SODIUM-POTASSIUM-ACTIVATED ATPase AND POTASSIUM-ACTIVATED p-NITROPHENYLPHOSPHATASE: A COMPARISON OF THEIR SUBCELLULAR LOCALIZATIONS IN RAT BRAIN

R. W. ALBERS; G. RODRÍGUEZ DE LORES ARNAIZ; E. DE ROBERTIS

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 1965 vol. 53 p. 557 - 564

0027-8424

SODIUM-POTASSIUM-ACTIVA TED A TPase ANDPOTASSIUM-ACTIVA TED p-NITROPHENYLPHOSPHA TASE:A COMPARISON OF THEIR SUBCELLULAR LOCALIZATIONSIN RAT BRAIN*BY R. W. ALBERS,t GEORGINA RODRIGUEZ DE LORES ARNAIZ, ANDE. DE ROBERTISINSTITUTO DE ANATOMIA GENERAL Y EMBRIOLOGIA, FACULTAD DE CIENCIAS MEDICAS,BUENOS AIRES, ARGENTINACommunicated by Seymour S. Kety, January 27, 1965The association of a Na+-K+-activated ATPase (ATP phosphohydrolase, EC.3.6.1.4.) with the active transport of these cations is supported by substantial evidence.1-4 An effect of sodium ions on a brain ATPase was first reported by Utter.5 Further work has led to the concept that the Na+-K+-ATPase activity may be a resultant of transphosphorylations within the cell membrane which could couple phosphate bond energy directly to cation transport.6-8 Consequently, the enzyme system would be an integral component of specialized membranes. Several workers have suggested that the final step in the ATPase reaction sequence may involve a K+-activated phosphatase6' 9 and in particular, a phosphoprotein phosphatase. Since phenyl phosphate serves as substrate for some phosphoprotein phosphatases'0 and a K+-activated p-nitrophenylphosphatase occurs in brain,'1 the structural association of a K+-activated phosphatase with the Na+-K+-ATPase in well-defined subcellular units would support their possible functional relationship.However, the operationally defined subcellular fractions of brain as prepared invarious laboratories have produced discordant accounts of ATPase localizations:Deul and McIlwain'2 found Na+-activated ATPase mainly in cerebral microsomes;Schwartz et al.'3 found 75 per cent of the Na+-activated ATPase associated withmicrosomal material other than ribosomes; Jiimefelt'4 studied brain homogenatesin 0.25 M sucrose in which the major ATPase activity was found in a heavy microsomal fraction recovered after centrifuging at 25,000 g X 45 min. In a more recent paper by Hayashi et al.,'5 a large percentage of activity was found in a nuclear fraction containing cell debris and intact cells and also in the mitochondrial and microsomal fractions.The aim of the present work has been that of studying the Na+-K+-ATPase in aseries of brain fractions which havepreviously been characterized by electron microscopy and a series of biochemical parameters. The methods of cell fractionationused in this laboratory permit the isolation of several subcellular fractions of mammalian brain. Nuclei, myelin, nerve endings (synaptic complexes), and microsomes can be separated and their submicroscopic structure studied. Refinements in these techniques have also led to the isolation of two populations of nerve endings and to the dismantlement of the synaptic complex with separation of synaptic vesicles from mitochondria, axoplasm, and most of the membranes.