衰竭心肌能量代谢重构及相关受体的表达

目的比较正常和衰竭心肌组织相关酶活性及β3肾上腺素能受体（β3受体）、过氧化物酶体增生物激活受体α（PPARα受体）基因和蛋白表达的变化,探讨心力衰竭（心衰）代谢重构的可能机制。方法选取20例瓣膜置换术的心衰患者和6例意外伤亡健康者心肌组织,检测心肌游离脂肪酸（FFA）、琥珀酸脱氢酶（SDH）和ATP酶活力。应用RT-PCR和Western-blot方法分别检测心肌组织β3受体和PPARα受体mRNA和蛋白表达。结果衰竭心肌FFA含量明显增加（P〈0．01）;SDH、Na^＋-K^＋-ATP酶和Ca^2＋-Mg^2＋-ATP酶活性则显著降低（P〈0．01,P〈0．05和P〈0．01）。衰竭心肌β3受体mRNA和蛋白表达明显高于正常心肌;而PPARα受体表达则显著低于正常心肌。结论心衰时存在代谢重构,表现为心肌代谢底物发生转变,代谢相关酶活性下降等;β3受体和PPARα受体在衰竭心肌分别上调和下调,可能参与心肌组织代谢重构。     

甲状腺功能减退大鼠心肌抗氧化能力及ATP酶活性的实验研究

目的 研究甲状腺功能减退大鼠心肌抗氧化能力及心肌膜标志酶活性的变化，探讨甲状腺功能减退致心肌损伤的发病机制。方法 30只Wistar大鼠随机分为对照组和甲状腺功能减退组，用低碘饲料和不含碘的水喂养大鼠复制甲状腺功能减退动物模型。制备心肌组织匀浆，提取心肌生物膜，测定心肌组织丙二醛（MDA）水平、谷胱甘肽过氧化物酶（GSH—Px）和超氧化物歧化酶（SOD）活性及心肌生物膜Na^＋，K^＋-ATP酶、Mg^2＋-ATP酶、Ca^2＋-ATP酶、Ca^2＋，Mg^2＋-ATP酶活性。结果 与对照组比较，甲状腺功能减退组血清T3、T4均明显下降（P〈0．05或〈0．01）：心肌组织MDA水平和GSH—Px活性明显升高（P〈0．05），而SOD活性明显降低（P〈0．05）；心肌生物膜Na^＋，K^＋-ATP酶、Ca^2＋-ATP酶、Mg^2＋-ATP酶、Ca^2＋，Mg^2＋-ATP酶活性明显下降（P〈0．05）。结论 甲状腺功能减退时心肌抗氧化能力下降，心肌过氧化损伤，表现为心肌膜上参与代谢的ATP酶活性降低。     

大蒜素对鼠缺血再灌注心肌过氧化物酶体增殖物激活受体α表达的影响

目的：探讨大蒜素对实验性大鼠缺血再灌注心肌梗死面积及过氧化物酶体增殖物激活受体α（PPARα）表达的影响。方法：Wistar大鼠70只被随机分为三组：假手术组（n=24），缺血再灌注组（n=24），大蒜素组（n=22）。采用鼠心冠状动脉左前降支结扎法制作在体缺血再灌注模型，观察心肌梗死范围，运用半定量RT-PCR方法对心肌PPARα mRNA的表达情况进行分析，运用Western—blotting方法对检测PPAR蛋白表达情况。结果：大蒜素组心肌梗死面积显著减少（P〈0．05），并且心肌PPARα mRNA及蛋白表达水平显著上调（P〈0．01）。结论：大蒜素可显著减少实验性大鼠缺血再灌注后梗死面积及并使心肌中过氧化物酶体增殖物激活受体α（PPARα）显著上调。     

雌激素受体α和β及孕激素受体在胃癌中的表达及意义

运用Picture^TM-PV6000免疫组化技术检测48例胃癌及癌旁组织中雌激素受体α（ERα）和β（ERβ）、孕激素受体（PR）的表达。结果发现ERα和PR阳性染色只在细胞核内，在癌组织中表达阳性率分别为33．3％和29．2％。而癌旁组织均无表达，P〈0．001，ERβ主要表达在细胞核内。在癌组织和癌旁组织表达阳性率分别为70．8％和72．9％，P〈0．05。PR表达与ERα有高度相关性（P〈0．01）。而与ERβ无相关性。ERα和ERβ、PR三者共同表达阳性率18．75％，明显高于ERα、PR共表达（2．08％）或ERβ、PR共表达（6．25％），P〈0．01。Borrmann分型Ⅲ＋Ⅳ型（浸润型癌）者ERα阳性率（42．4％）显著高于BorrmannⅠ＋Ⅱ型（局限型癌）者（13．3％）。P〈0．05；有淋巴和远处转移者阳性率显著高于无转移者（P〈0．05）IERα和孕激素受体在印戒细胞癌、黏液腺癌、低分化腺癌等分化低的胃癌中表达较高，在中、高分化胃癌中表达较低。但无显著差异，与年龄、性别、肿瘤大小、部位和浸润深度无明显相关性。认为ERα、ERβ及PR在胃癌中均有表达，ERβ占优势IERα在胃癌中表达高于癌旁组织。并与胃癌Borrmann分型、淋巴和远处转移相关。ERα、ERβ及PR阳性胃癌是性激素依赖性肿瘤，可行内分泌治疗，并应针对ERα和ERβ的不同表达选择药物。     

压力超负荷对大鼠心肌PPARα和MCAD mRNA表达的影响

目的 :了解压力负荷性肥厚心肌过氧化物酶体活化受体α(PPARα)和中链脂酰基辅酶A脱氢酶(MCAD)mRNA的表达变化 ,探讨PPARα对肥厚心肌脂肪酸 β氧化关键酶基因表达的调控作用及肥厚心肌能量底物的变化。方法 :观察大鼠腹主动脉缩窄术后 1、4、8、16周血流动力学参数、心室重塑指标、血清和心肌游离脂肪酸 (FFA)的含量及PPARα和MCADmRNA的表达变化。结果 :随着肥厚程度的增加 ,血清和心肌FFA蓄积增加 ,心肌PPARα和MCADmRNA的表达也逐渐下调 ,且与脂肪酸的利用下调相一致。结论 :肥厚心肌PPARα活性下调 ,与MCAD基因表达变化一致 ;PPARα在转录水平调控脂肪酸氧化酶基因的表达 ;PPARα与肥厚心肌能量底物转换密切相关     

阿托伐他汀通过PPARβ／δ信号通路下调衰老心肌TNF-α表达的研究

目的：观察阿托伐他汀下调老年大鼠心肌肿瘤坏死因子-α（TNF-α）表达的作用及其与过氧化物酶体增殖物激活型受体β／δ（PPARβ／δ）信号通路之间的关系。方法：分离培养24个月龄大鼠的心肌细胞,将心肌细胞分为空白对照组、溶剂对照组、阿托伐他汀组、阿托伐他汀＋PPARβ／δ拮抗剂GSK0660组。各组细胞分别加入细胞培养液、二甲基亚砜（DMSO）、阿托伐他汀、阿托伐他汀＋GSK0660处理。用RT—PCR方法检测各组大鼠衰老心肌细胞的TNF-αmRNA表达水平,用westernblot方法检测各组TNF-α蛋白含量。结果：（1）与空白对照组相比,溶剂对照组大鼠衰老心肌细胞的TNF-α mRNA和蛋白水平均无显著差异;（2）与空白对照组相比,阿托伐他汀组的TNF-α mRNA和蛋白水平含量均显著降低（P〈0．01）;（3）阿托伐他汀＋GSK0660组的TNF-α mRNA表达水平及蛋白含量均显著高于阿托伐他汀组,但仍低于空白对照组（P〈0．05）。结论：阿托伐他汀可通过激活PPARβ／δ信号通路下调衰老心肌细胞TNF—d的表达。     

酒精性心肌病大鼠过氧化酶体增殖物激活受体α和类维甲酸受体α的表达以及肉毒碱干预

目的 探讨过氧化酶体增殖物激活受体(PPAR)α和类维甲酸受体(RXR)α在酒精性心肌病(ACM)中的表达以及肉毒碱干预疗效和可能机制.方法 雄性Wistar大鼠90只分为3组:酒精组、酒精+药物组和对照组.每组30只.6个月后使用免疫组化法检测心肌组织Ⅰ型胶原、Ⅲ型胶原、基质金属蛋白酶-9(MMP-9)和信号转导蛋白-3(Smad-3)的蛋白表达,Western blot法测定心肌组织PPARα和RXRα蛋白表达.结果 酒精组和酒精+药物组Ⅰ型胶原、Ⅲ型胶原、MMP-9和Smad-3蛋白表达显著高于对照组(P<0.01和0.05).PPARα和RXRα蛋白表达(酒精组分别为0.156和0.192,酒精+药物组分别为0.248和0.385)显著少于对照组(P<0.01和0.05).酒精组与酒精+药物组比较,Ⅰ型胶原、Ⅲ型胶原、MMP-9、Smad-3、PPARα和RXRα蛋白表达具有显著差异(P<0.05).PPARα和RXRα与左心室射血分数和左心室短轴缩短率呈显著正相关(P<0.01),与左心室舒张末期内径、Ⅰ型胶原、Ⅲ型胶原、MMP-9和Smad-3呈显著负相关(P<0.01).结论 酒精性心肌病进展中PPARα和RXRα蛋白表达下调,心脏重构和心肌纤维化形成.肉毒碱可能通过PPARα和RXRα代谢途径改善心脏重构和心肌纤维化.     

β受体亚型在人心房成纤维细胞增殖分泌中的作用

目的通过肾上腺素能受体激动剂和拮抗剂干预体外培养的人心房成纤维细胞,研究β受体在成纤维细胞增殖分泌中的作用及机制。方法：取体外循环患者右心耳组织行成纤维细胞分离培养、鉴定。实验分4组,对照组（CON组）、异丙肾上腺素组（ISO组）、ISO＋阿替洛尔组（ISO＋ATE组）、ISO＋卡维地洛组（ISO＋CAR组）;干预后检测上清液中羟脯氨酸含量、细胞增殖、β受体mRNA及pPKAR2蛋白的表达。结果：1,ISO＋CAR组和ISO组的细胞增殖率分别为11-3％和33．8％,P〈0．01;其上清液中羟脯氨酸含量分别为6．32±1．30“g／ml和8．68±1．80μg／ml,P〈0．01;2,D受体亚型mRNA的表达：p2AR／GAPDH在IsO＋CAR和ISO组分别为0．52和066,P〈0．0l;而ATE＋ISO组和ISO组分别为：0．63和0．66,P〉0．05。3,pPKA蛋白表达：ISO＋CAR组同ISO组相比,pPKAR2／D．actin分别是0．60和0．81,P〈0．01。结论：ISO能刺激体外培养的人心房成纤维细胞增殖和分泌胶原;非选择性B受体拮抗剂卡维地洛可抑制成纤维细胞增殖及分泌,其机制与D2AR-pPKAR2途径有关。     

过氧化物酶体增殖物激活受体γ 在应激致小鼠心肌损伤中的作用

目的探讨应激致小鼠心肌损伤中过氧化物酶体增殖物激活受体γ（PPARγ）的变化特征及吡格列酮的防护作用。方法 50只KM小鼠,完全随机分为5组,每组10只：对照组、力竭游泳运动组、噪声组、复合刺激组、吡格列酮干预组（药物组）。造模成功后,分别取血清和心肌组织,HE染色法观察心肌形态变化;ELISA检测法测定血清皮质酮（CORT）、肌钙蛋白I（TnI）和超氧化物歧化酶（SOD）含量;Real-time PCR检测心肌组织PPARγmRNA表达,Western blot检测心肌组织PPARγ的蛋白表达。结果 HE染色结果显示,各组小鼠心肌形态变化不明显。与对照组相比,三组应激源作用组血清CORT和TnI升高明显（CORT：106.75±33.96,96.43±20.63,173.17±22.28;TnI：0.113±0.032,0.077±0.034,0.133±0.041;P〈0.05）,SOD则显著下降（103.36±10.43,124.93±8.47,97.16±17.30）,心肌PPARγmRNA和蛋白水平明显降低（P〈0.05）。药物干预组与三组应激源作用组比较,血清CORT和TnI显著降低（P〈0.05）,SOD则显著升高,心肌PPARγmRNA和蛋白水平明显升高（P〈0.05）。结论应激可导致心肌微损伤;应激条件下,PPARγ在心肌的表达降低;吡格列酮干预可使应激导致的心肌微损伤得到有效防护。     

非诺贝特对胰岛素抵抗大鼠肝脏脂肪酸氧化的影响

目的观察自发胰岛素抵抗的OLETF大鼠肝脏脂肪酸氧化代谢的异常以及非诺贝特对其的影响。方法以8周龄LETO大鼠为正常对照,将同周龄OLETF大鼠随机分为未治疗组和治疗组[非诺贝特20ms／（kg·d）],于17周龄及30周龄分批处死动物,使用实时定量RT－PCR法测定肝脏组织脂肪酸氧化相关基因过氧化物酶体增生物激活受体－α（PPAR－α）、丙二酰辅酶A脱羧酶（MCD）、脂酰辅酶A氧化酶（AOX）mRNA的表达。结果与唧0大鼠相比,未治疗组8周龄大鼠首先出现糖负荷后2h游离脂肪酸（FFA）水平升高（P〈0．05）,17周龄出现空腹FFA以及血糖、胰岛素水平的升高;30周龄时肝脏组织PPAR-α、MCD、AOXmRNA表达均下调,甘油三酯含量升高（P均〈0．01）。治疗组空腹FFA水平明显降低,肝组织PPAR-α、MCD、AOXmRNA表达上调,肝组织甘油三酯含量下降（P均〈0．05）。结论非诺贝特可使OLETF大鼠肝脏脂肪含量下降,这可能与其降低血清FFA水平及上调肝脏组织与脂肪酸氧化相关酶的基因表达有关。     

Platelet and erythrocyte Mg2+, Ca2+, Na+, K+ and cell membrane adenosine triphosphatase activity in essential hypertension in blacks.

OBJECTIVE: To assess the relationship between intracellular Mg2+, Ca2+, Na+ and K+ and cell membrane adenosine triphosphatase (ATPase) activity in normotensive and hypertensive blacks. DESIGN: Intracellular cations and cell membrane ATPase activity were studied in black patients with untreated essential hypertension and age-, weight- and height-matched normotensive controls. Platelet, erythrocyte and serum Mg2+, Ca2+, Na+ and K+ levels as well as platelet and erythrocyte membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities were measured in all subjects. METHODS: Intracellular Na+ and K+ were measured by flame photometry and Mg+ and Ca+ by atomic absorption spectrophotometry. Cell membrane ATPase activity was determined by a colorimetric method. RESULTS: The hypertensive group consistently demonstrated depressed activity of each ATPase studied, with significantly lower serum Mg2+, serum K+, erythrocyte Mg2+ and platelet Mg2+ levels compared with the normotensive group. Platelet Na+ and Ca2+ and erythrocyte Ca2+ were significantly elevated in the hypertensive group. In the hypertensive group, mean arterial pressure (MAP) was inversely correlated with platelet and erythrocyte membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase. Serum Mg2+, serum Ca2+ and platelet Mg2+ were negatively correlated with MAP in the hypertensive group whilst erythrocyte and platelet Ca2+ were positively correlated. In the normotensive group, platelet Mg2+ and MAP were negatively, and erythrocyte Ca2+ and MAP, positively correlated. CONCLUSIONS: Black patients with essential hypertension have widespread depression of cell membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities with serum and intracellular Mg2+ depletion and cytosolic Na+ and Ca2+ overload, which may reflect an underlying membrane abnormality in essential hypertension. These cellular abnormalities may be related to the defective transport mechanisms that in turn may be aggravated by Mg2+ depletion.     

Beta-adrenergic receptors and calcium cycling proteins in non-failing, hypertrophied and failing human hearts: transition from hypertrophy to failure.

Left ventricular hypertrophy may lead to heart failure. The transition between hypertrophy and heart failure is, however, incompletely understood. On the cellular level, human heart failure is characterized by alterations in Ca(2+)-cycling proteins and beta-adrenergic receptor density, but the hypertrophied human heart remains largely under studied. In this investigation, 21 donor hearts which could not be used for transplantation were studied. Ten of these hearts came from organ donors with documented left ventricular hypertrophy and normal cardiac function. Eleven of the hearts were non-failing, obtained from individuals with no evidence of cardiac disease. Nine failing hearts from transplant recipients were also studied. beta-adrenergic receptor density was determined by radioligand binding. mRNA for atrial natriuretic factor, calsequestrin, sarcoplasmic reticulum Ca(2+)-ATPase, and phospholamban was measured by Northern blot. Actin, calsequestrin, sarcoplasmic reticulum Ca(2+)-ATPase, and phospholamban proteins were quantified by Western blot. In both hypertrophied and failing ventricles, mRNA for atrial natriuretic factor was expressed, as compared to no expression in non-failing hearts. In failing hearts, beta -adrenergic receptor density and both mRNA and protein levels of the Ca(2+)-ATPase were significantly decreased v non-failing hearts. By comparison, hypertrophied hearts showed a reduction in mRNA expression for both the Ca(2+)-ATPase and phospholamban with no change in the corresponding protein levels, and no change in beta-receptors. These data suggest that the previously demonstrated reduction in beta-adrenergic receptors and Ca(2+)-cycling proteins in the failing human heart may be features of the decompensated state, but are not found in human hearts with left ventricular hypertrophy and preserved systolic function.     

Diminished expression of sarcoplasmic reticulum Ca(2+)-ATPase and ryanodine sensitive Ca(2+)Channel mRNA in streptozotocin-induced diabetic rat heart

The diabetic heart has an abnormal intracellular calcium ([Ca(2+)]i) metabolism. However, the responsible molecular mechanisms are unclear. The present study aimed to investigate mRNAs expressed in the proteins which regulate heart [Ca(2+)]i metabolism in streptozotocin (STZ)-induced diabetic rats. Expression of sarcoplasmic reticulum Ca(2+)-adenosine triphosphatase (SR Ca(2+)-ATPase) mRNA was significantly less in the heart 3 weeks after STZ injection than that in the age-matched controls. Together with the down-regulation of SR Ca(2+)-ATPase, expression of ryanodine sensitive Ca(2+)channel (RYR) mRNA was also decreased 12 weeks after STZ injection. Insulin supplementation fully restored the decreased mRNAs expression of SR Ca(2+)-ATPase and RYR. The diminished expression and restoration with insulin supplementation of SR Ca(2+)-ATPase was further confirmed at the protein level. In contrast, expression of mRNAs coding the L-type Ca(2+)channel, Na(+)-Ca(2+)exchanger, or phospholamban were not affected 3 or 12 weeks after STZ injection. These results can be taken to indicate that the down-regulation of SR Ca(2+)-ATPase and RYR mRNAs is a possible underlying cause of cardiac dysfunction in STZ-induced diabetic rats.     

Heterogeneous transmural gene expression of calcium-handling proteins and natriuretic peptides in the failing human heart.

OBJECTIVE: Human heart failure is associated with a disturbed intracellular calcium (Ca2+) homeostasis. In this regard, ventricular wall stress is considered to be a determinant for expression of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a). In the present study, we analyzed the transmural protein and/or mRNA levels of SERCA2a, other Ca(2+)-handling proteins, and of atrial and brain natriuretic peptides (ANP and BNP) in the human heart. METHODS: Subepicardial (epi), midmyocardial (mid), and subendocardial (endo) sections of the left ventricular free wall from end-stage failing (n = 17) and nonfailing (n = 5) human hearts were analyzed by Western blot for immunoreactive protein levels of SERCA2a, phospholamban (PLN), and calsequestrin (CS). Subepi- and subendocardial sections were analyzed by Northern blot for steady-state mRNA levels of SERCA2a, Na(+)-Ca2+ exchanger (NCX1), ANP, and BNP. RESULTS: SERCA2a protein and mRNA levels were reduced by 40 +/- 5% (P < 0.01) and 25 +/- 7% (P < 0.05) in endo compared to epi in the failing heart and by 27 +/- 14% and 16 +/- 12% (non-significant) in the nonfailing heart, respectively. PLN protein levels were reduced by 23 +/- 6% (P < 0.05) in endo compared to epi in the failing heart and by 17 +/- 25% (non-significant) in the nonfailing heart, whereas CS protein levels and NCX1 mRNA levels were similar across the left ventricular wall. Strikingly, in the failing heart, both BNP and ANP mRNA levels were upregulated predominantly in endo. CONCLUSIONS: In the failing human heart, SERCA2a and PLN, as well as natriuretic peptides but not CS and NCX1 are differentially expressed across the left ventricular wall, implicating (1) different susceptibility of subendocardium and subepicardium to factors affecting expression of these proteins and (2) differences in regulation of the distinct calcium-cycling proteins.     

Synergistically Stimulated (Na+,K+)-Adenosine Triphosphatase from Plasma Membrane of a Marine Diatom

An ATP-hydrolyzing activity with the properties of a Mg(2+)-dependent (Na(+),K(+))-ATPase (ATP phosphohydrolase, EC 3.6.1.3) from a 20-fold purified plasma membrane fraction of the marine diatom, Nitzschia alba is described.The basal activity requires Mg(2+) and further stimulation by Na(+) or Na(+) plus K(+) is dependent on the presence of Mg(2+); Mn(2+) or Co(2+) can partially substitute for the divalent cation requirement but Ca(2+) equimolar with Mg(2+) inhibits the activity by 54%. ATP is the preferred substrate for the Na(+) plus K(+) stimulated activity, while CTP, UTP, and ADP are only slightly hydrolyzed. The apparent K(m) is 8 x 10(-4) M ATP.The ATP hydrolysis-rate is dependent on the relative concentrations of Na(+) and K(+); the K(0.5) for Na(+) and K(+) are 2 mM and 50 mM, respectively. Basal activity is synergistically stimulated by Na(+) plus K(+) only at certain ion concentrations and shows a strong specificity for both cations.In the presence of Na(+) at 5 mM and K(+) at 350 mM, the ATPase is completely inhibited by p-chloromercuric benzoic acid 10(-4) M, N-ethyl maleimide 10(-3) M, and iodoacetamide 10(-2) M, but is insensitive to ouabain at 10(-7) to 10(-3) M.This study demonstrates for the first time that algal plasma membrane contains an ATPase that is synergistically stimulated by Na(+) and K(+).     

Increased functional importance of the Na,Ca-exchanger in contracting failing human myocardium but unchanged activity in isolated vesicles

The present study aimed to investigate the hypothesis that the function of the Na,Ca-exchanger (NCX) is of higher importance for contractility and Ca(2+)-homeostasis in left ventricle from terminally failing than from nonfailing human hearts. The effect of decreasing extracellular [Na](e) (140 to 25 mmol/L) on force of contraction in isolated left ventricular papillary muscle strips was studied as a reflection of NCX function in multicellular preparations (terminally failing, DCM, dilated cardiomyopathy, NYHA IV, n = 13; nonfailing, NF, donor hearts, n = 10). Decreasing [Na](e) has previously been shown to increase contractility in vitro secondary to a decreased Ca(2+)-extrusion by the NCX. In addition, the NCX activity was measured as Na(+)-dependent (45)Ca(2+)-uptake into isolated myocardial vesicles as a function of time and Ca(2+)-concentration (DCM n = 8, NF n = 8). Decreasing [Na](e) enhanced the contractility of papillary muscle strips in both DCM and NF, but the contractility of DCM was increased at smaller reductions of [Na](e) than NF. The NCX activity in isolated myocardial vesicles was unchanged as a function of time (T(1/2): DCM 2.4 +/- 0.3 s versus NF 2.5 +/- 0.3 s) and as a function of Ca(2+) (DCM 0.99 +/- 0.08 versus NF 0.96 +/- 0.07 nmol/mg protein x 3 s, K(1/2): DCM 39.2 microM versus NF 38.3 microM). These results demonstrate a higher sensitivity of the failing human myocardium towards Na,Ca-exchanger mediated positive inotropic effects, suggesting a higher significance of the Na,Ca-exchanger for the extrusion of Ca(2+)-ions in intact failing versus nonfailing human myocardium. Since the activity and the Ca (2+)-affinity of the Na,Ca-exchanger in isolated vesicles was unchanged, we propose that alterations in Ca(2+)-and Na(+)-homeostasis (due to impaired function of the sarcoplasmic reticulum and the Na(+), K(+)-ATPase) or the prolonged action potential are the reason for this observation.     

Effect of dietary fats on erythrocyte membrane lipid composition and membrane-bound enzyme activities.

Four different oil-based diets were used in a feeding study involving rats to assess the relationship between the fatty acid composition of the dietary fat and its influence on erythrocyte membrane (EM) lipid composition and the activities of membrane-bound enzymes. Nutritionally adequate diets containing 20% groundnut (GNO), coconut (CO), safflower (SO), or mustard oil (MO) were fed to weanling CFY rats for 4 months. EMs were analyzed for total cholesterol, phospholipids, fatty acid profiles, and sialic acid content. Activities of membrane-bound enzymes such as Na+, K(+)-adenosine triphosphatase (ATPase), Mg(2+)-ATPase, Ca2+, Mg(2+)-ATPase, and acetylcholinesterase were also assayed. The activities of all membrane-bound enzymes, except Mg(2+)-ATPase, and sialic acid content were higher in the MO-fed group than in the rest of the groups. Ca2+, Mg(2+)-ATPase activity was distinctly lower in the SO-fed group than in the other groups. Cholesterol to phospholipid molar ratio was similar in all the groups. However, SO- and MO-fed groups displayed an increased cholesterol content and a higher degree of unsaturation in the membrane fatty acid composition. The higher membrane fatty acid unsaturation in the SO-fed group was principally due to linoleic (18:2) and arachidonic (20:4) acids, while in the MO-fed group it was mainly due to oleic (18:1), eicosenoic (20:1), erucic (22:1), and linoleic (18:2) acids. These results suggest a relationship between the quality of dietary fat, EM fatty acyl composition, and the activities of membrane-bound enzymes.     

Endoxin Antagonist Lessens Myocardial Ischemia Reperfusion Injury

OBJECTIVE: To elucidate whether endoxin is one of important factors involved in myocardial ischemia reperfusion (MIR) injury, the change of myocardial endoxin level was determined in rats with MIR injury model and the effects of anti-digoxin antiserum (ADA), an endoxin specific antagonist, on MIR injury were studied. METHODS: MIR injury model was obtained by ligating left anterior descending coronary artery 30 min followed by 45 min reperfusion. Sprague-Dawley rats were randomly divided into six groups of 10 rats, each. Sham group, MIR group, normal saline group, ADA 9, 18 and 36 mg.kg(-1). ECG was continuously recorded. After reperfusion left ventricular myocardium samples of ischemic area were processed immediately. Myocardial endoxin level, Na(+)-K(+)-ATPase, Ca(2+)-ATPase, Mg(2+)-ATPase activities, and intramitochondrial Ca(2+) content were measured. RESULTS: Myocardial endoxin level was significantly increased; Na(+)-K(+)-ATPase, Ca(2+)-ATPase, and Mg(2+)-ATPase activities were remarkably decreased; intramitochondrial Ca(2+) content was remarkably raised; ST segments of ECG were significantly elevated and occurrence and scores of ventricular arrhythmias were significantly increased in early stage of reperfusion in rats with MIR. In all groups with ADA, myocardial endoxin level was remarkably decreased; Na(+)-K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities were drastically increased; intramitochondrial Ca(2+) content was declined; ST segments and ventricular arrhythmias were improved. CONCLUSION: Myocardial endoxin level was increased in MIR, which implies that the elevated endoxin may be one of major factors inducing MIR injury. This postulate is supported by the observation that ADA has protective and therapeutic effects against MIR injury probably by antagonizing the action of endoxin. The underlying mechanism may be ascribed to restoration of energy metabolism, and attenuation of intracellular Ca(2+) overload.     

Characterization of a beta subunit of the gastric H+/K(+)-transporting ATPase

The catalytic subunit of the H+/K(+)-transporting ATPase (EC 3.6.1.3) has 62% identity to the alpha, or catalytic subunit, of the Na+/K(+)-transporting ATPase (EC 3.6.1.37); however, a homologous beta subunit was unknown until recently. Removal of the carbohydrate from purified hog H+/K(+)ATPase vesicles reveals a 35-kDa peptide that, when fragmented with protease V8, gives sequences homologous to both beta 1 and beta 2 subunits of the Na+/K(+)-ATPase. cDNA clones for a beta subunit of the gastric H+/K(+)-ATPase were isolated from a rabbit stomach cDNA library by using degenerate 17-mer oligonucleotide probes made to the protease V8-treated peptides. An open reading frame (54-926) encodes a predicted 291-amino acid peptide with Mr = 33,320, which exhibits 31% and 44% homologies to the Na+/K+)-ATPase beta 1 and Na+/K(+)-ATPase beta 2 proteins, respectively. A Kyte-Doolittle hydropathy plot predicts a single N-terminal transmembrane domain with a small hydrophobic region near the C terminus. The presumed extracytosolic domain contains seven potential N-linked glycosylation sites and six out of nine cysteines. Northern (RNA) blot analysis of stomach RNA with the rabbit H+/K(+)-ATPase beta probe identifies a single mRNA of 1.3-1.5 kilobases, similar in concentration to the alpha subunit mRNA. The presence of a defined gastric H+/K(+)-ATPase beta subunit extends the homology between H+/K(+)-ATPase and the Na+/K(+)-ATPase subclass of phosphoenzyme transport ATPases and distinguishes them from the monomeric Ca2+ and proton pump subclasses.     

Alterations of ion-dependent ATPase activities in the brain of Singi fish, Heteropneustes fossilis (Bloch), by triiodothyronine.

The activities of Na+K(+)- and Mg(2+)-ATPases in mitochondrial, microsomal, and cytosolic fractions of Singi fish (Heteropneustes fossilis Bloch) brain were investigated after injections of various doses (0.012, 0.025, 0.05, and 0.10 micrograms/g) of triiodothyronine (T3) for 3 consecutive days. Both ATPases were found in the mitochondrial and microsomal fractions. The cytosolic fraction showed only Mg(2+)-ATPase activity. Mitochondrial Na+K(+)-ATPase activity increased to almost the same level in fish treated with 0.025, 0.05, or 0.10 micrograms of T3/g, while the T3 dose of 0.012 micrograms/g was ineffective in this respect. Microsomal Na+K(+)-ATPase activity increased to about the same level with all of the doses of T3 used. No detectable amount of Na+K(+)-ATPase was found in the brain cytosolic fraction. Mitochondrial Mg(2+)-ATPase activity was enhanced with 0.025, 0.05, and 0.10 micrograms of T3/g. The last dose, however, produced a higher increase in activity than the other two doses. Surprisingly, microsomal and cytosolic Mg(2+)-ATPase activity was not increased by T3 treatment. Although T3 concentrations rose sharply after each T3 injection, the serum T3 level in T3-injected fish was not different from that in the control as observed on the fourth day. The T3-induced rise of Na+K(+)- and Mg(2+)-ATPase activities was inhibited by cycloheximide treatment. Immersion of Singi fishes in thiourea significantly reduced brain Na+K(+)-ATPase activity in microsomal and mitochondrial fractions but decreased Mg(2+)-ATPase activity only in the mitochondrial fraction. Three consecutive daily injections of T3 (0.10 micrograms/g) into the thiourea-treated fishes increased their ATPase activities even beyond the control level.(ABSTRACT TRUNCATED AT 250 WORDS)