盐胁迫下小麦体细胞杂种与亲本小麦幼苗的生长量和Na+、K+含量比较

对小麦体细胞杂种F6株系Ⅰ-1-3和其亲本小麦济南177的幼苗在不同NaC1浓度处理6d时的生长量和Na^ 、K^ 含量进行了比较。结果表明：盐胁迫下杂种的生长量明显高于亲本小麦。随着盐浓度的增加,杂种和亲本的叶、茎和根中Na^ 含量均增加,但杂种叶与茎的Na^ 含量显著低于亲本,而根的却高于亲本,这可能提示杂种根部液泡较亲本有较强的储Na^ 功能。受盐胁迫的杂种叶与茎中K^ 含量显著高于亲本,K^ ／Na^ 比值高。杂种的Na^ 净积累速率也高于亲本。可见杂种比亲本小麦有更强的耐盐性。     

盐胁迫下盐桦生理响应的变化分析

对组织培养获得的盐桦（Belula halophila）苗在盐胁迫下的生理指标和解剖结构进行了分析,结果显示,随着盐浓度的增加,植物叶片相对含水量逐渐降低;脯氨酸（Pro）含量逐渐增加;叶片丙二醛（MDA）含量和过氧化氢酶（CAT）活性大小存在相关性,在50～200mmol／L盐胁迫下,植物的CAT活性是递增的,200mmol／LNaCl处理时达到最高,同时叶片MDA含量在50～200mmol／L盐处理时变化不明显;CAT活性在300mmol／LNaCl处理时突然降低,此时叶片MDA含量大;植物叶片和根的离子含量测定表明,在盐胁迫下K^＋／Na^＋比值逐渐降低,叶片中K^＋含量始终高于Na^＋含量;石蜡切片和扫描电镜发现盐桦茎、叶中有晶体状物质存在,通过X-ray分析表明这种晶体含有C,O,Ca元素,相关的细胞成分化学实验进一步确定其结晶体的成分。     

盐胁迫下氯丙嗪和LaCl3对稻苗K^＋、Na^＋、Cl^—吸收转运的影响

研究了氯丙嗪（CPZ）和LaCl3预处理阻碍Ca^2 。CaM信使系统传导后,盐胁迫下稻苗体内Na^ 、K^ 和Cl^-含量及吸收转运的变化。结果表明：CPZ和LaCl3预处理后,盐胁迫下稻苗对K^ /Na^ 的选择性吸收下降,致使稻苗K^ 含量减少、Na^ 含量增加,Na^ /K^ 比值显著增加;并且稻苗地上部Cl^-含量也显著增加,盐胁迫处理稻苗2d后解除盐胁迫,改用蒸馏水培养,在蒸馏水中加入CPZ或LaCl3时,稻苗中含有较高的Na^ ,即CPZ和LaCl3抑制稻苗将体内Na^ 排出体外的能力,上述结果表明,盐胁迫下,Ca^2 .CaM信使系统可能参与稻苗对K^ 、Na^ 和Cl^-的吸收转运以适应盐胁迫。     

硅改善盐胁迫下库拉索芦荟生长和离子吸收与分布

Si2．0mmol／L处理明显缓解NaCl 100、200mmol／L胁迫120d对库拉索芦荟（Aloevera）生长的抑制作用。Si可显著降低NaCl胁迫下芦荟植株中的Na^＋和Cl^-含量,提高K^＋含量,从而显著降低K^＋／Na^＋,促进根对K^＋的选择性吸收（ASK,Na）和K^＋向地上部的选择性运输（TSK,Na）,以维持植株体内的离子稳态。根系和叶片横切面的X-射线能谱微区分析结果进一步证实了这一结果。Si改善盐胁迫下芦荟对K^＋的选择性吸收和运输的机制之一是通过显著提高盐胁迫下芦荟根细胞质膜H^＋ATPase、液泡膜H^＋-ATPase和液泡膜H^＋-PPase的活性。     

外源硅对盐胁迫下黄瓜幼苗叶绿体活性氧清除系统的影响

以黄瓜为材料,研究了外源硅（K2SiO3 1．0mmol／L）对NaCl（50mmol/L）胁迫下黄瓜幼苗叶绿体中Na^＋、K^＋向叶绿体分配及活性氧清除系统的影响。结果表明：盐胁迫下硅处理使叶绿体在K^＋与Na^＋之间选择性吸收K^＋,从而降低了叶绿体内Na^＋的含量;同时Si处理可以显著降低盐胁迫下叶绿体中过氧化氢（H2O2）和丙二醛（MDA）含量,提高超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）、谷胱甘肽还原酶（GR）和脱氢抗坏血酸还原酶（DHAR）的活性及抗坏血酸（ASA）、还原型谷胱甘肽（GSH）含量。说明Si不仅能降低叶绿体对Na^＋的选择吸收,还能增强叶绿体活性氧清除系统清除活性氧的能力,缓解盐胁迫对叶绿体膜的伤害。     

盐胁迫下水稻叶绿体中Na+、Cl-积累导致叶片净光合速率下降

研究了0-200mmol/L的NaCl胁迫下耐盐性不同的水稻品种Pokkali(耐盐）和Peta(盐敏感）根系,叶片和叶绿体中Na^ ,K^ 和Cl^-含量的变化及其与叶片光合作用的关系。结果表明：随着NaCl胁迫时间和浓度的增加,供试2个品种在根,叶片和叶绿体中Na^ ,Cl^－含量增加,K^ 含量下降。耐盐品种体内Na^ ,Cl^－含量增加或K^ 含量减少的幅度小于盐敏感品种。在200mmol/L的NaCl胁迫下盐敏感品种根,叶片和叶绿体中的Na^ /K^ 分别是耐盐品种的208％,308％和297％。与Na^ 相比,耐盐品种根系对K^ 吸收和向叶片运输的选择性（SK,Na)较强。但在经过0,100和200mmol/L的NaCl处理后2个品种叶绿体中的Na^ /K^ 均高于叶片（SK,Na均小于1）。盐胁迫下水稻叶绿体中Na^ ,Cl^-含量和Na^ /K^ 与叶片净光合速度呈极显著负相关。     

K^＋营养对NaCl胁迫下盐地碱蓬生长及叶片液泡膜V—H^＋—ATP和V—H^＋—PPase活性的影响

对溶液培养的盐地碱蓬（Suaeda salsa L.)幼苗进行不同浓度NaCl胁迫并改变培养液中K^ 浓度,以了解K^ 营养对NaCl胁迫下盐地碱蓬幼苗生长及叶片液泡膜V－H^ -ATPase、V－H^ -PPase活性的影响。提高培养液K^ 浓度可明显增加盐胁迫下碱蓬植株的鲜重、干重,促进盐地碱蓬叶片及根部组织K^ 积累。盐地碱蓬叶片液泡膜V－H^ -ATPase至少由A、B、C、D、E及c亚基组成,其表达量在缺K^ 处理（12μmol/L K^ )下随盐胁迫浓度的增加而减小,而在正常K^ （6mmol/L)培养下则随盐胁迫浓度的增加而增加;盐地碱蓬叶片液泡膜V－H^ -PPase分子量为72kD,在缺K^ 和正常K^ 供应情况下,V－H^ -PPase均有较高表达。V－H^ -ATPase及V－H^ -PPase活性变化与其亚基表达量变化基本成正相关。结果表明：K^ 对盐生植物碱蓬的耐盐性有重要作用,盐胁迫下,K^ 可能参与了V－H^ -ATPase和V－H^ -PPase活性调控。     

甘氨酸甜菜碱增强青菜抗盐的作用

通过对青菜（Brassica chinensis L.)叶面喷施甜菜碱,发现其易于为叶片所吸收并运至其他部位,一定浓度范围内的甜菜碱可明显增强青菜对盐胁迫的抗性,甜菜碱可显降低盐胁迫下叶和根中Na^ 的累积,这种降低主要是根系对Na^ ,K^ 的选择性吸收能力增强所致,盐胁迫下甜菜碱导致根系质膜H^ -ATPase活性提高了45.1%,据此推测甜菜碱降低植株中Na^ 累积很可能部分由于促进根系质膜的主动排Na^ 过程,另外,甜菜碱对抗盐性的增强还体现有对叶片质膜和叶绿素的稳定作用和对脯氨酸合成的促进。     

土壤盐碱胁迫对春小麦K^＋、Na^＋选择性吸收的影响

通过对2种浓度土壤盐分胁迫下春小麦各品种不同时期各器官K^ 、Na^ 含量以及K^ /Na^ 的变化及其与抗盐性的关系研究,结果表明,随土壤盐浓度的升高,各品种的产量及各农艺性状值均有所下降,但不同品种的下降程度不同。随土壤盐浓度的升高,植株中K^ 、Na^ 含量均有所增加,但K^ 增加的幅度小于Na^ 的增加幅度,因而K^ /Na^ 呈明显下降趋势;在不同土壤盐分胁迫下,小麦品种K^ 、Na^ 随生育进程在体内各器官的分配发生动态变化,在分蘖期地上部K^ /Na^ ＞根部,孕穗期各器官K^ /Na^ 依次为：幼穗＞旗叶＞茎＞倒4叶,而灌浆期则依次为：籽粒＞旗叶＞茎＞倒4叶,说明生长旺盛的器官拒Na^ 能力强于其它器官;不同品种的K^ 、Na^ 含量及K^ /Na^ 不同,一般抗盐性强的品种在各时期均具有较高的K^ /Na^ ,反之则K^ /Na^ 较低;小麦的籽粒产量在一定范围内与其植株地上部各器官的K^ /Na^ 中一定的正相关,其中与分蘖期植株地上部的K^ /Na^ 及叶（K^ /Na^ ）／根（K^ /Na^ ）呈极显著正相关,而与此时期的SNa^ K^ 相关性最强,γ为－0．9670。因而,以分蘖期的K^ /Na^ 尤其是SNa^ K^ 作为小麦田间抗盐性的指标,具有一定的可靠性。     

Na+和Ca2+对拟南芥根原生质体质膜内向K+通道电流的影响

以拟南芥(Arabidopsis thaliana Columbia)根为材料,利用膜片钳技术测定其根细胞原生质体质膜内向K^ 电流,并对Na^ 对其K^ 电流的影响进行了初步研究,发现Na^2 可明显抑制拟南芥根细胞原生质体的内向K^ 电流,外施Ca^2 可缓解Na^ 对内向K^ 电流的抑制．说明Ca^2 参与了质膜上K^ 通道对K^ ／Na^ 的选择性吸收的调节,从而使植物适应盐胁迫．     

常夏石竹耐盐突变体渗透调节的研究

在离体培养条件下利用γ-射线作诱变剂获得耐0.5%、0.7%、1.0%NaCl的突变系,通过对稳定突变系植株叶片渗透剂含量及对渗透势贡献大小的测定表明耐盐突变体叶中K+、游离氨基酸、Na+、脯氨酸的含量高于对照,其中脯氨酸和Na+积累最明显。而叶片中可溶性糖的含量、K+/Na+低于对照。Na+对突变体植株叶片渗透势贡献最大,是最主要的渗透调节剂之一。耐盐突变体植株内存在渗透物质的再分配,叶内有吸钾排钠现象。     

Concanavalin A induced changes of lymphocyte p-nitrophenylphosphatase (author's transl)]

The effect of K+, Na+, Mg2+ and ATP on the p-nitrophenylphosphatase activity was investigated. As an enzyme preparation a microsomal fraction of sheep lymphocytes was used. Low concentrations of Mg2+, K+ and Na+ increased, whereas high concentrations decreased the enzyme activity. There was an inhibition of activity by ATP without Na+ in the incubation medium and an increase of enzyme activity at low K:Na-ratio. By concanavalin A in a concentration of 15 mug/ml the p-nitrophenylphosphatase activity was increased in intact cells and the microsomal fraction for 30-40%. The activation was not Na+, K+, Mg2+, p-nitrophenylphosphate or ATP dependent.     

Effects of Systemic Kainic Acid Administration on Regional Na+, K+-ATPase Activity in Rat Brain

Changes in the activity of Na+,K+-ATPase and in the water, Na+, and K+ levels in the parietal cortex, hippocampus, and thalamus were investigated in rats 1, 3, 6, and 24 h following systemic kainic acid injection. An increase in Na+,K+-ATPase activity was observed in all three regions 3 h after the treatment, with a subsequent decrease in enzyme activity. The elevation in Na+,K+-ATPase activity was accompanied by an increase in the Na+ content and a decrease in the K+ content. These changes are presumed to occur because of repeated discharges and excessive prolonged depolarization in response to kainic acid. The decreases in Na+,K+-ATPase activity 6 and 24 h following kainic acid treatment coincide with neuropathological damage and edema formation, mainly in the hippocampus and thalamus.     

The occurrence of thermotolerance in non-proliferating rat hepatocytes in primary culture

The occurrence of thermotolerance, induced by an initial heat treatment at 42 degrees C for 30 min, was studied in adult non-proliferating rat hepatocytes in primary culture. Heat treatment at 42 degrees C for 30 min did not affect cell morphology, cell attachment, Na+, K+ pump activity, K+ content and lactate dehydrogenase accumulation into the medium. In contrast, after exposure to 44 degrees C for 30 min a dramatic change in all these parameters was observed. However, of the cells, which remained attached to the substratum 24 h after treatment, Na+, K+ pump activity and K+ content appeared to be normal compared with untreated cells. Cells, pre-treated at 42 degrees C for 30 min, followed by incubation at 37 degrees C for 16 h, were found to be completely thermal resistant against heat treatment at 44 degrees C, as judged by cell morphology, detachment from the substratum, lactate dehydrogenase accumulation, Na+, K+ pump activity and K+ content. These results show that induction and development of thermotolerance can be studied in non-proliferating cells in primary culture.     

Purification of Na+,K+-ATPase expressed in Pichia pastoris reveals an essential role of phospholipid-protein interactions

Na+,K+-ATPase (porcine alpha/his10-beta) has been expressed in Pichia Pastoris, solubilized in n-dodecyl-beta-maltoside and purified to 70-80% purity by nickel-nitrilotriacetic acid chromatography combined with size exclusion chromatography. The recombinant protein is inactive if the purification is done without added phospholipids. The neutral phospholipid, dioleoylphosphatidylcholine, preserves Na+,K+-ATPase activity of protein prepared in a Na+-containing medium, but activity is lost in a K+-containing medium. By contrast, the acid phospholipid, dioleoylphosphatidylserine, preserves activity in either Na+- or K+-containing media. In optimal conditions activity is preserved for about 2 weeks at 0 degrees C. Both recombinant Na+,K+-ATPase and native pig kidney Na+,K+-ATPase, dissolved in n-dodecyl-beta-maltoside, appear to be mainly stable monomers (alpha/beta) as judged by size exclusion chromatography and sedimentation velocity. Na+,K+-ATPase activities at 37 degrees C of the size exclusion chromatography-purified recombinant and renal Na+,K+-ATPase are comparable but are lower than that of membrane-bound renal Na+,K+-ATPase. The beta subunit is expressed in Pichia Pastoris as two lightly glycosylated polypeptides and is quantitatively deglycosylated by endoglycosidase-H at 0 degrees C, to a single polypeptide. Deglycosylation inactivates Na+,K+-ATPase prepared with dioleoylphosphatidylcholine, whereas dioleoylphosphatidylserine protects after deglycosylation, and Na+,K+-ATPase activity is preserved. This work demonstrates an essential role of phospholipid interactions with Na+,K+-ATPase, including a direct interaction of dioleoylphosphatidylserine, and possibly another interaction of either the neutral or acid phospholipid. Additional lipid effects are likely. A role for the beta subunit in stabilizing conformations of Na+,K+-ATPase (or H+,K+-ATPase) with occluded K+ ions can also be inferred. Purified recombinant Na+,K+-ATPase could become an important experimental tool for various purposes, including, hopefully, structural work.     

Inactivation of Na+, K+ -ATPase from cattle brain by sodium fluoride

The influence of the physiological ligands and modifiers on the plasma membrane Na+, K+ -ATPase from calf brain inactivation by sodium fluoride (NaF) is studied. ATP-hydrolyzing activity of the enzyme was found to be more stable as to NaF inhibition than its K+ -pNPPase activity. The activatory ions of Na+, K+ -ATPase have different effects on the process of the enzyme inhibition by NaF. K+ intensifies inhibition, but Na+ does not affect it. An increase of [Mg2+free] in the incubation medium (from 0.5 to 3.0 mM) rises the sensitivity of Na+, K+ -ATPase to NaF inhibition. But an increase of [ATP] from 0.3 to 1.5 mM has no effect on this process. Ca and Mg ions modify Na+, K+ -ATPase inhibition by fluoride differently. Ca2+free levels this process, and Mg2+free on the contrary increases it. In the presence of Ca ions and in the neutral-alkaline medium (pH 7.0-8.5) the recovery of activity of the transport ATPase inhibited by-NaF takes place. Sodium citrate also protects both ATP-hydrolizing and K-pNPPase activity of the Na+, K+ -ATPase from NaF inhibition. Under the modifing membranous effects (the treatment of plasma membranes by Ds-Na and digitonin) the partial loss of Na+, K+ -ATPase sensitivity to NaF inhibition is observed. It is concluded that Na+, K+ -ATPase inactivation by NaF depends on the influence of the physiological ligands and modifiers as well as on the integrity of membrane structure.     

Evidence for a role of Na+,K(+)-ATPase in the hydration of Atlantic croaker and spotted seatrout oocytes during final maturation.

During final maturation the oocytes of many marine teleosts swell four to five times their original size due to uptake of water. The involvement of active inorganic ion transport and Na+,K(+)-ATPase in oocyte hydration in Atlantic croaker (Micropogonias undulatus) and spotted seatrout (Cynoscion nebulosus), marine teleosts which spawn pelagic eggs, was investigated by examining changes in the inorganic ion content of ovarian follicles containing mainly oocytes, by performing in vitro incubations of the follicles with ion channel blockers, and by assaying membrane preparations of ovaries containing hydrating and non-hydrating oocytes for Na+,K(+)-ATPase activity and content. There were marked increases in the contents of K+, Mg++, and Ca++, but not Na+, in oocytes of M. undulatus and C. nebulosus during hydration. Incubation of follicle-enclosed oocytes in K(+)-free medium or with ouabain or amiloride, inhibitors of Na+,K(+)-ATPase and Na+ channels, respectively, blocked gonadotropin-induced oocyte hydration in M. undulatus. In addition, Na+,K(+)-ATPase activity increased threefold and the concentration of the enzyme increased 50% in ovarian tissue during oocyte hydration. These results strongly suggest a major role for active ion regulation by a ouabain-sensitive Na+,K(+)-ATPase system in oocyte hydration in two species of sciaenid fishes.     

Regulation of acetylated tubulin/Na+,K+-ATPase interaction by L-glutamate in non-neural cells: involvement of microtubules

A subpopulation of membrane tubulin consisting mainly of the acetylated isotype is associated with Na+,K+-ATPase and inhibits the enzyme activity. We found recently that treatment of cultured astrocytes with L-glutamate induces dissociation of the acetylated tubulin/Na+,K+-ATPase complex, resulting in increased enzyme activity. We now report occurrence of this phenomenon in non-neural cells. As in the case of astrocytes, the effect of L-glutamate is mediated by its transporters and not by specific receptors. In COS cells, the effect of L-glutamate was reversed by its elimination from culture medium, provided that d-glucose was present. The effect of L-glutamate was not observed when Na+ was replaced by K+ in the incubation medium. The ionophore monensin, in the presence of Na+, had the same effect as L-glutamate. Treatment of cells with taxol prevented the dissociating effect of L-glutamate or monensin. Nocodazole treatment of intact cells or isolated membranes dissociated the acetylated tubulin/Na+,K+-ATPase complex. The dissociating effect of nocodazol does not require Na+. These results indicate a close functional relationship among Na+,K+-ATPase, microtubules, and L-glutamate transporters, and a possible role in cell signaling pathways.     

Volume-dependent regulation of ion carriers in human and rat erythrocytes: role of cytoskeleton and protein phosphorylation

This study examines the effect of heat-induced cytoskeleton transitions and phosphoprotein phosphatase inhibitors on the activity of shrinkage-induced Na+, K+, 2Cl- cotransport and Na+/H+ exchange in rat erythrocytes and swelling-induced K+, Cl- cotransport in human and rat blood cells. Preincubation of human and rat erythrocytes at 49 degrees C drastically activated K+, Cl- cotransport and completely (rat) or partly (human) abolished its volume-dependent regulation. The same procedure did not affect basal activity of Na+, K+, 2Cl- cotransport but completely abolished its activation by shrinkage thus suggesting the involvement of a thermosensitive element of cytoskeleton network in the volume-dependent regulation of cotransporters. Both the shrinkage- and electrochemical proton gradient-induced Na+/H+ exchange was inhibited by the heat treatment to the same extent (50-70%), thus indicating the different signaling pathways involved in the activation of Na+, K+, 2Cl- cotransport and Na+/H+ exchange by cell shrinkage. This suggestion is in accordance with data on the different kinetics of volume-dependent activation and inactivation of these carriers as well as on their sensitivity to medium osmolality. Both swelling- and heat-induced increments of K+, Cl- cotransport activity were diminished by inhibitors of phosphoprotein phosphatases (okadaic acid and calyculin). In rat erythrocytes these compounds potentiate shrinkage-induced Na+/H+ exchange. On the contrary, neither basal nor shrinkage-induced Na+, K+, 2Cl- cotransport was affected by these compounds. Our results indicate a key role of cytoskeleton network in volume-dependent activation of K+, Cl- and Na+, K+, 2Cl- cotransport and the involvement of protein phosphorylation-dephosphorylation cycle in regulation of the activity of K+, Cl- cotransport and Na+/H+ exchange.     

Effect of heavy metal cations on the activity of membrane Na+, K+ -ATPase in embryos of loach (Misgurnus fossilis L.)

The activity of membrane Na+, K+ -ATPase of embryos of loach (Misgurnus fossilis L.) at early stages of development in the normal conditions and under the influence of heavy metal cations has been investigated. It was established, that the influence of such heavy metal cations as Ni2+, Co2+, Sn2+, Zn2+, Mn2+ and Cd2+ in concentrations 10(-6) - 10(-4) M results in reduction of activity of membrane Na+, K+ -ATPase of loach embryos. It was shown, that the inhibition effect is more expressed with the increase of concentrations of heavy metal cations in the incubation medium. The definition of inhibition constants Io.5 has allowed to analyze the sensitivity of Na+, K+ -ATPase to influence of various cations of heavy metals at different stages of blastomer division. Possible mechanisms of influence of heavy metal cations on the activity of membrane Na+, K+ -ATPase of loach embryos have been considered.