Effect of Na+, K+ ATPase modifiers on high affinity ouabain binding determined by quantitative autoradiography

M. ANTONELLI; T. CASILLAS ; G. RODRÍGUEZ DE LORES ARNAIZ

JOURNAL OF NEUROSCIENCE RESEARCH

WILEY-LISS, DIV JOHN WILEY & SONS INC

Año: 1991 vol. 28 p. 324 - 331

0360-4012

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.