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1Author    HorstW. AlterRequires cookie*
 Title    Permeability of Plasma Membrane Vesicles to Ouabain and Mg2+ as a Factor Determining Rate of Binding of Ouabain to Na+ and K+ Dependent ATPase  
 Abstract    N a+, K+-ATPase of the plasma membrane isolated from sheep kidney medulla exhibits functio­ nal asymmetry for the cardiac glycoside ouabain. In this vesicular membrane preparation the rate of binding o f ouabain was slow (time constant > 60 min) when the vesicles were incubated in the presence o f isotonic sucrose. Upon treatment o f the preparation with hypoosmotic shock or phos-pholipase A the initial rate of ouabain binding was enhanced at least 3 fold. In equilibrium a concentration of the ouabain-enzyme-complex was obtained which was about twofold that of the untreated vesicles. This result suggests two types o f ouabain binding sites with an approximate stoichiometry of 1 to 1. The stoichiometry seems to be maintained at high concentrations of ouabain where binding curves show a biphasic time course. Additional information about hetero­ geneity of binding sites comes through experiments in which the vesicles were treated with Mg2+ prior to the addition o f ouabain. A minor fraction of the binding sites were occupied by ouabain only after longtime incubation with Mg2+. 
  Reference    Z. Naturforsch. 34c, 1224 (1979); received July 13/August 18 1979 
  Published    1979 
  Keywords    N a+, K+-ATPase, Plasma Membrane Vesicles, Cardiac Glycoside, Magnesium, Tightness 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-1224.pdf 
 Identifier    ZNC-1979-34c-1224 
 Volume    34 
2Author    Stylianos Tsakiris3, Panagiota Kouniniotou-Krontiri3, KleopatraH. Schulpisb, JohnC. Stavridis3Requires cookie*
 Title    L-Phenylalanine Effect on Rat Brain Acetylcholinesterase and Na+,K+-ATPase  
 Abstract    The effect of different L-phenylalanine (Phe) concentrations (0 .1 -1 2 .1 m M) , on acetylcho­ linesterase (A C h E) and N a+,K +-ATPase activities of brain homogenate and pure enzymes, was investigated at 37 °C. A C h E and Na+,K +-ATPase activities were determined according to Ellman G. -6 1 3) respectively, after preincubation with Phe. A C h E activity in brain homogenate or in pure eel E.electricus enzyme showed a decrease, which reached up to 18% with concentrations of 0 .9 -1 2 .1 m M . Brain homogenate N a+,K +-A TPase activity showed an increase 1 6 -6 5 % with 0 .2 4 -0 .9 mM of Phe, while an activity increase of 6 0 -6 5 % appeared with 0 .9 -1 2 .1 mM of Phe. Pure en­ zyme activity (from porcine cerebral cortex) was not affected by high Phe concentrations, while it was increased by low concentrations. The above results suggest: a) A direct effect of Phe on A C h E , b) A direct effect of low Phe concentrations and an indirect effect of high ones on Na+,K +-ATPase. 
  Reference    Z. Naturforsch. 53c, 163 (1998); received September 22/D ecem ber 15 1997 
  Published    1998 
  Keywords    L-Phenylalanine, R at Brain, Acetylcholinesterase, N a+, K +-ATPase, Mg2+-ATPase 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0163.pdf 
 Identifier    ZNC-1998-53c-0163 
 Volume    53 
3Author    Stylianos Tsakiris, Panagoula Angelogianni, JohnC. StavridisRequires cookie*
 Title    Effect of Aging on the Activities of Acetylcholinesterase, Na+, K+-ATPase and Mg2+-ATPase in Rat Pituitary and Hypothalamus  
 Abstract    Acetylcholinesterase (A C h E), N a+, K +-ATPase and Mg2+-A TPase activities were esti­ mated in homogenised rat pituitary and hypothalamus of 4-and 22-month-old rats. A C hE activity was not altered in the pituitary of aged com pared to adult rats, while it was found decreased by about 40% in the hypothalamus. N a+,K +-A TPase activity remained stable in the hypothalamus, while it was decreased by about 38% in the pituitary. Mg2+-A TPase activ­ ity remained unchanged in the hypothalamus, but was increased by about 83% in the pitu­ itary. This pituitary N a+, K +-ATPase inactivation may result in pathological mood and de­ creased neural excitability and metabolic energy production in aged animals.The age-related alterations of A C h E , Na+, K +-ATPase and Mg2+-A TPase activities may reflect changes in secretion and responses of some hormones of pituitary and hypothalamus. 
  Reference    Z. Naturforsch. 53c, 168 (1998); received O ctober 13/O ctober 31 1997 
  Published    1998 
  Keywords    Aging, R at Pituitary, Rat Hypothalamus, Acetylcholinesterase, N a+, K +-ATPase, Mg2+-ATPase 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0168.pdf 
 Identifier    ZNC-1998-53c-0168 
 Volume    53 
4Author    Stylianos Tsakiris3, Panagoula Angelogianni3, KleopatraH. Schulpisb, Panagiotis Behrakis3Requires cookie*
 Title    Protective Effect of L-Cysteine and Glutathione on Rat Brain Na+,K+-ATPase Inhibition Induced by Free Radicals  
 Abstract    The aim of this study was to investigate whether the preincubation of brain homogenates with L-phenylalanine (Phe), L-cysteine (Cys) or reduced glutathione (G SH) could reverse the free radical effects on N a+,K+-ATPase activity. Two well established systems were used for the production of free radicals: 1) F e S 0 4 (84 ^i m) plus ascorbic acid (400 |o.m) and 2) F e S 0 4, ascorbic acid and H20 2 (1 mM) for 10 min at 37 °C in hom ogenates o f adult rat whole brain. Changes in brain N a+,K+-ATPase activity and total antioxidant status (TAS) were studied in the presence of each system separately, with or without Phe, Cys or GSH. TAS value reflects the amount of free radicals and the capacity of the antioxidant enzymes to limit the free radicals in the homogenate. N a+,K+-ATPase was inhibited by 35 -5 0 % and TAS value was decreased by 5 0 -6 0 % by both systems of free radical production. The enzy­ matic inhibition was completely reversed and TAS value increased by 150-180% when brain homogenates were preincubated with 0.83 mM Cys or GSH. However, this N a+,K+-ATPase inhibition was not affected by 1.80 m M Phe, which produced a 4 5 -5 0 % increase in TAS value. It is suggested that the antioxidant action of Cys and GSH may be due to the binding of free radicals to sulfhydryl groups of the m olecule, so that free radicals cannot induce N a+,K+-ATPase inhibition. Moreover, Cys and GSH could regulate towards normal values the neural excitability and metabolic energy production, which may be disturbed by free radical action on N a+,K+-ATPase. 
  Reference    Z. Naturforsch. 55c, 271—2 (2000); received October 8/Decem ber 21 1999 
  Published    2000 
  Keywords    L-Cysteine, Reduced Glutathione, L-Phenylalanine, Free Radicals, N a+, K+-ATPase 
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 TEI-XML for    default:Reihe_C/55/ZNC-2000-55c-0271.pdf 
 Identifier    ZNC-2000-55c-0271 
 Volume    55