Role of tropomyosin in the sensitivity of (Na+ + K+) ATPase to ouabain]

EDTA treatment of isolated plasma membranes from MF2S cells increased 1,000 fold the sensitivity of (Na+ + K+) ATPase activity to ouabain. The original sensitivity of the enzyme to the drug is recovered after addition of tropomyosin together with Ca++ ions to the treated membranes.     

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.     

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.     

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.     

Intracellular phosphate release by the Na+-K+-activated membrane ATPase

Zusammenfassung An menschlichen Erythrocyten hemmt Phloretin den passiven Austritt von anorganischem Phosphat. Mit Hilfe dieser Wirkung konnte gezeigt werden, dass die Na⁺-K⁺-aktivierte ATPase anorganisches Phosphat nicht direkt nach aussen befördert, sondern im Innern der Zelle freisetzt.     

The (Na++K+)-ATPase activity in brain of quaking mice

Summary The (Na⁺+K⁺)- and Mg²⁺-dependent ATPase distribution in several brain areas has been investigated in Quaking mutant mice characterized by myelin deficiency. A marked decrease of (Na⁺+K⁺)-ATPase activity has been found in limbic structures, hypothalamus and cerebellum. The Mg²⁺-dependent activity did not change. A possible involvement of the impairment of the (Na⁺+K⁺)-ATPase activity in the seizure susceptibility of this mice is discussed.Chargée de Recherche au CNRS.     

Distribution of (Na++K+)-ATPase in the hindgut ofGlossina morsitans morsitans Westwood

Summary (Na⁺+K⁺)-ATPase activity was higher in preparations from the ileum ofGlossina mortisans than in those from the rectum. This result suggests that the ileum as well as the rectum, may play a role in osmoregulation in the tsetse fly.     

Phospholipid composition of cardiac (Na++K+)-ATPases from various species

Summary There is a difference in phospholipid composition of cardiac (Na⁺+K⁺)-ATPase preparations between species which are sensitive to ouabain and those which are not. Sphingomyelin is higher and phosphatidylcholine is lower in the enzymes from sensitive species than in those from insensitive ones. Lysophosphatidylcholine is detectable only in the latter preparations.     

Regulation of rat renal (Na++K+)-adenosine triphosphatase mRNA levels by corticosterone

We investigated the mechanisms for glucocorticoid regulation of rat renal NaK-ATPase activity. Our findings suggest that the magnitudes of corticosterone-induced increases in ₁ mRNA and ₁ mRNA levels are similar in the kidney of the adult adrenalectomized rats. The results also suggest that corticosterone restores NaK-ATPase activity in adrenalectomized rats prior to any enhanced sodium delivery.     

The (Na+ + K+)-ATPase activity in brain of Quaking mice.

The (Na+ 4 K+)- and Mg2+-dependent ATPase distribution in several brain areas has been investigated in Quaking mutant mice characterized by myelin deficiency. A marked decrease of (Na+ + K+)-ATPase activity has been found in limbic structures, hypothalamus and cerebellum. The Mg2+-dependent activity did not change. A possible involvement of the impairment of the (Na+ + K+)-ATPase activity in the seizure susceptibility of this mice is discussed.     

Effect of cholesterol oxidation on (Na+, K+) ATPase activity of erythrocyte membranes

Summary By incubation of human erythrocyte ghosts with cholesterol oxidase (EC 1.1.3.6) part of the cholesterol of the membrane is replaced by 4-cholesten-3-one. This alteration in the sterol composition is accompanied by an inhibition of the (Na⁺, K⁺) ATPase of the erythrocyte membrane.Acknowledgments. This study was supported by the Deutsche Forschungsgemeinschaft Bonn-Bad Godesberg and the Sonderforschungsbereich 90 of the University of Heidelberg. We thank Mr.J. Schmidt and MissI. Geldmacher for skilful technical assistance.     

Phospholipid composition of cardiac (Na+ + K+)-ATPases from various species

There is a difference in phospholipid composition of cardiac (Na+ + K+)-ATPase preparations between species which are sensitive to ouabain and those which are not. Sphingomyelin is higher and phosphatidylcholine is lower in the enzymes from sensitive species than in those from insensitive ones. Lysophosphatidylcholine is detectable only in the latter preparations.     

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.     

The effect of physostigmine on (Na++K+)-ATPase activity in different rat brain regions

Summary The activity of (Na⁺+K⁺)-ATPase and acetylcholine esterase were folloed in rat brain cerebral cortex, caudate, thalamus, hippocampus and medulla after i.v. administration of physostigmine. Both enzymes were found to be inhibited in a dose-dependent manner. The most pronounced inhibition of (Na⁺+K⁺)-ATPase was found in caudate. where the highest activity of acetylcholine esterase is found.These studies were supported by a grant from the Union of Science of Republic Serbia, No. 40404-14.