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.     

Blockade of voltage-dependent and Ca2+-dependent K+ current components by internal Ba2+ in molluscan pacemaker neurons

Summary Internal Ba²⁺ blocks both the Ca-dependent component, as well as the voltage-dependent component of the K⁺ current in molluscan pacemaker neurons.     

Zur biologischen Bedeutung von Fe3+ und Cu2+ als Komplexbildner

Summary The possible role of the metabolism of heavy metal ions in the process of ageing is discussed. It is suggested that, during this process, Cu²⁺ and Fe³⁺ as strong complexing ions, inhibit the activity of other metal enzymes by replacing their metal ion-activator. The relative stability of Cu²⁺- and Fe³⁺-complexes with various chelating compounds related to biological systems has been determined.     

Response of briefly glycerinated smooth muscle to Ca2+ and Mg2+

Summary Smooth muscle, treated with 50% glycerol solution at 27°C for 20 min, contracted on the application of Ca²⁺ or Mg²⁺. The briefly glycerinated smooth muscle can be used as a model system of smooth muscle contraction.     

Asymmetrical activation by Ca2+ of the erythrocyte membrane K+-dependent phosphatase

Resumen Los sitios con los cuales se combinan el ion Ca y el ATP para activar la fracción dependiente, ce K⁺ de la fosfatasa de la membrana del glóbulo rojo, están ubicados en la superficie interna de dicha membrana. Esta característica de asimetría, favorece la idea de la relación de esta enzima con la ATPase activada por Ca²⁺ de la membrana del glóbulo rojo.

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This work was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Argentina, and the Facultad de Farmacia y Bioquímica. A.F.R. and P.J.G. are established investigators from the CONICET.     

Extracellular Ca2+ and Mg2+ and cellular metabolism of phospholipids.

High extracellular concentration of Ca2+ inhibits the incorporation of 32P into the cellular phospholipids. This effect is more significant in neoplastic than in normal cells, and it is accompanied by an increase of the percentual incorporation into the lecithin fraction.     

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.     

Effects of Ca2+ and Mg2+ on motility of sea urchin spermatozoa

Summary Swimming speed of sea urchin spermatozoa, measured by a light scattering technique, did not change with 0-20 mM Ca²⁺ in the medium. The speed was maximum at the normal concentration of Mg²⁺ (49 mM) in sea water.Supported by grants-in-aid from the Ministry of Education, Science and Culture, Japan, and a grant from the Ford Foundation.     

Effects of Mn2+ and Mg2+ on the pigeon liver pyruvate kinase

Riassunto Mn²⁺ and Mg²⁺ attivano la piruvato cinasi di fegato di piccione in maniera distinta. In presenza di basse concentrationi di fosfoenolpiruvato Mn⁺ é piú efficace di Mg²⁺ ed é attivatore dell'enzima saturato da Mg²⁺. Piruvato cinasi (EC 2.7.1.40).

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This work was supported by a grant from the Consiglio Nazionale delle Ricerche, Roma, Italia.Silvia Baldi is a fellow of the Italian C.N.R.     

A histochemical demonstration of the Na+ + K+-ATPase activity in the thyroid and the effect of cyclic adenosine monophosphate (c-AMP).

With a suitable modification of the Farquhar and Palade technique the Na+ + K+-ATPase activity in guinea-pig thyroid is demonstrated. The addition of c-AMP (5 X 10(-6) M or 1.5 X 10(-5) M) to the incubation media produced an apparent intensification of the Na+ + K+ -ATPase activity in the thyroid.