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1.
Putative morphogen, DIF, of Dictyostelium discoideum induces apoptosis in rat pancreatic AR42J cells
Yuzuru Kubohara Chiharu Kimura Kazuhiko Tatemoto 《Development, growth & differentiation》1995,37(6):711-716
We have recently shown that differentiation-inducing factor-1 (DIF-1) of Dictyostelium discoideum is capable of raising intracellular calcium concentration ([Ca2+ ]i ) and suppressing cell proliferation of rat pancreatic AR42J cells in a dose-dependent manner, and that DIF-1 at a concentration of 40 μmol/L is toxic to the cells. In this study, we have further characterized the cytotoxic effect of DIF-1 on AR42J cells and have analyzed the effect of DIF-1 on [Ca2+ ]i . In the presence of 40 μmol/L DIF-1, cells began to bleb after approximately 6 h, and most had died within 48 h. Biochemical analysis revealed that DNA fragmentation was accompanied by cell death. Monitoring the changes in [Ca2+ ]i induced by DIF-1, it was found that cells were able to adapt to stimulation with DIF-1 so that they did not respond to subsequent stimulation by DIF-1. These results indicate that DIF-1 induced apoptosis in AR42J cells probably via a cell signaling system. 相似文献
2.
Involvement of Calcium Influx in Muscarinic Cholinergic Regulation of Phospholipase C in Cerebellar Granule Cells 总被引:4,自引:0,他引:4
Abstract: Inositol phosphate accumulation on carbachol stimulation of rat cerebellar granule cells shows a marked dependence on factors affecting cytosolic Ca2+ concentration ([Ca2+ ]c ). After 5 min, potassium depolarisation caused a modest accumulation of inositol phosphates but augmented the response to carbachol by a factor of 2–3. These effects of potassium were dependent on an extracellular source of calcium and could be partially blocked by specific (nifedipine) and nonspecific (verapamil) calcium channel blockers. Measurements of [Ca2+ ]c under a range of stimulatory conditions demonstrated a close correlation between the elevation of [Ca2+ ]c and agonist-stimulated phospholipase C (PLC) activity. The maximal potentiation of carbachol-stimulated inositol phosphate accumulation was achieved using 20 m M KCl, which increased [Ca2+ ]c from ∼20 to ∼75 n M , indicating the involvement of relatively low threshold Ca2+ channels and the high sensitivity of the relevant PLC to small changes in [Ca2+ ]c . By contrast, increases in [Ca2+ ]c induced by the Ca2+ ionophore ionomycin were associated with more modest and less potent effects on agonist-stimulated PLC. These results demonstrate a cooperative interaction between a receptor/G protein-regulated PLC and voltage-stimulated elevations of [Ca2+ ]c , which may function to integrate ionotropic and metabotropic signalling mechanisms in cerebellar granule cells. 相似文献
3.
Modulation of Ion Gradients and Glutamate Release in Cultured Cerebellar Granule Cells by Ouabain 总被引:8,自引:0,他引:8
Abstract: Upon addition of the cardiac glycoside ouabain to cultured cerebellar granule cells, an immediate increase in intracellular free sodium is evoked mediated by two pathways, a voltage-sensitive channel blocked by tetrodotoxin and a channel sensitive to flunarizine. Ouabain induces a steady plasma membrane depolarization in low Ca2+ medium; whereas in the presence of Ca2+ , a distinct discontinuity is observed always preceded by a large increase in intracellular free Ca2+ ([Ca2+ ]c ). The plateau component of the increase can be inhibited additively by the L-type Ca2+ channel antagonist nifedipine, the spider toxin Aga-Gl, and the NMDA receptor antagonist MK-801. Single-cell imaging reveals that the [Ca2+ ]c increase occurs asynchronously in the cell population and is not dependent on a critical level of extracellular glutamate or synaptic transmission between the cells. A prolonged release of glutamate is also observed that is predominantly Ca2+ dependent for the first 6–10 min after the evoked increase in [Ca2+ ]c . This release is four times as large as that observed with 50 m M KCl and is predominantly exocytotic because release was inhibited by tetanus toxin, the V-type ATPase inhibitor bafilomycin, and Aga-Gl. It is proposed, therefore, that ouabain induces a period of membrane excitability culminating in a sustained exocytosis above that observed upon permanent depolarization with KCl. 相似文献
4.
Cytoplasmic calcium ion (Ca2+ ) has generally been proposed to be a key factor of numerous cellular processes. Among several agents which might be expected to alter cytoplasmic Ca2+ -concentration ([Ca2+ ]i ), unexpectedly Ca2+ -antagonist TMB-8 was found to raise considerably [Ca2+ ]i , and inhibited not only the formation of prespore cells, but also their maintenance in the monolayer cultures of Dictyostelium discoideum . This seems to indicate that higher [Ca2+ ]i is unfavorable to the prespore differentiation. In this study, we adopted the monolayer culture technique to monitor cell differentiation. However, in high density monolayers there arised a number of unique cells which was highly vacuolated and morphologically intermediate between the stalk and spore cells. These vacuolated cells having both cellulosic wall and spore coat were also induced by differentiation inducing factor (DIF). Thus the monolayer culture system used might be not necessarily qualified to monitor the terminal differentiation of Dictyostelium cells. Nevertheless, the data presented here have strongly suggested that DIF have two physiologically valued roles: 1) Induction of the membrane fusion of vesicles and/or vacuoles (vacuolization), and 2) Induction of the fusion between the cell membrane and vacuole (or vesicle) membrane (exocytosis). 相似文献
5.
Changes in sodium and potassium in Nitellopsis cells treated with transient salt stress 总被引:3,自引:3,他引:0
Abstract. Nitellopsis cells grown in fresh water have a relatively low cytoplasmic Na+ (11 mol m−3 ) and high cytoplasmic K+ (90 mol m−3 ) content. A 30-min treatment with 100 mol m−3 external NaCl resulted in a high [Na+ ]c (90 mol m−3 ) and a low [K+ ]c (33 mol m−3 ), Subsequent addition of external Ca2+ (10 mol m−3 ) prevented Na+ influx and then [Na+ ]c decreased slowly. Changes in [K+ ]c were opposite to [Na+ ]c . During the recovery time vacuolar Na+ increased, while vacuolar K+ decreased. Since all these processes proceeded also under ice-cold conditions, the restoration of original cytoplasmic ion compositions is suggested to be a passive nature. The notion that the passive movement of ions across the tonoplast can act as an effective and economic mechanism of salt tolerance under transient or under mild salt stress conditions is discussed. 相似文献
6.
Yuzuru Kubohara 《FEMS microbiology letters》1995,134(1):15-18
Abstract To clarify the mechanism of stalk cell differentiation in Dictyostelium discoideum (strain NC4), we have examined the effects of Zn2+ on in vitro cell differentiation of prestalk and prespore cells isolated from normally formed slugs. Prestalk cells did not differentiate into stalk cells under submerged conditions, but in the presence of the stalk-inducing factor-1 (DIF-1) at 100 nM or Zn2+ at 5 mM, a small number of the cells (< 15%) differentiated into stalk cells. Interestingly, Zn2+ in combination with DIF-1 induced the prestalk-to-stalk conversion at high efficiencies (approx. 60%). Furthermore, isolated prespore cells were also converted to stalk cells at high efficiencies (approx. 50%) in the presence of both DIF-1 and Zn2+ , while the conversion poorly occurred in the absence of Zn2+ . These results indicate that Zn2+ may mimic some cellular interaction(s) which are required for stalk cell formation in this strain. 相似文献
7.
C. Moyen K. E. Hammond-Kosack J. Jones M. R. Knight & E. Johannes 《Plant, cell & environment》1998,21(11):1101-1111
We show here that, within 1–2 min of application, systemin triggers a transient increase of cytoplasmic free calcium concentration ([Ca2+ ]c ) in cells from Lycopersicon esculentum mesophyll. The systemin-induced Ca2+ increase was slightly but not significantly reduced by L-type Ca2+ channel blockers (nifedipine, verapamil and diltiazem) and the Ca2+ chelator [ethylene glycol tetraacetic acid (EGTA)], whereas inorganic Ca2+ channel blockers (LaCl3 , CdCl2 and GdCl3 ) and compounds affecting the release of intracellular Ca2+ from the vacuole (ruthenium red, LiCl, neomycin) strongly reduced the systemin-induced [Ca2+ ]c increase. By contrast, no inhibitory effect was seen with the potassium and chloride channel blockers tested. Unlike systemin, other inducers of proteinase inhibitor (PI) and of wound-induced protein synthesis, such as jasmonic acid (JA) and bestatin, did not trigger an increase of cytoplasmic Ca2+ . The systemin-induced elevation of cytoplasmic Ca2+ which might be an early step in the systemin signalling pathway, appears to involve an influx of extracellular Ca2+ simultaneously through several types of Ca2+ permeable channels, and a release of Ca2+ from intracellular stores sensitive to blockers of inositol 1,4,5-triphosphate (IP3 )- and cyclic adenasine 5'-diphosphoribose (cADPR)-mediated Ca2+ release. 相似文献
8.
Katsuaki Hoshino Takeshi Shimizu Yutaka Sendai Tatsuo Harumi Norio Suzuki 《Development, growth & differentiation》1992,34(4):403-411
We examined the effects of two egg jelly components, a fucose sulfate glycoconjugate (FSG) and sperm-activating peptide I (SAP-I: Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly), on the intracellular pH (pHi ) and Ca2+ ([Ca2+ ]i ) of spermatozoa of the sea urchin Hemicentrotus pulcherrimus . FSG and/or SAP-I induced elevations of [Ca2+ ]; and pHi in the spermatozoa at pH 8.0. At pH 8.0, a second addition of FSG did not induced further elevation of the [Ca2+ ]i or pHi of spermatozoa treated with FSG, but addition or FSG after SAP-I or of SAP-I after FSG induced further increases of [Ca2+ ]i and pHi , At pH 6.6, FSG and/or SAP-I did not induce significant elevation of the [Ca2+ ]i , although SAP-I elevated the pHi , its half-maximal effective concentration being 10 to 100 pM. At pH 8.0, tetraethyl-ammonium, a voltage-sensitive K+ -channel blocker, inhibited induction of the acrosome reaction and elevations of [Ca2+ ]i and pHi by FSG, but did not affect those by SAP-I. These results suggest that FSG and SAP-I activate different Ca2+ and H+ transport systems. 相似文献
9.
YUKIO FUJINO KEIKO MITSUNAGA IKUO YASUMASU 《Development, growth & differentiation》1987,29(6):591-597
Embryos kept with omeprazole, a specific H+ , K+ -ATPase inhibitor, in a period of development between the mesenchyme blastula and the pluteus corresponding stage became abnormal plutei having quite small spicules, somewhat poor pluteus arms and apparently normal archenterons. In micro-mere-derived cells, kept with omeprazole at pH 8.2 in a period between 15 and 40 hr of culture at 20°C, omeprazole strongly inhibited spicule formation but did not block the outgrowth of pseudopodial cables, in which spicule rods were to be formed. These indicate that omeprazole probably exerts no obvious inhibitory effects other than spicule rods formation. Omeprazole-sensitive H+ , K+ -ATPase, an H+ pump, seems to be indispensable for CaCO3 deposition (formation of spicule rod) in these spicule forming cells. H+ , produced in overall reaction for CaCO3 formation: Ca2+ + CO2 +H2 O°CaCO3 +2H+ , is probably released from the cells by this H+ pump and hence, this reaction tends to go to CaCO3 production to form spicule rods. Omeprazole, known to become effective following its conversion to a specific inhibitor of H+ , K+ -ATPase at acidic pH, is able to inhibit formation of spicule rod at alkaline pH in sea water. This is probably due to an acidification of sea water near the cell surface by H+ ejection in H+ , K+ -ATPase reaction. 相似文献
10.
Abstract: Nitric oxide has been recognized in recent years as an important mediator of neuronal toxicity, which in many cases involves alterations of the cytoplasmic Ca2+ concentration ([Ca2+ ]i ). In [Ca2+ ]i fluorimetric experiments on cultured hippocampal neurons, the nitric oxide-releasing agent S -nitrosocysteine produced a delayed rise in [Ca2+ ]i over a 20-min exposure, which was accompanied by a progressive slowing of the kinetics of recovery from depolarization-induced [Ca2+ ]i transients. These effects were blocked by oxyhemoglobin and by superoxide dismutase, confirming nitric oxide as the responsible agent, and suggesting that they involved peroxynitrite formation. Similar alterations of [Ca2+ ]i homeostasis were produced by the mitochondrial ATP synthase inhibitor oligomycin, and when an ATP-regenerating system was supplied via the patch pipette in combined whole-cell patch-clamp-[Ca2+ ]i fluorimetry experiments, S -nitrosocysteine had no effect on the resting [Ca2+ ]i or on the recovery kinetics of [Ca2+ ]i transients induced by direct depolarization. We conclude that prolonged exposure to nitric oxide disrupts [Ca2+ ]i homeostasis in hippocampal neurons by impairing Ca2+ removal from the cytoplasm, possibly as a result of ATP depletion. The resulting persistent alterations in [Ca2+ ]i may contribute to the delayed neurotoxicity of nitric oxide. 相似文献
11.
Carbon dioxide induces increases in guard cell cytosolic free calcium 总被引:10,自引:0,他引:10
Alex A.R. Webb Martin R. McAinsh Terry A. Mansfield Alistair M. Hetherington 《The Plant journal : for cell and molecular biology》1996,9(3):297-304
The hypothesis that increases in cytosolic free calcium ([Ca2+ ]i ) are a component of the CO2 signal transduction pathway in stomatal guard cells of Commelina communis has been investigated. This hypothesis was tested using fura-2 fluorescence ratio photometry to measure changes in guard cell [Ca2+ ]i in response to challenge with 700 µl l−1 CO2 . Elevated CO2 induced increases in guard cell [Ca2+ ]i which were similar to those previously reported in response to abscisic acid. [Ca2+ ]i returned to resting values following removal of the CO2 and further application of CO2 resulted in a second increase in [Ca2+ ]i . This demonstrated that the CO2 -induced increases in [Ca2+ ]i were stimulus dependent. Removal of extracellular calcium both prevented the CO2 -induced increase in [Ca2+ ]i and inhibited the associated reduction in stomatal aperture. These data suggest that Ca2+ acts as a second messenger in the CO2 signal transduction pathway and that an increase in [Ca2+ ]i may be a requirement for the stomatal response to CO2 . 相似文献
12.
Abstract: The role of the Na+ /Ca2+ exchanger and intracellular nonmitochondrial Ca2+ pool in the regulation of cytosolic free calcium concentration ([Ca2+ ]i ) during catecholamine secretion was investigated. Catecholamine secretion and [Ca2+ ]i were simultaneously monitored in a single chromaffin cell. After high-K+ stimulation, control cells and cells in which the Na+ /Ca2+ exchange activity was inhibited showed similar rates of [Ca2+ ]i elevation. However, the recovery of [Ca2+ ]i to resting levels was slower in the inhibited cells. Inhibition of the exchanger increased the total catecholamine secretion by prolonging the secretion. Inhibition of the Ca2+ pump of the intracellular Ca2+ pool with thapsigargin caused a significant delay in the recovery of [Ca2+ ]i and greatly enhanced the secretory events. These data suggest that both the Na+ /Ca2+ exchanger and the thapsigargin-sensitive Ca2+ pool are important in the regulation of [Ca2+ ]i and, by modulating the time course of secretion, are important in determining the extent of secretion. 相似文献
13.
In embryos of the sea urchin, Hemicentrotus pulcherrimus , as well as in cultured cells derived from isolated micromeres, spicule formation was inhibited by allylisothiocyanate, an inhibitor of H+ , K+ -ATPase, at above 0.5 μM and was almost completely blocked at above 10 μM. Amiloride, an inhibitor of Na+ , H+ antiporter, at above 100 μM exerted only slight inhibitory effect, if any, on spicule formation. Intravesicular acidification, determined using [ dimethylamine -14 C]-aminopyrine as a pH probe, was observed in the presence of ATP and 200 mM KCl in microsome fraction obtained from embryos at the post gastrula stage, at which embryos underwent spicule calcification. Intravesicular acidification and K+ -dependent ATPase activity were almost completely inhibited by allylisothiocyanate at 10 μM. Allylisothiocyanate-sensitive ATPase activity was found mainly in the mesenchyme cells with spicules isolated from prisms. H+ , K+ -ATPase, an H+ pump, probably mediates H+ release to accelerate CaCO3 deposition from Ca2+ , CO2 and H2 O in the primary mesenchyme cells. Intravesicular acidification was stimulated by valinomycin at the late gastrula and the prism stages but not at the pluteus stage. K+ permeability probably increases after the prism stage to activate H+ release. 相似文献
14.
Increases in cytosolic free Ca2+ ([Ca2+ ]cyt ) are common to many stress-activated signalling pathways, including the response to saline environments. We have investigated the nature of NaCl-induced [Ca2+ ]cyt signals in whole Arabidopsis thaliana seedlings using aequorin. We found that NaCl-induced increases in [Ca2+ ]cyt are heterogeneous and mainly restricted to the root. Both the concentration of NaCl and the composition of the solution bathing the root have profound effects on the magnitude and dynamics of NaCl-induced increases in [Ca2+ ]cyt . Alteration of external K+ concentration caused changes in the temporal and spatial pattern of [Ca2+ ]cyt increase, providing evidence for Na+ -induced Ca2+ influx across the plasma membrane. The effects of various pharmacological agents on NaCl-induced increases in [Ca2+ ]cyt indicate that NaCl may induce influx of Ca2+ through both plasma membrane and intracellular Ca2+ -permeable channels. Analysis of spatiotemporal [Ca2+ ]cyt dynamics using photon-counting imaging revealed additional levels of complexity in the [Ca2+ ]cyt signal that may reflect the oscillatory nature of NaCl-induced changes in single cells. 相似文献
15.
Apparent phytotoxicity of mononuclear hydroxy-aluminum to four dicotyledonous species 总被引:3,自引:0,他引:3
It has long been assumed that Al3+ is an important rhizotoxic ion in acid soils around the world, but the toxicity of Al3+ relative to mononuclear hydroxy-Al [AlOH2+ and Al(OH)+ 2 ] has been examined in detail only for an Al-sensitive wheat variety ( Triticum aestivum L. cv. Tyler). That plant appears to be sensitive to Al3+ but not to AlOH2+ and Al(OH)+ 2 . New experiments, and reanalyses of previously published experiments, provide evidence that dicotyledonous species may be sensitive to mononuclear hydroxy-Al and that Al3+ may be nontoxic, or less toxic, to those plants. Despite these consistently measured differences between wheat and the dicotyledons, the determination of relative toxicities (Al3+ vs mononuclear hydroxy-Al) may be an intractable problem. Because of hydrolysis equilibria, (AlOH2+ ) and (Al(OH)+ 2 ) are equivalent to (Al3+ )k1 (H+ )−1 and (l3+ )k2 (H+ )−2 , respectively, in which k1 and k2 are the first and second hydrolysis constants (braces denote activities). Thus, any expression of root elongation as a function of mononuclear hydroxy-Al can be alternatively expressed as a function of (Al3+ ) and (H+ ). Toxicity attributed to mononuclear hydroxy-Al may actually be Al3+ toxicity that increases as pH rises (i.e. Al3+ toxicity ameliorated by H+ ). 相似文献
16.
Tadashi Tojo Yasuyuki Kamata Akiko Fujiwara Ikuo Yasumasu 《Development, growth & differentiation》1995,37(1):49-56
In sea urchin eggs, 10 μg/mL melittin was found to induce fertilization envelope formation without any increase in [Ca2+ ]i (the intracellular free Ca2+ level). On the other hand, 10 μmol/L Br-A23187 and 100 μg/mL SDS induced fertilization envelope formation associated with [Ca2+ ]i increase. If EGTA was injected into eggs to make an intracellular concentration of 2 mmol/L, [Ca2+ ]i became quite low and was not altered by melittin, or by Br-A23187 and SDS. In eggs containing EGTA, fertilization envelope formation was induced by melittin even in Ca2+ -free artificial sea water, but not by Br-A23187 or SDS. Thus [Ca2+ ]i is essential for induction of a fertilization envelope in sea urchin eggs by Br-A23187 or SDS but not by melittin. Melittin probably activates some Ca2+ -independent reaction downstream of Ca2+ -dependent reactions in a sequential reaction system that finally results in fertilization envelope formation. 相似文献
17.
The self-incompatibility response in Papaver rhoeas is mediated by cytosolic free calcium 总被引:6,自引:1,他引:5
Vernonica E. Franklin-Tong Jon P. Ride Nick D. Read Anthony J. Trewavas F. Christopher H. Franklin 《The Plant journal : for cell and molecular biology》1993,4(1):163-177
The role of Ca2+ signalling during the self-incompatibility (SI) response in Papaver rhoeas L. has been investigated using Ca2+ -sensitive dyes. Pollen tubes were micro-injected with Calcium Green-1 and cytosolic free calcium ([Ca2+ ]i ) imaged using laser scanning confocal microscopy (LSCM). Addition of incompatible stigmatic S-glycoproteins induced a transient increase in the level of [Ca2+ ]i in pollen tubes. In contrast, no rise in [Ca2+ ]i was detectable after addition of either compatible or heat-denatured incompatible stigmatic S-glycoproteins. The elevation of [Ca2+ ]i was followed by the specific inhibition of pollen tube growth in incompatible reactions. It has been shown previously that gene expression in pollen tubes is switched on during an incompatible reaction. Since the [Ca2+ ]i transient appeared to originate from the region where the nuclei are located, Ca2+ may be involved in locally regulating the expression of these genes. The photoactivation of caged Ca2+ to artificially elevate [Ca2+ ]i resulted in the inhibition of pollen tube growth and thus mimicked the SI response. Taken together, the results provide an important link between a transient rise in [Ca2+ ]i and the biological phenomenon of inhibition of pollen tube growth and demonstrate, for the first time, direct evidence that the SI response in P. rhoeas is mediated by [Ca2+ ]i . 相似文献
18.
Yasuyuki Kamata Masatoshi Mita Akiko Fujiwara Tadashi Tojo Jiro Takano Akira Ide Ikuo Yasumasu 《Development, growth & differentiation》1997,39(4):419-428
In sea urchin eggs activated by sperm, A23187 or melittin, BPB (4-bromophenacyl bromide, a phospholipase A2 inhibitor) blocked fertilization envelope formation and transient CN− -insensitive respiration in a concentration-dependent manner. BPB had virtually no effect on the increase in [Ca2+ ]i , (cytosolic Ca2+ level), the activity of phosphorylase a and the rate of protein synthesis, as well as acid production and augmentation of CN− -sensitive respiration. BPB also inhibited fertilization envelope formation and augmentation of CN− -insensitive respiration induced by melittin. Melittin, known to be an activator of phospholipase A2 , induced the envelope formation, acid production, augmentation of CN− -insensitive and sensitive respiration, but did not cause any increase in [Ca2+ ]i , the phosphorylase a activity and the rate of protein synthesis. An activation of phospholipase A2 induced by Ca2+ or melittin seems to result in cortical vesicle discharge and production of fatty acids, which are to be utilized in CN− -insensitive lipid peroxidase reactions. Activation of other examined cell functions in eggs activated by sperm or A23187, probably results from Ca2+ -triggered sequential reactions other than Ca2+ -caused activation of phospholipase A2 . 相似文献
19.
Abstract— The present study was undertaken to characterize the cholinergic system of primary cell cultures of mouse and rat CNS.
In confirmation of previous reports, primary cultures were found to contain choline acetyltransferase (ChAc). Furthermore they contain acetylcholine (ACh) as measured by two different bioassays. They also synthesize [3 H]ACh from [3 H]Choline offered to the cultures.
The formation of [3 H]ACh is inhibited in the presence of hemicholinium-3 (10−6 m ) to 50% or ouabain (10−3 m ) to 20% of the values found in untreated cultures. Omission of Na + from the incubation solution also diminishes the [3 H]ACh formation of the cells.
[3 H]ACh is released upon depolarisation by K+ ions in a concentration dependent manner. The release can be prevented by lack of Ca2+ ions in the incubation solution. 相似文献
In confirmation of previous reports, primary cultures were found to contain choline acetyltransferase (ChAc). Furthermore they contain acetylcholine (ACh) as measured by two different bioassays. They also synthesize [
The formation of [
[
20.
As water and nutrient uptake should be related in the response of plants to salinity, the aim of this paper is to establish whether or not aquaporin functionality is related to H+ -ATPase activity in root cells of pepper ( Capsicum annuum L.) plants. Thus, H+ -ATPase activity was measured in plasma membrane vesicles isolated from roots and aquaporin functionality was measured using a cell pressure probe in intact roots. Salinity was applied as 60 m M NaCl or 60 m M KCl, to determine which ion (Na+ , K+ or Cl− ) is producing the effects. We also investigated whether the effects of both salts were ameliorated by Ca2+ . Similar results were obtained for cell hydraulic conductivity, Lpc , and H+ -ATPase activity, large reductions in the presence at NaCl or KCl and an ameliorative effect of Ca2+ . However, fusicoccin (an activator of H+ -ATPase) did not alter osmotic water permeability of protoplasts isolated from roots. Addition of Hg2+ inhibited both ATPase and aquaporins, but ATPase also contains Hg-binding sites. Therefore, the results indicate that H+ -ATPase and aquaporin activities may not be related in pepper plants. 相似文献