solutions Bathing Excised Roots of Zea mays 总被引:1,自引:0,他引:1
Kennedy, C. D. and Gonsalves, F. A. N. 1988. H+ efflux and trans-rootpotential measured while increasing the temperature of solutionsbathing excised roots of Zea mays.J. exp. Bot. 39: 3749. Novel temperature-ramp procedures have been used to measureH+ efflux and trans-root potential of excised roots of Zea mays(var. Fronica). Two types of experiment were performed: (1),increasing temperature from 17°C, and (2), pre-cooling theroots to 1°C before starting the temperature ramp. The ratesof increase of temperature for H+ efflux and trans-root potentialexperiments were 0·5 and 2·1°C min1respectively The H+ scans revealed strong sharp maxima at 30°C and 32°C,for non-pre-cooled and pre-cooled roots respectively, the latterbeing significantly smaller. The trans-root potential scansfor the pre-cooled roots showed a corresponding maximum at 30°C,which was inhibited by KCN (1-0 mmol dm3) with or withoutSHAM (10 mmol dm3), or Hg2+ (1, 10, 100 µmol dm3)in the bathing solutions. Some of the evidence suggests thatthese maxima are associated with electrogenic H+ pumping, mediatedby a plasma membrane-bound ATPase. However, no correspondingmaximum was observed in the trans-root potential scans for non-pre-cooledroots, the potential remaining at about 75 m V from20°C to 35°C. As there is a 7-fold increase in H+ effluxbetween 20°C and 30°C, the relationship between netH+ efflux and electrogenic proton pumping in these roots isby no means clear. Some possibilities are considered here. Pre-cooled and non-pre-cooled roots show clear maxima in thetrans-root potential scans at about 46°C, at which temperaturethere is a slight net H+ influx. This, and other less prominentfeatures observed, are briefly discussed. Key words: H+ efflux, trans-root potential, temperature-ramp procedure, Zea mays, roots 相似文献
12.
The xylem vessels of excised adventitious roots of onion, Alliumcepa, were perfused with unbuffered nutrient solution adjustedinitially to either pH 9·3 or 3·9; the pH of thesolution after passage through the xylem, at rates not lessthan 2 xylem volume changes min1, was close to pH 6·5in both instances. The flux of H+ across the xylem/symplastboundary into mildly alkaline, phosphate-buffered solutionsperfusing the vessels could be increased greatly with increasingbuffer strength, up to a maximum value between 0·51·0pmol H+ mm2 s1. The apparent neutralization ofacidic malic acid buffers had a slightly lower maximum capacity,equivalent to 0·3 to 0·5 pmol H+mm2 s1. The addition of 5·0 pmol m3fusicoccin (FC) to the xylem perfusion solution stimulated theentry of H+ into the xylem; in unbuffered perfusion solutionsthe pH fell to pH 3·6 after a lag of 2535 min.FC additions to phosphate-buffered solutions also stimulatedthe H+ flux to an extent similar to that in unbuffered solution,viz. 0·20·4 pmol mm2 s1. The release of K+ (36Rb-labelled) into xylem sap transientlyincreased as the [K+] in weakly buffered perfusion solutionswas raised stepwise; a very marked increase being seen whenthe concentration was raised to 100 mol m3 from 40 molm3. The addition of 5·0 mmol m3 FC to theperfusing solution containing 100 mol m3 K+ rapidly decreasedthe K+ flux to the xylem as the H+ flux increased. Fusicoccinalso inhibited the flux of K+ into unbuffered perfusion solutionsbut the effect appeared reversible. Addition of 10 mmol m3abscisic acid (ABA) to the perfusion solution quickly producedtransient increases in both K+ and H+ fluxes into the xylem.In this and other experiments using weakly phosphate-bufferedperfusing solutions, H+ fluxes were comparable in size to thoseof K+ The results are consistent with the idea that the stele of onionroots contains a proton trarislocating ATPase whose activityresponds to the pH of the xylem sap. It is evident that theactivity of the proton secreting and proton neutralizing mechanismsin the xylem parenchyma control the movement of other ions acrossthe xylem/symplast boundary. Key words: Xylem perfusion, fusicoccin, abscisic acid, pH gradient 相似文献
13.
L-Leucine Transport in Isolated Protoplasts of Vinca Suspension Culture: Characterization of Uptake 总被引:1,自引:0,他引:1
The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H+ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The Km values of thethree affinity sites were 1.4 x 103 M, 1.3 x 104M, 4.3 x 105 M; the maximum velocity values were 3.3x 108, 4.5 x 109, 1.8 x 109 mol/10 min/4x 106 cells. (Received April 18, 1981; Accepted August 25, 1981) 相似文献
14.
Li G Yang Q Alexander EA Schwartz JH 《American journal of physiology. Cell physiology》2005,289(3):C665-C672
H+ transport in the collecting duct is regulated by exocytic insertion of H+-ATPase-laden vesicles into the apical membrane. The soluble N-ethylmaleimide-sensitive fusion protein attachment protein (SNAP) receptor (SNARE) proteins are critical for exocytosis. Syntaxin 1A contains three main domains, SNARE N, H3, and carboxy-terminal transmembrane domain. Several syntaxin isoforms form SNARE fusion complexes through the H3 domain; only syntaxin 1A, through its H3 domain, also binds H+-ATPase. This raised the possibility that there are separate binding sites within the H3 domain of syntaxin 1A for H+-ATPase and for SNARE proteins. A series of truncations in the H3 domain of syntaxin 1A were made and expressed as glutathione S-transferase (GST) fusion proteins. We determined the amount of H+-ATPase and SNARE proteins in rat kidney homogenate that complexed with GST-syntaxin molecules. Full-length syntaxin isoforms and syntaxin-1AC [amino acids (aa) 1264] formed complexes with H+-ATPase and SNAP23 and vesicle-associated membrane polypeptide (VAMP). A cassette within the H3 portion was found that bound H+-ATPase (aa 235264) and another that bound SNAP23 and VAMP (aa 190234) to an equivalent degree as full-length syntaxin. However, the aa 235264 cassette alone without the SNARE N (aa 1160) does not bind but requires ligation to the SNARE N to bind H+-ATPase. When this chimerical construct was transected into inner medullary collecting duct cells it inhibited intracellular pH recovery, an index of H+-ATPase mediated secretion. We conclude that within the H3 domain of syntaxin 1A is a unique cassette that participates in the binding of the H+-ATPase to the apical membrane and confers specificity of syntaxin 1A in the process of H+-ATPase exocytosis. soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor proteins; exocytosis; H++ transport 相似文献
15.
The correlation between the pump current and the ATP-dependentH+ efflux was examined in internodal cells of Nitellopsis obtusa.To control the cytoplasmic pH and ATP concentration, the tonoplastwas removed by intracellular perfusion with an EGTA-containingmedium. Two groups of perfused cells were prepared, one with1 mM ATP (+ATP cells) and the other without ATP but with hexokinaseand glucose (ATP cells). The ATP-dependent H+ effluxwas calculated as the difference in H+ efflux between the +ATPand ATP cells. Based on an electrically equivalent circuitmodel of the plasma membrane, the pump current was calculatedfrom the membrane potentials and the membrane resistances ofboth +ATP and ATP cells. When the membrane potentialwas not too high (220 mV), the ATP-dependent H+ current(19 mA m2) was almost equal to the pump current (20 mAm2) calculated from the electrical data. This indicatesthat the electrogenic pump current across the plasma membraneof Nitellopsis obtuse was mostly carried by H+. But when themembrane potential was high (280 mV), the H+ currentwas lower than the pump current. The possible cause of thisdiscrepancy is discussed. (Received November 5, 1984; Accepted February 28, 1985) 相似文献
16.
Mechanism of Photosynthate Efflux from Vicia faba L. Seed Coats 总被引:2,自引:0,他引:2
In order to develop a tentative model of the mechanism of photosynthateefflux from the vascular region of Vicia faba L. seed coats,wash-out experiments were performed after removal of the embryo. The sulphydryl group modifiers, pCMBS and NEM, reduced 14C-photosynthateefflux by 40% and 50%, respectively. Their inhibitory effectcould be prevented or reduced (in the latter case) by includingDTT in the bathing solution. Maltose competed with sucrose forefflux; a concentration of 300 mol m3 inhibited 14C-photosynthaterelease by 35%. The cations K+ , Na+ Mg2+ and TPP+ enhancedefflux significantly, whereas the countenon Cl had noeffect. The presence of the protonophore CCCP (0·1 molm3) led to a reduction of efflux by 50% net proton extrusiondropped by 34%. To a lesser extent, an efflux inhibition wasalso achieved by decreasing the cytoplasmic pH with the weakacid DM0. In contrast, alterations in the external pH causedonly a feeble response. The ATPase inhibitor, EB, decreasedphotosynthate efflux and H+ extrusion. DES reduced efflux slightly,presumably by affecting ATPase activity as well as energy metabolism. Based on these findings, it is proposed that a sucrose/protonantiport mechanism could be responsible for photosynthate effluxfrom Vicia faba seed coats. Key words: Photosynthate efflux, proton extrusion, proton/sucrose antiport, seed coat, Vicia faba L. 相似文献
17.
HARVEY WILLIAM R.; CIOFFI MOIRA; WOLFERSBERGER MICHAEL G. 《Integrative and comparative biology》1981,21(3):775-791
SYNOPSIS. We propose that particles, 715 nm in diameter,observed on the apical plasma membranes of cation transportingcells of insect midgut, salivary glands, and Malpighian tubulesare modified F1-F0 coupling complexes such as those found onphosphorylating membranes of mitochondria, chloroplasts, andbacteria. We suggest the generic term, portasome, to describeall of these particles and point out that they are located onthe side of the membrane which is electronegative and has thelow cation concentration, i.e., on the input side in each case.Biophysical evidence identifies the portasome bearing membraneas the ion transporting membrane in several insect epithelia,some of which exhibit ion modulated ATPase activity. The activityof a K+-modulated ATPase from Manduca sexta midgut is increasedin portasome enriched plasma membrane fractions. We proposethat portasomes orient the scalar hydrolysis of negatively chargedMgATP2 to less negatively charged MgADP thereby eliminatingthe attraction of MgATP2 to K+ with the result that theK+ ions are ejected to the opposite side of the portasome bearingmembrane. This mechanism explains the coupling of the scalarhydrolysis of ATP to the vectorial active transport of K+ whichleads to the establishment of a K+ electrochemical gradient.The reverse process, but with an H+ ionophore replacing a K+ionophore in the portasome, would provide a mechanism for couplingthe vectorial flow of H+, driven by a proton electrochemicalgradient, to scalar ATP synthesis and thereby provide a mechanismfor oxidative phosphorylation. Electrogenic active potassiumion transport would appear to have evolved from oxidative phosphorylation. 相似文献
18.
Ginzburg, M., and Ginzburg, B. Z., 1985. Ion and glycerol concentrationsin 12 isolates of Dunaliella.J. exp. Bot. 36: 10641074. Twelve isolates of Dunaliella with average cell volumes rangingfrom 50 to 1400x1018 m3 were grown in batch culture at0.5 M or 2.0 M NaCl. Glycerol and ions (Na+, K+, Mg2+, CI,phosphate) were measured in log-phase cultures. The contentsof Mg2+, K+ and phosphate per cell were found to be a functionof cell-volume. Cell glycerol, Na+ and Cl were functionsof cell-volume and of the NaCl concentration in the medium.Solute concentrations were calculated from the measured cell-volumesand from the 3H2O content of pellets corrected for intercellularspace using Blue Dextran. Cell glycerol was found to accountfor about one-half of the expected osmolarity, the remainderbeing largely accounted for by Na+ and CI. Key words: Dunaliella, isolates, glycerol, ion concentrations 相似文献
19.
ANDERSON W. P; WILLCOCKS D. A.; WRIGHT BARBARA J. 《Journal of experimental botany》1977,28(4):894-901
The ion contents and membrane potentials of the cells of young,hydroponically cultured seedlings of Atriplex hastata L. var.salina, Wallr. have been measured at several different NaClconcentrations. The total tissue concentrations of Na+ and Clincrease as external NaCl increases, but there is always a markedexcess of internal Na+ over Cl; this is balanced by endogenousorganic anion formation with a concomitant extrusion of H+ tothe bathing solution. Membrane potentials of the root cells remain essentially invariantwith changes in external NaCl at approx. 130 mV; thereis no evidence of a radial gradient of potential across theroot. The potential seems to contain a cyanide-sensitive electrogeniccomponent, also invariant with NaCl concentration, of about70 mV, and a diffusion component. The electrogenic componentseems likely to be a H+ efflux, probably through a H+ uniportATPase. 相似文献
20.
Effects of Cations on the Cytoplasmic pH of Chara corallina 总被引:1,自引:0,他引:1
Smith, F. A. and Gibson, J.L. 1985. Effects of cationson the cytoplasmic pH of Chara corallina.J.exp. Bot.36: 13311340 Removal of external Ca2+ from cells of Chara corallina lowersthe cytoplasmic pH, as determined by the intracellular distributionof the weak acid 5,5dimethyloxazolidine2,4dione(DM0), when the external pH is below about 60. This effect isreversed, at least partially, by addition of the following cationsto Ca2+-free solutions: tetraethylammonium (TEA+) and Na+ at5 or 10 mol m-3, Li+ and Cs+ (10 mol m-3), or Mg2+, Mn2+ andLa3+ (02 or 05 mol m-3). Under the same conditions, increasesin pH sometimes, but not always, occur in the presence of 10mol m-3 K+ or Rb+ The results are discussed in relation to the major transportprocesses that determine pH and the electric potential differenceacross the plasma membrane, namely fluxes of H+ and of K+. Thesimplest explanation of the effects of the various cations testedin this study is that they primarily affect pHic via changesin influx of H+ but direct effects on the H+ pump or on K+ fluxesmay also be involved Key words: Chara corallina, cytoplasmic pH, cations, H+transport 相似文献