骨骼肌肌浆网Na+，K+-ATP酶和Ca2+-ATP酶活性在不同训练条件下的变化

背景：Na+,K+-ATP酶和Ca2+-ATP酶在物质运送、能量转换以及信息传递方面具有重要作用。肌浆网在肌肉兴奋-收缩耦联过程中起关键作用,与运动性骨骼肌疲劳的发生密切关。 目的：通过建立SD大鼠有氧和无氧训练模型,观察不同训练负荷条件对大鼠骨骼肌肌浆网Na+,K+-ATP酶和Ca2+-ATP酶活性的影响。 方法：参照Bedford TG标准,建立有氧和无氧运动大鼠跑台训练模型,有氧运动组采用递增负荷训练,无氧运动组采用高速间歇训练,正常对照组大鼠正常笼内生活,不运动。各组动物训练结束后用超速离心法提取大鼠骨骼肌肌浆网,紫外分光光度计检测大鼠骨骼肌肌浆网Na+,K+-ATP酶和Ca2+-ATP酶的活性。 结果与结论：训练4周后,两个运动组大鼠骨骼肌肌浆网Na+,K+-ATP酶和Ca2+-ATP酶的活性逐渐升高(P < 0.05);训练6周,仅有氧运动组升高(P < 0.05),无氧运动组则活性降低(P < 0.05)。结果提示有氧训练更有利于保护大鼠骨骼肌肌浆网Na+,K+-ATP酶和Ca2+-ATP酶的活性,但需要一定的时间累积。     

丙泊酚可调节缺血再灌注损伤脊髓Ca2+, Mg2+, Cu2+，Zn2+的平衡

检测血清和脊髓匀浆中Ca2+、Mg2+、Cu2+、Zn2+的变化规律,揭示丙泊酚对缺血再灌注损伤脊髓保护作用的可能机制。结果发现,随着缺血再灌注损伤时间的延长,兔血清Ca2+,Cu2+浓度逐渐升高,Mg2+,Zn2+浓度逐渐下降,至脊髓损伤后7d,以上离子变化最明显;缺血再灌注损伤7 d,兔缺血脊髓匀浆中的各离子浓度变化与血清中相一致。给予丙泊酚干预后,缺血再灌注期间兔血清和脊髓匀浆中Ca2+、Mg2+、Cu2+、Zn2+浓度均无显著的波动。提示丙泊酚可通过稳定或恢复脊髓缺血再灌注损伤区金属离子的平衡发挥对脊髓缺血再灌注损伤的保护作用。     

脑缺血病人血小板肌球蛋白轻链激酶和Ca2+、Mg2+-ATP酶活性及其与[Ca2+]i关系的研究

目的探讨急性缺血性脑血管病血小板肌球蛋白轻链激酶（ＭＬＣＫ）和Ｃａ２＋、Ｍｇ２＋－ＡＴＰ酶活性的变化及与血小板胞浆游离钙浓度［Ｃａ２＋］ｉ的关系。方法用３２Ｐ同位素掺入法和比色法分别测定５８例脑缺血病人,及３５名健康对照者血小板ＭＬＣＫ和Ｃａ２＋、Ｍｇ２＋－ＡＴＰ酶活性。用荧光钙指示剂Ｆｕｒａ－２负载血小板扫描的方法,测定脑缺血病人血小板［Ｃａ２＋］ｉ浓度。结果ＴＩＡ组和脑梗死组ＭＬＣＫ活性与对照组相比均有明显增加（Ｐ＜０．０１）,而Ｃａ２＋Ｍｇ２＋－ＡＴＰ酶活性均低于对照组（Ｐ＜０．０５,Ｐ＜０．０１）。ＴＩＡ组和脑梗死组血小板静息［Ｃａ２＋］ｉ;均高于对照组;血小板静息［Ｃａ２＋］ｉ与血小板ＭＬＣＫ活性呈显著正相关（Ｐ＜０．０１）,而与血小板Ｃａ２＋、Ｍｇ２＋－ＡＴＰ酶活性呈负相关（Ｐ＜０．０５）。结论血小板ＭＬＣＫ和Ｃａ２＋、Ｍｇ２＋－ＡＴＰ酶活性与急性缺血性脑血管病的发生有密切关系,ＭＬＣＫ活性的变化可能是脑缺血病人血小板活化的分子基础。     

一氧化碳对局灶性脑缺血脂质过氧化物及Na+-K+ ATP酶的影响

目的　研究一氧化碳对局灶性脑缺血脑组织脂质过氧化物及Na K ATP酶的影响 ,试图从亚细胞水平阐明CO对脑组织保护作用的机理。方法　将SD大鼠随机分为三组 (n =6 ) ,使用HO诱导剂、HO抑制剂腹腔注射为实验组 ,等量生理盐水作为对照组腹腔注射 ,12h后制成MCAO模型。栓塞后 2 4h检测CO浓度、脂质过氧化及Na K ATP酶活性。结果　与对照组相比 ,HO诱导剂组CO浓度明显升高 ,MDA减少 ,SOD及Na K ATP酶增高 (各为P <0 .0 1、P <0 .0 1、P <0 .0 5、P <0 .0 5 ) ,而HO抑制剂组CO浓度明显降低 ,MDA增加 ,SOD及Na K ATP酶活性降低 (各为P <0 .0 0 1、P <0 .0 5、P <0 .0 5、P <0 .0 5 )。HO诱导剂、HO抑制剂对非栓塞侧脑组织脂质过氧化物及Na K ATP酶的活性没有影响 (P >0 .0 5 )。结论　CO是一种信使分子 ,通过减少自由基、增加SOD及Na K ATP酶活性对局灶性缺血的脑组织起保护作用     

高温对重型颅脑损伤后乳酸、Na+-K+-ATP酶和脑水肿的影响

目的 探讨大鼠重型颅脑损伤后高温对伤灶区脑组织乳酸、Na+-K+-ATP酶和脑水肿的影响.方法 90只SD大鼠随机分为假手术组、颅脑损伤组、伤后高温组,每组又按处死时间点(伤后4 h、1 d、3 d、5 d和7 d)分为五个亚组,每亚组6只.取伤灶区脑组织测含水量、乳酸含量和Na+-K+-ATP酶活性并行电镜检查.结果 高温组脑组织含水量和乳酸含量在伤后各时间点均显著高于颅脑损伤组和假手术组(P＜0.05),而Na+-K+-ATP酶含量显著低于颅脑损伤组和假手术组(P＜0.05),电镜检查发现高温组神经细胞肿胀、血脑屏障破坏程度较颅脑损伤组明显加重.结论 颅脑损伤后高温增加脑组织乳酸生成,同时Na+-K+-ATP酶活性下降,脑水肿加重,故在颅脑损伤后应保持体温在正常范围内,避免体温升高.     

慢性大鼠酒精中毒钙神经素在脑内的分布与表达及离子改变

目的 检测慢性酒精中毒大鼠脑组织钙神经素(calcineurin,CaN)的异常分布与表达及离子变化情况,探讨慢性酒精中毒代谢性脑病的发病机制.方法 选用健康雄性Wistar大鼠100只,随机分为2组,酒精中毒组60只,盐水对照组40只.正常喂养1w后开始造模.酒精中毒组(60只):每日每只大鼠分别按8ml/kg灌胃2w,随后再按照10ml/kg灌胃1w,按12ml/kg灌胃1w,共灌胃4w.每日灌胃2次,其间隔均为6h,酒精浓度为50％.盐水对照组(40只):同时用等量的生理盐水进行灌胃.每周测量体重,观察其一般生物学特征;免疫组化法测定CaN的阳性表达;原子吸收法测定Ca2、Mg2+、K+、Na+等微量元素变化.结果 两组大鼠一般生物学特征存在明显差异,体重差异具有的统计学意义;酒精组大鼠大脑皮质、海马CaN表达明显多于对照组(p＜0.05),小脑CaN表达无差异(P＞0.1);原子吸收法测定酒精组的Ca2含量比正常对照组明显增多(P＜0.05),Mg2、K+、Na+含量无显著变化(P＞0.05).结论 慢性酒精中毒后可以引起大鼠大脑皮质、海马CaN异常表达及Ca2+含量明显增多,推测酒精中毒后可对神经元产生以Ca2+代谢为主的影响,导致酒精中毒性代谢性脑病的发生.     

不同运动方式和时间对大鼠骨骼肌线粒体呼吸链复合体酶Ⅰ和Ⅳ活性的

背景：急性剧烈运动对机体可造成氧化应激,线粒体生成活性氧造成机体氧化应激和钙离子超负荷,导致骨骼肌功能下降,机体产生疲劳。然而长期规律运动后线粒体产生适应性变化,从而起到保护机体免受过多活性氧损害的作用。 目的：观察不同运动方式和时间对大鼠骨骼肌线粒体呼吸链复合体酶Ⅰ,Ⅳ活性的影响。 方法：48只健康雄性SD大鼠随机等分为正常对照组、无氧运动组、有氧运动组和交替运动组。在大鼠运动2,4,6周的时候分别处死,差速离心提取大鼠骨骼肌线粒体,分光光度法测定线粒体呼吸链复合体酶Ⅰ,Ⅳ的活性。 结果与结论：运动后有氧组、交替组与无氧组线粒体呼吸链复合体酶I的活性随时间先增强而后下降;运动后有氧组与交替组线粒体呼吸链复合体酶Ⅳ的活性随时间而增强,无氧组则下降。说明有氧运动在中长期耐力运动中可有效提高大鼠体内呼吸链复合体酶Ⅰ,Ⅳ的活性,而无氧运动则只能在短期内提高其活性,长时间无氧运动可能导致对线粒体呼吸链复合体酶的损伤,影响骨骼肌工作效率,造成机体疲劳。     

2型糖尿病患者C肽与红细胞膜Na+-K+ ATPase及血浆NOS活性的关系

目的 观察C肽与 2型糖尿病患者红细胞膜ATP酶及血浆NOS活性的关系.方法 172例实验对象分为健康对照组、2型糖尿病胰岛素组与口服药物组3组,记录年龄、病程、C肽、空腹血糖、糖化血红蛋白等指标,酶比色法测定红细胞膜Na+-K+ ATPase及血浆NOS水平并进行比较,分析其与 C肽等指标的相关性.结果 胰岛素组Na+-K+ -ATPase及NOS活性较口服药物组低,P<0. 05;胰岛素组红细胞膜Na+-K+-ATPase及NOS活性与C肽水平呈正相关,与病程呈负相关,口服药物组Na+-K+-ATPase及NOS活性仅与C肽水平呈正相关.结论 C肽参与了Na+-K+-ATPase及NOS活性的维持,可能有延缓糖尿病微血管并发症的发生发展的作用.     

神经节苷脂对NIDDM神经病变患者Na~ -K~ -ATP酶和NCV的影响

本文应用神经节苷脂（ＧＡ）治疗非胰岛素依赖型糖尿病（ＮＩＤＤＭ）神经病变患者，发现ＧＡ明显增加ＮＩＤＤＭ神经病变患者红细胞膜Ｎａ＋Ｋ＋ＡＴＰ酶活性，神经传导速度（ＮＣＶ）呈不同程度改善。结果提示：在ＮＩＤＤＭ神经病变治疗方面，ＧＡ可能具有重要的应用价值     

钙离子ATP酶2a基因修饰骨髓间充质干细胞移植改善慢性心力衰竭大鼠的心功能***☆

背景：目前仍缺乏有效手段修复心力衰竭后受损心肌，逆转心肌病理性重塑。作为一种新的治疗策略，用正常肌细胞和治疗性基因干预受损心肌正逐渐显示出其在改善心功能方面的优势。 目的：观察腺病毒转染不同代骨髓间充质干细胞的有效性和稳定性。并以携带肌浆网钙离子ATP酶（sarcoplasmic reticulum Ca(2+) ATPase，SERCA2a) 基因的腺病毒转染骨髓间充质干细胞，治疗心力衰竭大鼠，比较SERCA2a基因治疗，骨髓间充质干细胞移植以及骨髓干细胞基础的SERCA2a基因治疗慢性心力衰竭大鼠的效果。 设计：随机对照实验。 单位：解放军总医院老年心血管病科和北京医科大学生物化学系。 材料：选取购于北京医科大学动物实验中心的4周龄雄性SD大鼠作为骨髓供体。选取体质量200~250 g雌性成年SD大鼠作为细胞移植和基因治疗受体。以雄性大鼠Y染色体sry基因鉴定供体移植细胞是否在雌性大鼠受体心肌内存活。实验所用Ad-SERCa2a，Ad-EGFP的构建由我科鲁小春博士完成；第3和8代骨髓间充质干细胞自行分离培养。 方法：实验于2004-07/2005-12在北京医科大学生物化学系周春燕实验室完成。对30只雌性SD大鼠进行左冠状动脉结扎，制作急性心肌梗死后慢性心力衰竭大鼠模型。将造模成功的29只大鼠随机分为4组：基因治疗组7只，干细胞移植治疗组7只，基因修饰的干细胞移植组8只，腺病毒空载体对照组7只，分别予以单纯SERCA2a基因、MSC移植、SERCA2a基因修饰的骨髓间充质干细胞移植及腺病毒空载体干预。分离培养大鼠骨髓间充质干细胞，用携带SERCA2a及绿色荧光蛋白的腺病毒（Ad-SERCA2a-GFP）转染第3和8代骨髓间充质干细胞。 主要观察指标：采用流式细胞仪检测不同代骨髓间充质干细胞的Ad-SERCA2a-GFP转染率。分别在治疗前及治疗后14，21 d采用超声心动图检测大鼠心功能。采用免疫组化法检测大鼠心脏Ⅷ因子表达；采用RT-PCR 和Western杂交检测SERCA2a的基因和蛋白水平表达，并按照说明书检测宿主SERCA2a功能活性。 结果：①转染率：腺病毒转染不同代骨髓间充质干细胞的转染率超过80%，第3代骨髓间充质干细胞与第8代的转染率比较，差异无显著性意义（P > 0.05）。②大鼠心功能：治疗后14 d，与腺病毒空载体对照组相比，其余3组左室射血分数均明显升高（P < 0.01）。治疗后 21 d，与腺病毒空载体对照组相比，干细胞移植治疗组和基因修饰的干细胞移植组大鼠室壁增厚；干细胞移植治疗组和基因修饰的干细胞移植组左室射血分数和左室短轴缩短率改善率持续升高（P < 0.01），基因治疗组两指标改善率较治疗14 d时下降。与腺病毒空载体对照组相比，基因修饰的干细胞移植组左室前壁和室间隔收缩期纵向峰值速度显著升高（P < 0.01），左室前壁和室间隔舒张期纵向峰值速度亦呈现相同改善(P < 0.01)。③心肌SERCA2a的基因、蛋白水平表达和功能活性，以及Ⅷ因子表达：携带SERCA2a基因的骨髓干细胞在宿主心肌能有效地合成和表达有功能的SERCA2a蛋白。与腺病毒空载体对照组相比，基因修饰的干细胞移植组SERCA2a基因、蛋白表达和酶活性均显著增强。干细胞移植组心力衰竭大鼠心脏瘢痕区可观察到Ⅷ因子表达。 结论：①第3和8代骨髓间充质干细胞均具有高腺病毒转染率，骨髓间充质干细胞是基因治疗的良好细胞载体，其介导的SERCA2a基因治疗对衰竭心肌具有持续稳定的心功能改善作用。②骨髓间充质干细胞移植改善心功能的作用可能与促进血管新生有关。     

Plasmalemmal and mitochondrial Na+‐Ca2+ exchange in neuroglia

In the absence of the electrical signaling for which neurons are so highly specialized, GLIA rely on the slow propagation of ionic signals to mediate network events such as Ca²⁺ and Na⁺ waves. Glia differ from neurons in another important way, they are replete with a high density of ionic‐transport proteins that are essential for them to fulfil their basic functions as guardians of the intra and extra‐cellular milieux. Both the signaling and the homeostatic properties of glial cells are therefore particularly dependent upon the regulation of the two principle physiological metal cations, Ca²⁺ and Na⁺. For both ions, glia express high‐affinity/low capacity ATP‐fuelled pumps that can rapidly move small numbers of ions against an electro‐chemical gradient. For both Ca²⁺ and Na⁺ regulation, a single transporter family, the Na⁺‐Ca²⁺ exchanger (NCX), is used to maintain cellular ion homeostasis over the longer term and under conditions of prolonged or acute ionic dysregulation in astrocytes, oligodendroglia and microglia. Our understanding of glial NCX, both plasmalemmal and mitochondrial, is undergoing the kind of transformation that our understanding of glial cells, in general, has undergone in recent decades. These exchange proteins are becoming increasingly recognized for their essential roles in intracellular homeostasis while their signaling functions are starting to come to light. This review summarizes these key aspects and highlights the many areas where work has yet to begin in this rapidly evolving field. GLIA 2016;64:1646–1654     

Effect of neonatal hypothyroidism on the kinetic properties of Na+, K+ -ATPase from rat brain microsomes

The effects of neonatal hypothyroidism on the kinetic properties of Na+, K+ -ATPase from rat brain microsomes were examined. Neonatal hypothyroidism resulted in decreased Na+, K+ -ATPase activity compared to control samples (7.4 +/- 1.48 and 29.8 +/- 2.30 micromol Pi/h/mg protein, respectively, P < 0.001). Substrate kinetics studies with ATP, Na+ and K+ revealed that there were generalised decreases in Vmax. For ATP, Na+ and K+, activities resolved into two kinetic components in the control group. In hypothyroid animals, the low-affinity component for ATP was absent. The opposite pattern (i.e. an absence of the high-affinity component) was noted for Na+. For K+, although both kinetic components were discernible in neonatal hypothyroid brain microsomes, the Km of the high-affinity component was significantly higher (P < 0.001) compared to control samples. In the control group, the enzyme displayed allosteric behaviour at high concentrations of Mg2+; in hypothyroid animals, the pattern was completely allosteric. The Na+, K+ -ATPase enzyme from the hypothyroid brain microsomes bound two molecules of ATP rather than one, unlike in the control animals. Our results thus indicate that neonatal hypothyroidism results in an impairment of microsomal Na+, K+ -ATPase activity in the rat brain, together with subtle alterations in the kinetic properties of the enzyme.     

The influence of MK-801 on the hippocampal free arachidonic acid level and Na+,K+-ATPase activity in global cerebral ischemia-exposed rats

The influence of 20 min global cerebral ischemia on the free arachidonic acid (FAA) level and Na⁺,K⁺-ATPase activity in the rat hippocampus at different time points after ischemia was examined. In addition, the effect of MK-801 on mentioned parameters was studied. Animals were exposed to 20 min global cerebral ischemia and were sacrificed immediately, 0.5, 1, 2, 6, 24, 48, 72, and 168 h after ischemic procedure. The level of the FAA and the Na⁺,K⁺-ATPase activity was measured during all reperfusion periods examined. Various doses of MK-801 (0.3, 1.0, 3.0, and 5.0 mg/kg) had been injected 30 min before ischemic procedure started. It was found that 20 min global cerebral ischemia induces a statistically significant increase of the FAA level immediately after ischemia and during the first 0.5 h of reperfusion. After a transient decrease, the level of FAA level increased again after 24 and 168 h of recirculation. Treatment with 3.0 mg/kg of MK-801 significantly prevented the FAA accumulation immediately and 0.5 h after ischemic insult while application of 5.0 mg/kg of MK-801 exerted a protective effect during the first 24 h. Global cerebral ischemia induces the significant decline in the Na⁺,K⁺-ATPase activity in the hippocampus starting from 1 to 168 h of reperfusion. Maximal inhibition was obtained 24 h after the ischemic damage. Application of 3.0 mg/kg of MK-801 exerted statistically significant protection during the first 24 h while the treatment with 5.0 mg/kg of MK-801 prevented fall in enzymatic activity during all reperfusion periods examined. Our results suggest that, in spite of different and complex pathophysiological mechanisms involved in the increase of FAA level and the decrease of the Na⁺,K⁺-ATPase activity, blockade of NMDA receptor subtype provides a very important strategy for the treatment of the postischemic excitotoxicity.     

Effect of Na+, K(+)-ATPase modifiers on high-affinity ouabain binding determined by quantitative autoradiography.

There is growing evidence on the existence of endogenous ouabain-like factors that modulate Na+, K(+)-ATPase activity. In this laboratory, two soluble subfractions (peaks I and II) were previously separated from rat cerebral cortex, which had opposite effects on Na+, K(+)-ATPase activity. Peak I stimulated and peak II inhibited the enzyme (Rodríguez de Lores Arnaiz and Antonelli de Gómez de Lima, Neurochem Res 11:933-947, 1986). The same effects are now reported for K(+)-p-nitrophenyphosphatase activity. Localization of high-affinity ouabain binding in rat brain was done by quantitative autoradiography using a microcomputer digital imaging system. Peak I did not modify, whereas peak II blocked ouabain binding in areas 3-4 of cerebral cortex, dentate gyrus, stria terminalis, thalamic nuclei, and basal ganglia. Similar results were obtained when ouabain binding was determined in rabbit cerebral cortex and by a conventional filtration assay in nerve ending membranes obtained from rat cerebral cortex. These results favour the idea that the factor present in peak II fraction might behave as an ouabain-like substance.     

Intrastriatal methylmalonic acid administration induces convulsions and TBARS production,and alters Na+,K+-ATPase activity in the rat striatum and cerebral cortex

PURPOSE: Methylmalonic acid (MMA) inhibits succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase activity in vitro. Acute intrastriatal administration of MMA induces convulsions through glutamatergic mechanisms probably involving primary adenosine triphosphate (ATP) depletion and free radical generation. In this study we investigated whether the intrastriatal administration of MMA causes lipoperoxidation and alteration in Na+, K+-ATPase activity ex vivo and characterized the electrographic changes elicited by the intrastriatal administration of this organic acid. METHODS: MMA-induced lipoperoxidation, alterations in Na+, K+-ATPase activity and electrographic changes were measured by measuring total thiobarbituric acid-reacting substances and inorganic phosphate release by spectrophotometry, and by depth electrode recording, respectively. RESULTS: We demonstrated that intrastriatal MMA (6 mmol) injection causes convulsive behavior and electrographically recorded convulsions that last approximately 2 h. Concomitant with the increase of thiobarbituric acid-reacting substances (TBARS) content, we observed a significant inhibition of Na+,K+-ATPase activity in the striatum, and activation of Na+,K+-ATPase activity in the ipsilateral cerebral cortex. Intrastriatal MMA injection increased the content of TBARS in the striatum measured 30 min (32.4 +/- 12.0%, compared with the noninjected contralateral striatum) and 3 h (39.7 +/- 5.1%, compared with the noninjected contralateral striatum) after MMA injection. TBARS content of the ipsilateral cerebral cortex increased after MMA injection at 30 min (42.1 +/- 6.0%) and 3 h (40.4 +/- 20.2%), and Na+,K+-ATPase activity in the ipsilateral cerebral cortex increased during ictal activity (113.8 +/- 18%) and returned to basal levels as electrographic convulsions vanished in the cortex. Interestingly, intrastriatal MMA administration induced a persistent decrease in Na+,K+-ATPase activity only in the injected striatum (44.9 +/- 8.1% at 30 min and 68.7 +/- 9.4 at 3 h). CONCLUSIONS: These data suggest that MMA induces lipoperoxidation associated with Na+,K+-ATPase inhibition or activation, depending on the cerebral structure analyzed. It is suggested that Na+,K+-ATPase inhibition may play a primary role in generating MMA-induced convulsions.     

Ultracytochemical demonstration of the polarity of Ca2+-ATPase activity in microglia

In order to investigate plasma membrane Ca²⁺-ATPase (Ca²⁺-ATPase) activity in three subsets of microglia/macrophages (microglia in perineuronal regions (perineuronal microglia)), microglia in contact with the parenchymal side of the vascular basal lamina (juxtavascular microglia) and perivascular cells within the basal lamina), we performed an ultracytochemical study using a lead salt technique in rat cerebral cortices. In 60.6% of perineuronal microglia, the cytochemical reaction (CR) for Ca²⁺-ATPase on the plasma membrane (PM) in the vicinity of neurons was stronger than the CR on the other side of the PM, and deposits of the reaction product (RP) for Ca²⁺-ATPase had accumulated, reflecting the polarity of Ca²⁺-ATPase activity. In contrast, in all of juxtavascular microglia and perivascular cells, deposits of the RP were distributed evenly along the PM without polarity. These results suggest that the polarity of the Ca²⁺-ATPase activity manifests certain functional interactions between perineuronal microglia and neurons.     

Neonatal status convulsivus, spongiform encephalopathy, and low activity of Na+/K(+)-ATPase in the brain.

The first and second child of a family died from neonatal seizures with no detectable brain malformation, metabolic, infectious, or chromosomal etiology. Neuropathological examination of the brain of the second child who died at 11 days revealed a widespread spongy state and a selective vulnerability of the astrocytes characterized by numerous enlarged bare astrocytic nuclei and different forms of astrocyte degeneration. The glial cells were strongly positive for glial fibrillary acidic protein and vimentin immunocytochemical reaction. Cortical measurement of Na+/K(+)-ATPase revealed very low enzyme activity. We hypothesize that a defect of Na+/K(+)-ATPase of the astrocytes could be the common pathogenetic factor for the congenital status convulsivus and for the spongy state.     

Na+,K+-ATPase concentration and fiber type distribution after spinal cord injury

Complete spinal cord injury (SCI) is characterized, in part, by reduced fatigue-resistance of the paralyzed skeletal muscle during stimulated contractions, but the underlying mechanisms are not fully understood. The effects of complete SCI on skeletal muscle Na(+),K(+)-adenosine triphosphatase (ATPase) concentration, and fiber type distribution were therefore investigated. Six individuals (aged 32.0 +/- 5.3 years) with complete paraplegia (T4-T10; 1-19 years since injury) participated. There was a significantly lower Na(+),K(+)-ATPase concentration in the paralyzed vastus lateralis (VL) when compared to either the subjects' own unaffected deltoid or literature values (from our laboratory, utilizing the same methodology) of VL Na(+),K(+)-ATPase concentration for the healthy able-bodied (141.6 +/- 50.0, 213.4 +/- 23.9, 339 +/- 16 pmol/g wet wt., respectively; P < 0.05). There was also a significant negative correlation between the Na(+),K(+)-ATPase concentration in the paralyzed VL and years since injury (r = -0.75, P < 0.05). These findings are clinically relevant as they suggest that reductions in Na(+),K(+)-ATPase contribute to the fatigability of paralyzed muscle after SCI. Unexpectedly, the VL muscles of our subjects had a higher proportion of their area represented by type I fibers compared to literature values for the VL of the healthy able-bodied (52.6 +/- 25.3% vs. 36 +/- 11.3%, respectively; P < 0.05). As all our subjects had upper motor neuron injuries and, therefore, experienced muscle spasticity, our findings warrant further investigation into the relationship between muscle spasticity and fiber type expression after SCI.     

Acute and chronic regulation of Na+/K+-ATPase transport activity in the RN22 Schwann cell line in response to stimulation of cyclic AMP production

Na⁺/K⁺-ATPase-dependent Rb⁺ uptake of RN22 Schwann cells was stimulated by cholera toxin (0.25 μg/ml), forskolin (2 mM), or 8-bromo cAMP (1 mM). At 2 h Rb⁺ uptake was increased by 162 ± 6% (cholera toxin), 151 ± 14% (forskolin), and 207 ± 15% (8-bromo cAMP). Cholera toxin or 8-bromo cAMP treatment for 12–24 h resulted in a second peak of Na⁺/K⁺-ATPase-dependent Rb⁺ transport activity of 186 ± 12 and 265 ± 9% of control, respectively. Cholera toxin also transiently stimulated the activity of the Na⁺, K⁺, 2Cl⁻-cotransporter with a peak at 2 h (179 ± 9%), returning to basal levels by 24 h. Inhibition of the Na⁺,K⁺,2Cl⁻-cotransporter by bumetanide (0.1 mM) or by reduction of the Na⁺ gradient (10 mM veratridine treatment) prevented the early peak in ATPase activity but not the second peak. These results indicated that the early transient stimulation of Na⁺/K⁺ ATPase activity by cholera toxin was due to an increase in cellular Na⁺, secondary to stimulation of Na⁺,K⁺,2Cl⁻-cotransport activity. Western blot analysis of cellular homogenates and purified membrane fractions showed that the second peak of Rb⁺ uptake activity was a result of translocation of transport protein from an intracellular microsomal pool to the plasma membrane. Rb⁺ uptake by dominant negative protein kinase A mutants of the RN22 cell was not stimulated by cholera toxin treatment (acute or chronic) confirming the cAMP/protein kinase A dependency of both acute and long-term regulation of transport activity. In the absence of a change in Michaelis constants or of an increase in total transport protein of cellular homogenates, neither a change in enzyme kinetics nor an increase in de novo synthesis of transport protein could account for the increase in transport activity. GLIA 23:349–360, 1998. © 1998 Wiley-Liss, Inc.