不同季节荷斯坦牛3个微卫星座位与GSH-Px、SOD和Na+/K+-ATP酶活性及日产奶量的关系

选择分别与谷胱甘肽过氧化物酶(GSH-Px)、超氧化物歧化酶(SOD)和Na⁺/K⁺-ATP酶基因紧密连锁的3个微卫星座位BMS2258、SOD1和BM723, 采用PCR及非变性聚丙烯酰胺凝胶电泳分析其在130头荷斯坦牛中的遗传变异, 计算了3个微卫星座位的多态信息含量、有效等位基因数和遗传杂合度, 并利用最小二乘法拟合线性模型初步探索了它们与荷斯坦牛夏、秋季GSH-Px、SOD、Na⁺/K⁺-ATP酶活性及日产奶量的关系。结果表明, 3个微卫星座位与其紧密连锁基因的酶活性及日产奶量均存在显著相关(P<0.05)。BMS2258座位182 bp/164 bp的GSH-Px活性和日产奶量对应的最小二乘均值较高; SOD1座位148 bp/146 bp对应的SOD活性的最小二乘均值较高, 148 bp/148 bp对应的日产奶量最小二乘均值较高; BMS2258座位161 bp/111 bp对应的Na⁺/K⁺-ATP酶活性和日产奶量的最小二乘均值较高, 它们是各自座位上的最有利基因型。     

Na+/H+逆向转运蛋白和植物耐盐性

Na⁺H⁺逆向转运蛋白对植物耐盐起着重要作用 ,它利用质膜H⁺ATPase或液泡膜H⁺ATPase及Ppiase泵H+产生的驱动力把Na⁺排出细胞或在液泡中区隔化以消除Na⁺的毒害。主要讨论植物中Na⁺H⁺逆向转运蛋白研究在分子水平的最新进展.     

西伯利亚白刺质膜Na+/H+逆向转运蛋白基因NsSOS1的分离及表达分析

采用同源克隆技术分离了西伯利亚白刺(Nitraria sibirica)质膜Na~+/H~+逆向转运蛋白基因NsSOS1,并对其在不同胁迫条件下的表达特性进行了分析。NsSOS1包含3 516bp开放阅读框(ORF),编码1 171个氨基酸,蛋白分子量为128.34kD。生物信息学分析显示,NsSOS1包含12个跨膜结构域,具有植物SOS1蛋白的保守结构域。系统发育分析表明,NsSOS1与其他植物质膜Na~+/H~+逆向转运蛋白处于同一个次级分化群,与锦葵科海滨锦葵KvSOS1亲缘关系较近。实时荧光定量RT-PCR分析显示,NsSOS1基因在西伯利亚白刺的根和叶中表达量较高;其表达受到非生物胁迫(NaCl、低温、干旱)和外源激素(MeJA和GA)的诱导,表明NsSOS1基因在西伯利亚白刺抵御逆境胁迫过程中发挥重要作用。     

大鼠前脂细胞质膜Na+/H+交换同时参与细胞的增殖和分化

以原代培养的大鼠前脂细胞为模型 ,以 2′ ,7′ bis ( 2 carboxyethyl) 5 ( 6 ) carboxyfluorescein (BCECF)作为检测胞内pH(pHi)的荧光探针 ,测定不同生长因子刺激下胞内pH的变化 ,证明大鼠肾周前脂细胞质膜存在Na⁺/H⁺交换活性 ,胎牛血清(FCS)能快速激活Na⁺/H⁺交换 ,导致pHi升高 (约 0 .2pH单位 ) ,并引起DNA合成 .Ethyl isopropyl amiloride (EIPA)抑制Na⁺/H⁺交换与DNA合成 .在无血清条件下 ,胰岛素不刺激DNA合成但引起细胞分化 ,表现为胞内脂滴积累和 3 磷酸 甘油脱氢酶(G₃ PDH酶 )活性增强 ,同时激活Na⁺/H⁺交换活性导致pHi升高 ;EIPA既抑制胰岛素对Na⁺/H⁺交换的激活 ,也抑制G₃ PDH酶活性增强 .结果证明 :Na⁺/H⁺交换的激活不仅与大鼠前脂细胞增殖相关 ,同时也是细胞分化的早期事件 .     

川楝素对K+、Ca2+通道活动及细胞内Ca2+浓度的调控

川楝素是我国学者从驱蛔中药中分离、鉴定的一个三萜化合物,已证明具选择地影响神经递质释放,有效地对抗肉毒中毒,促进细胞分化、凋亡,抑制肿瘤增殖,抑制昆虫发育和取食,影响K⁺、Ca²⁺通道活动等多种生物效应. 综述了证明川楝素抑制多种K⁺通道,选择地易化L型Ca²⁺通道和进而升高胞内Ca⁺浓度的研究资料,并对川楝素产生这些生物效应的机制进行了讨论.     

NaHCO3胁迫下3种灌木Na+、K+、Ca2+的吸收及转运

通过盆栽试验,采用原子吸收分光光度法和非损伤微测技术,研究了NaHCO₃胁迫(300 mmol·L^-1)对大洋洲滨藜、四翅滨藜和宁夏枸杞3种灌木离子吸收及运转的影响.结果表明: 随着NaHCO₃浓度升高,两种滨藜和宁夏枸杞叶片中Na⁺含量升高,300 mmol·L^-1NaHCO₃胁迫下,宁夏枸杞叶肉细胞Na⁺的外排增加,两种滨藜净Na⁺外排降低;随着胁迫时间的延长,大洋洲滨藜和宁夏枸杞叶片的K⁺含量下降,Na⁺/K⁺升高,四翅滨藜叶片K⁺含量升高,Na⁺/K⁺降低;随着浓度的升高,宁夏枸杞叶片积累Ca²⁺减少,Na⁺/Ca²⁺高于对照,叶肉细胞Ca²⁺外排;两种滨藜叶Ca²⁺含量总体呈升高趋势,叶肉细胞Ca²⁺表现为内流.在NaHCO₃胁迫下,3种灌木通过不同的策略来消除Na⁺毒害.宁夏枸杞叶片Na⁺的积累抑制了对Ca²⁺的吸收;两种滨藜Ca²⁺的内流促使细胞质中游离Ca²⁺增加,增加的细胞质[Ca²⁺]cyt防治质膜H⁺ ATPase去极化,限制K⁺的外排,从而维持细胞内Na⁺/K⁺的平衡,其中四翅滨藜调控Na⁺/K⁺平衡的能力较强.     

长叶红砂液泡膜Na+/H+逆向转运蛋白基因的克隆及表达特性

为研究长叶红砂(Reaumuria trigyna)离子转运分子机制,利用RT-PCR和RACE技术,克隆到其液泡膜Na+/H+逆向转运蛋白基因(NHX1)的全长cDNA片段,命名为RtNHX1(NCBI序列号为KR919802)。结果表明:RtNHX1的cDNA片段全长2 622bp,开放阅读框1 662bp,5′非编码区509bp,3′非编码区451bp,编码553个氨基酸,推测分子量为60.91kD。该蛋白含有12个跨膜结构域,为疏水蛋白,与其他植物液泡膜Na+/H+逆向转运蛋白NHX1的亲缘关系较近。实时荧光定量PCR对其在NaCl胁迫下的表达检测显示,不同时间和不同浓度NaCl胁迫下,RtNHX1表达量变化均呈先升高后降低趋势,在100mmol/L NaCl胁迫6h和200mmol/L NaCl胁迫后达到最高,表达量分别超过或约是对照的3倍,一定程度反应出RtNHX1参与长叶红砂的盐胁迫应答,是该植物离子转运体系的重要元件。     

Na+吸收对干旱导致的棉花叶片光合系统损伤的缓解作用

以盆栽棉花为材料,在植株高约20 cm时用不同浓度Na Cl溶液浇透后进行持续干旱处理。在干旱处理期间测定叶片叶绿素荧光参数、光合气体交换参数的变化以及植株水分状况和Na+含量,以分析土壤Na Cl施入引起的棉花Na+吸收和积累量的增加对干旱胁迫导致的叶片光合系统损伤的缓解作用及可能原因。结果表明,未用Na Cl处理的棉花植株,其叶片净光合速率随着干旱的延续而持续下降、光合机构在干旱处理后期出现了严重损伤;而Na Cl处理的棉花植株,其叶片净光合速率下降幅度明显小于未用Na Cl处理的,光合机构受损伤程度也较轻或无明显损伤。对各处理棉花植株Na+的吸收和水分状况的测定分析表明,Na Cl处理的植株,其叶片Na+积累显著增加、渗透势降低,细胞膨压显著高于未用Na Cl处理的植株。由此可见,在土壤浇灌Na Cl溶液后的持续干旱条件下,棉花植株吸收和积累Na+增加,降低了组织渗透势、维持了一定的细胞膨压,从而有效缓解了干旱胁迫对叶片光合机构的损伤。     

莳萝蒿适应盐渍环境的Na+区域化方式和生理特征

莳萝蒿是广泛分布在我国北方的一种特殊类型的菊科盐生植物,阐明莳萝蒿特殊的耐盐机制和生理特征有助于丰富植物抗盐性研究的内容。用0、100、200、300、400 mmol/L Na Cl处理莳萝蒿7 d后,比较莳萝蒿盐处理植株与对照植株在生长和生理方面的差异,并详细分析了Na+在莳萝蒿体内的积累水平和区域化方式。结果显示:莳萝蒿虽然能够耐受400 mmol/L Na Cl,但盐处理显著抑制了莳萝蒿的生长,整株鲜重随着盐处理浓度的升高逐渐减小。在水分生理方面,随着盐处理浓度的升高,莳萝蒿叶片细胞的渗透调节能力逐渐增强,其叶片肉质化程度却呈逐渐降低的趋势。分析盐处理对光合作用的影响发现,盐处理后莳萝蒿叶片光合速率与气孔导度显著下降,而其PSⅡ光化学活性并未受到抑制,叶绿素含量甚至逐渐增大,说明盐处理后莳萝蒿叶片光合速率的降低主要是由于气孔因素造成的,而不是由于光合结构被破坏。莳萝蒿体内的Na+含量随着盐处理浓度的升高显著增加,400 mmol/L Na Cl条件下叶、茎、根中的Na+含量分别高达321.4、242.1和182.3μmol/g鲜重;莳萝蒿体内的Na+70%以上积累在叶片内,而叶片内98%左右的Na+积累在叶片原生质体中,叶片原生质体中的Na+平均浓度是质外体1.2—1.8倍,推测其叶片细胞内存在着有效的Na+区域化机制。盐处理后莳萝蒿叶片液泡膜V-H+-ATPase的质子泵活性比对照增加了30%—50%,液泡膜Na+/H+逆向转运活性则增加至对照的4—7倍,进一步证实莳萝蒿叶片具有较强的液泡Na+区域化能力。随着盐处理浓度的升高,Na+在叶片中的分布比例相对减少,V-H+-ATPase的质子泵活性和Na+/H+逆向转运活性增幅也减缓。这种Na+区域化能力使莳萝蒿获得了较强的耐盐性,有效保护了其光系统,降低了细胞汁液渗透势。但是盐处理后这种耐盐方式并不能阻止莳萝蒿叶片肉质化程度和光合活性下降,莳萝蒿生长仍然受盐抑制,说明Na+区域化是莳萝蒿适应盐渍环境的必要条件而非充分条件。     

NaCl胁迫对4种豆科树种幼苗生长和K+、Na+含量的影响

以合欢、刺槐、国槐和皂荚4种豆科树种盆栽实生幼苗为试验材料,研究了NaCl胁迫下4个树种幼苗的生长、耐盐临界浓度和Na⁺、K⁺含量的变化,并对其耐盐性进行了比较.结果表明：NaCl胁迫抑制了4个树种幼苗的生长,苗木的干物质积累量减小、根冠比增大,尤其对合欢和皂荚的影响较大;以相对干质量降至对照组50%时的NaCl浓度作为生长临界NaCl浓度(C₅₀)指标,4个树种的耐盐强弱顺序为：刺槐(5.0‰)＞国槐(4.5‰)＞皂荚(3.9‰)＞合欢(3.0‰);随NaCl浓度的增加,各树种幼苗根、茎、叶中Na⁺含量逐渐增加,K⁺含量先增加后减小（合欢根除外）,而K⁺/Na⁺差异较大.相同浓度NaCl胁迫下,幼苗器官的Na⁺分布为根＞茎＞叶,K⁺因树种和NaCl浓度不同而各异,以叶片中较多,K⁺/Na⁺为叶＞茎＞根.NaCl胁迫下,刺槐的K⁺含量和K⁺/Na⁺较高,地上部分Na⁺含量较低,幼苗干物质量大,耐盐性较强;而合欢的K⁺/Na⁺较小,高浓度NaCl胁迫下地上部分的Na⁺含量较高,幼苗干物质量小,耐盐性较差.苗木地上部分对K⁺的积累和根部对Na⁺的滞留是影响豆科树种耐盐性能的主要因素.     

Mechanisms of liquid flux across pulmonary alveolar epithelial cell monolayers

Summary Active transport of sodium by pulmonary alveolar epithelial cells (AEC) is believed to be an important component of edema clearance in the normal and injured lung. Data supporting this premise have come from measurements of sodium movement across AEC monolayers or from perfused lung model systems. However, direct measurement of fluid flux across AEC monolayers has not been reported. In the present work, AEC were studied with an experimental system for the measurement of fluid flux (Jv) across functionally intact cell monolayers. Primary adult rat type II alveolar epithelial cells were cultured on 0.8 μm nuleopore filters previously coated with gelatin and fibronectin. Intact monolayers were verified by high electrical resistance (> 1000 Θ) at 4–5 d of primary culture. At the same time interval, transmission electron microscopy revealed cells with type I cell-like morphology throughout the monolayer. These were characterized by both adherens and tight junctional attachments. Fluid flux across the monolayers was measured volumetrically over a period of 2 h in the presence of HEPES-buffered DMEM containing 3% fatty acid-free bovine serum albumin. Flux (Jv) was inhibited 39% by 1 × 10⁻⁴ M ouabain (P < 0.01) and 27% by 5 × 10⁻⁴ M amiloride (P < 0.05). These data support the concept that AEC Na⁺/K⁺-ATPase and Na⁺ transport systems are important determinants of AEC transepithelial fluid movement in vitro.     

Role of the furosemide-sensitive Na+/K+ transport system in determining the steady-state Na+ and K+ content and volume of human erythrocytesin vitro andin vivo

Summary To study the physiological role of the bidirectionally operating, furosemide-sensitive Na⁺/K⁺ transport system of human erythrocytes, the effect of furosemide on red cell cation and hemoglobin content was determined in cells incubated for 24 hr with ouabain in 145mm NaCl media containing 0 to 10mm K⁺ or Rb⁺. In pure Na⁺ media, furosemide accelerated cell Na⁺ gain and retarded cellular K⁺ loss. External K⁺ (5mm) had an effect similar to furosemide and markedly reduced the action of the drug on cellular cation content. External Rb⁺ accelerated the Na⁺ gain like K⁺, but did not affect the K⁺ retention induced by furosemide. The data are interpreted to indicate that the furosemide-sensitive Na⁺/K⁺ transport system of human erythrocytes mediates an equimolar extrusion of Na⁺ and K⁺ in Na⁺ media (Na⁺/K⁺ cotransport), a 1:1 K⁺/K⁺ (K⁺/Rb⁺) and Na⁺/Na⁺ exchange progressively appearing upon increasing external K⁺ (Rb⁺) concentrations to 5mm. The effect of furosemide (or external K⁺/Rb⁺) on cation contents was associated with a prevention of the cell shrinkage seen in pure Na⁺ media, or with a cell swelling, indicating that the furosemide-sensitive Na⁺/K⁺ transport system is involved in the control of cell volume of human erythrocytes. The action of furosemide on cellular volume and cation content tended to disappear at 5mm external K⁺ or Rb⁺. Thein vivo red cell K⁺ content was negatively correlated to the rate of furosemide-sensitive K⁺ (Rb⁺) uptake, and a positive correlation was seen between mean cellular hemoglobin content and furosemide-sensitive transport activity. The transport system possibly functions as a K⁺ and waterextruding mechanism under physiological conditiosin vivo. The red cell Na⁺ content showed no correlation to the activity of the furosemide-sensitive transport system.     

Activity of Ion Transporters and Salt Tolerance in Barley

The authors attempted to relate the cultivar-specific salt tolerance in barley (Hordeum distichum L.) to the efficiency of ion transporters in the plasmalemma and tonoplast. The study involved plasmalemma and tonoplast membrane vesicles isolated from roots and leaves of the 7-day-old barley seedlings exposed to elevated NaCl concentrations. Two barley cultivars were employed: salt-tolerant cv. Elo and salt-susceptible cv. Belogorskii. The vesicles were used to measure the transport activity of plasmalemma and tonoplast proton pumps and the cation/anion exchange. The data obtained in the experiments demonstrated that the changes in the activity of ion transporters under salt stress conditions correlated with the barley cultivar-specific tolerance to elevated NaCl concentrations.     

Regulation of the Na+/K+-ATPase by insulin: Why and how?

The sodium-potassium ATPase (Na⁺/K⁺-ATPase or Na⁺/K⁺-pump) is an enzyme present at the surface of all eukaryotic cells, which actively extrudes Na⁺ from cells in exchange for K⁺ at a ratio of 3:2, respectively. Its activity also provides the driving force for secondary active transport of solutes such as amino acids, phosphate, vitamins and, in epithelial cells, glucose. The enzyme consists of two subunits ( and ) each expressed in several isoforms. Many hormones regulate Na⁺/K⁺ -ATPase activity and in this review we will focus on the effects of insulin. The possible mechanisms whereby insulin controls Na⁺/K⁺-ATPase activity are discussed. These are tissue- and isoform-specific, and include reversible covalent modification of catalytic subunits, activation by a rise in intracellular Na⁺ concentration, altered Na⁺ sensitivity and changes in subunit gene or protein expression. Given the recent escalation in knowledge of insulin-stimulated signal transduction systems, it is pertinent to ask which intracellular signalling pathways are utilized by insulin in controlling Na⁺/K⁺-ATPase activity. Evidence for and against a role for the phosphatidylinositol-3-kinase and mitogen activated protein kinase arms of the insulin-stimulated intracellular signalling networks is suggested. Finally, the clinical relevance of Na⁺/K⁺-ATPase control by insulin in diabetes and related disorders is addressed.     

Outward sodium and potassium cotransport in human red cells

Summary This paper reports some kinetic properties of Na–K cotransport in human red cells. All fluxes were measured in the presence of 10^–4 M ouabain. We measured Na and K efflux from cells loaded by the PCMBS method to contain different concentrations of these ions into a medium that contained neither Na nor K (MgCl₂-sucrose substitution) in the absence and presence of furosemide. Furosemide inhibited 30–60% of the total efflux depending on the internal ion concentration and the individual subject. We took the furosemide-sensitive fluxes to be a measure of Na–K cotransport. The ratio of Na to K cotransport was 1 over the entire range of internal Na and K concentrations studied. When Na was substituted for K as the only internal cation, cotransport was maximally activated when the Na and K concentrations were between 20 and 90 mmol/liter cells. The concentration of internal Na required to produce half-maximal cotransport was about 13±4 mmol/liter cells (n=4), while the comparable concentration of K was somewhat lower. The activation curve was definitely sigmoid in character, suggesting that at least two Na ions are involved in the transport process. The maximum of Na–K cotransport was about 0.5±0.15 mmol/liter cells × hr (n=5); it had a flat maximum in the medium at about pH 7.0, decreasing in both the acid and alkaline sides. furosemide-resistant effluxes were found to be linear functions of internal Na and K concentrations and to yield rate coefficients of 0.019±0.002 hr^–1 and 0.014±0.002 hr^–1 (n=7), respectively. These values are of the same order of magnitude expected of ions moving across phospholipid bilayers.Charge de Recherches CNRS.     

Functional Consequences of Various Leucine Mutations in the M3/M4 Loop of the Na<Superscript>+</Superscript>,K<Superscript>+</Superscript>-ATPase α-Subunit

Leucines were mutated within the sequence L³¹¹ILGYTWLE³¹⁹ of the extracellular loop flanking the third (M3) and fourth (M4) transmembrane segments (M3/M4 loop) of the Torpedo Na⁺,K⁺-ATPase α-subunit. Replacement of Leu³¹¹ with Glu resulted in a considerable loss of Na⁺,K⁺-ATPase activity. Replacement of Leu³¹³ with Glu shifted the equilibrium of E₁P and E₂P toward E₁P and reduced the rate of the E₁P to E₂P transition. The reduction of the transition rate and stronger inhibition of Na⁺,K⁺-ATPase activity by Na⁺ at higher concentrations together suggest that there is interference of Na⁺ release on the extracellular side in the Leu³¹³ mutant. Thus, Leu³¹³ could be in the pathway of Na⁺ exit. Replacement of Leu³¹⁸ with Glu yielded an enzyme with significantly reduced apparent affinity for both vanadate and K⁺, with an equilibrium shifted toward E₂P and no alteration in the transition rate. The reduced vanadate affinity is due to the lower rate of production of vanadate-reactive [K⁺ ₂]E₂ caused by inhibition of dephosphorylation through reduction of the K⁺ affinity of E₂P. Thus, Leu³¹⁸ may be a critical position in guiding external K⁺ to its binding site.     

Palytoxin Acts on Na+,K+-ATPase but not Nongastric H+,K+-ATPase

Palytoxin (PTX) opens a pathway for ions to pass through Na,K-ATPase. We investigate here whether PTX also acts on nongastric H,K-ATPases. The following combinations of cRNA were expressed in Xenopus laevis oocytes: Bufo marinus bladder H,K-ATPase α₂- and Na,K-ATPase β₂-subunits; Bufo Na,K-ATPase α₁- and Na,K-ATPase β₂-subunits; and Bufo Na,K-ATPase β₂-subunit alone. The response to PTX was measured after blocking endogenous Xenopus Na,K-ATPase with 10 μm ouabain. Functional expression was confirmed by measuring ⁸⁶Rb uptake. PTX (5 nm) produced a large increase of membrane conductance in oocytes expressing Bufo Na,K-ATPase, but no significant increase occurred in oocytes expressing Bufo H,K-ATPase or in those injected with Bufo β₂-subunit alone. Expression of the following combinations of cDNA was investigated in HeLa cells: rat colonic H,K-ATPase α₁-subunit and Na,K-ATPase β₁-subunit; rat Na,K-ATPase α₂-subunit and Na,K-ATPase β₂-subunit; and rat Na,K-ATPase β₁- or Na,K-ATPase β₂-subunit alone. Measurement of increases in ⁸⁶Rb uptake confirmed that both rat Na,K and H,K pumps were functional in HeLa cells expressing rat colonic HKα₁/NKβ₁ and NKα₂/NKβ₂. Whole-cell patch-clamp measurements in HeLa cells expressing rat colonic HKα₁/NKβ₁ exposed to 100 nm PTX showed no significant increase of membrane current, and there was no membrane conductance increase in HeLa cells transfected with rat NKβ₁- or rat NKβ₂-subunit alone. However, in HeLa cells expressing rat NKα₂/NKβ₂, outward current was observed after pump activation by 20 mm K⁺ and a large membrane conductance increase occurred after 100 nm PTX. We conclude that nongastric H,K-ATPases are not sensitive to PTX when expressed in these cells, whereas PTX does act on Na,K-ATPase.     

Intracellular calcium content of human erythrocytes: Relation to sodium transport systems

Summary To study the possible role of intracellular Ca (Ca _i ) in controlling the activities of the Na⁺–K⁺ pump, the Na⁺–K⁺ cotransport and the Na⁺/Li⁺ exchange system of human erythrocytes, a method was developed to measure the amount of Ca embodied within the red cell. For complete removal of Ca associated with the outer aspect of the membrane, it proved to be essential to wash the cells in buffers containing less than 20nm Ca. Ca was extracted by HClO₄ in Teflon^® vessels boiled in acid to avoid Ca contaminations and quantitated by flameless atomic absorption. Ca _i of fresh human erythrocytes of apparently healthy donors ranged between 0.9 and 2.8 mol/liter cells. The mean value found in females was significantly higher than in males. The interindividual different Ca contents remained constant over periods of more than one year. Sixty to 90% of Ca _i could be removed by incubation of the cells with A23187 and EGTA. The activities of the Na⁺–K⁺ pump, of Na⁺–K⁺ cotransport and Na⁺/Li⁺ exchange and the mean cellular hemoglobin content fell with rising Ca _i ; the red cell Na⁺ and K⁺ contents rose with Ca _i . Ca depletion by A23187 plus EGTA as well as chelation of intracellular Ca²⁺ by quin-2 did not significantly enhance the transport rates. It is concluded that the large scatter of the values of Ca _i of normal human erythrocytes reported in the literature mainly results from a widely differing removal of Ca associated with the outer aspect of the membrane.