Reversal by lecithin of the amobarbital-induced inhibition of microsomal (Na+K)-activated ATPase

Résumé L'amobarbital de soude inhibe l'activité du (Na+K)-ATPase du réticule sarcoplasmique isolé. Cette inhibition peut être évitée par l'addition de lécithine purifiée. La lécithine pré-incubée en présence de l'amobarbital inhibe (Na+K)-ATPase.     

Solubilization and purification of Na+-K+ ATPase of human erythrocyte mambranes using sodium deoxycholate]

The (Na+-K+)-dependant ATPase prepared from human erythrocyte ghosts has been purified with sodium deoxycholate in a high ionic medium. After the purification, 60% of the native activity bound to the membranes was recovered.     

Effects of EDTA on (Na+-K+) ATPase bound to human erythrocyte membranes]

Membranes preincubation with high EDTA concentration induced an alteration on (Na"-K+) ATPase kinetic behaviour. This effect can be related to a change in calcium content tightly bound to the membranes.     

The effect of temperature on the ouabain-sensitivity of Na+−K+-activated ATPase and fluid secretion by the Malpighian tubules ofLocusta

Summary Temperature markedly affected the ouabain-sensitivity of both the Na⁺–K⁺-activated ATPase activity and the secretion of fluid by the Malpighian tubules ofLocusta. Varying the K⁺ concentration in the bathing medium did not affect the ouabain-sensitivity of the fluid secretory process.     

Postnatal decline of (Ca2+ + Mg2+)-activated membrane ATPase in cattle red cells.

Acitivity of membrane bound (Ca2+ + Mg2+)-stimulated ATPase, associated with Ca2+ outward transport, in calf red cells is high at birth and declines with a rate constant of 0.041 d-1 after the 3rd week. The decline parallels the disappearance of fetal hemoglobin.     

Effects of inhibition and stimulation of Na+-K+ active transport on the resting membrane input conductance of the guinea-pig ventricle

The effects of inhibition by ouabain and stimulation by high frequency drive of the sarcolemmal Na+-K+ active transport system on the resting input conductance (gi) of guinea-pig ventricular muscles were determined. Although both pump inhibition and stimulation were associated with changes in electrophysiological properties of the muscles, neither had a significant effect on gi.     

Inhibition of microsomal Na+ K+ ATPase of the brain by extracts of Mansonia altissima]

Water extracts of the bark of Mansonia altissima var altissima inhibit the activity of the Na+, K+-ATPase of Rabbit brain microsomes. The kinetics of hydrolysis of ATP show non-competitive inhibition analogous to that produced by ouabain.     

The role of distinct membrane components of the enzyme in the ouabain sensitivity of Na+/K+ ATPase]

Purified plasma membranes from a cell line derived from the murine plasmocytoma MOPC 173 exhibited a 50% inhibition of the Na+K+ ATPase by 120 muM ouabain. EDTA treatment of such membranes induced a drop in the ouabain concentration needed for 50% inhibition to 0.4 muM. Supernatants obtained after EDTA treatment were able to complement with Ca(++) + Mg++ the washed EDTA treated membranes which recover their original resistance.     

Na+-K+-aktivierbares Adenosintriphosphatase-system: Die Wirkung von Triton-X-100 auf die SH-Gruppen

Summary A significant portion of the SH-groups of the rat-brain Na⁺-K⁺-ATPase preparation is masked; it can be unmasked by the treatment of Triton-X-100. The inhibitory effects of PCMB and NEM on the ATPase activity are different in the detergent-treated and untreated preparations.     

Die Reversibilität der Wirkung von Digitoxin,Strophanthidin und Strophanthidin-3-bromazetat am Papillarmuskel und einer mikrosomalen Na+-K+-aktivierbaren ATPase des Meerschweinchens

Summary The reversibility of the inhibitory action of strophanthidin, strophanthidin-3-bromoacetate, and digitoxin on the Na⁺-K⁺-ATPase activity (microsomal fraction, guinea-pig brain) was compared with the rate of decline of their positive inotropic effects (papillary muscle, guinea-pig heart) after exposure to drug-free solution. The actions of strophanthidin and digitoxin were easily reduced on both systems. Strophanthidin-3-bromoacetate, however, was found to have an irreversible blocking effect on the transport ATPase, whereas its inotropic action could be rapidly abolished.

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Teilergebnisse der Dissertation von U.Fricke, Mainz.     

Norepinephrine-sensitive Na+/K+ ATPase activity in brown adipose tissue

Zusammenfassung Norepinephrin fördert in vitro die Tätigkeit einer Ouabain empfindlichen Na⁺/K⁺ ATPase. Diese Wirkung, durch eine geringe Dosis eines-adrenergischen Antagonisten eingeschränkt, scheint offenbar von einer 3,5-zyklischen AMP unabhängig zu sein. Die Tätigkeit der Brenzkatechin-induzierten ATPase stimmt mit der Auffassung überein, dass im aktivierten braunen Fettgewebe der Energieumsatz zusammen mit dem vermehrten Sauerstoffverbrauch ansteigt.

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Supported in part by research grants NASA No. NGR-05-004-035 and USPHS No. HD-03268. P.A.H. is a PHS predoctoral fellow (No. 1-GM-33, 505-04). A preliminary report of this work was presented at the 1969 Fall meeting of the Am. Physiol. Society; an abstract of this talk is contained in The Physiologist12, 257 (1969). We thank J. F.Detrick for his technical assistance.