Effect of Na+, K(+)-ATPase modifiers on high-affinity ouabain binding determined by quantitative autoradiography.
There is growing evidence on the existence of endogenous ouabain-like factors that modulate Na+, K(+)-ATPase activity. In this laboratory, two soluble subfractions (peaks I and II) were previously separated from rat cerebral cortex, which had opposite effects on Na+, K(+)-ATPase activity. Peak I stimulated and peak II inhibited the enzyme (Rodríguez de Lores Arnaiz and Antonelli de Gómez de Lima, Neurochem Res 11:933-947, 1986). The same effects are now reported for K(+)-p-nitrophenyphosphatase activity. Localization of high-affinity ouabain binding in rat brain was done by quantitative autoradiography using a microcomputer digital imaging system. Peak I did not modify, whereas peak II blocked ouabain binding in areas 3-4 of cerebral cortex, dentate gyrus, stria terminalis, thalamic nuclei, and basal ganglia. Similar results were obtained when ouabain binding was determined in rabbit cerebral cortex and by a conventional filtration assay in nerve ending membranes obtained from rat cerebral cortex. These results favour the idea that the factor present in peak II fraction might behave as an ouabain-like substance.
Antonelli
M
M
Instituto de Biología Celular, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Casillas
T
T
Rodríguez de Lores Arnaiz
G
G
D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors*; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000201:enzymology*; D001923:Brain Chemistry; D010042:Ouabain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology*; D014020:Tissue Extracts / Q000494:pharmacology
D014020:Tissue Extracts; D010042:Ouabain; D009597:4-Nitrophenylphosphatase; D000254:Sodium-Potassium-Exchanging ATPase