MOVEMENTS OF CALCIUM AND OTHER CATIONS IN ISOLATED CEREBRAL TISSUES1

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Abstract
Abstract— Slices of guinea pig cerebral cortex were incubated in bicarbonate‐ or trisbuffered media. Influx of 45Ca2 +, 54Mn2 +, 133Ba2+ or 90Sr2+ was determined at intervals following addition of the cardiac glycoside, ouabain, to the medium. After incubation for 30 min in the presence of 45Ca2+ and in the absence of ouabain, about 40 per cent of the slice calcium became labelled. Ouabain (01 I″M) markedly increased 45Ca2 + content, as well as the content of unlabelled Ca2 +. Mg2+ and Na+ levels also rose while K+ content dropped at a more rapid rate. Ouabain also brought about increased uptake of 90Sr2+, 133Ba2 + and 54Mn2 +. Lowering the Na+ content of the media prevented the effects of ouabain and brought about an increase in calcium content of brain slices. Addition of 2,4‐dinitrophenol (01 mM) or iodoacetate (1 miu) had slight or moderate effects on 45Ca2+ uptake. The data are most compatible with the presence in cerebral tissue of a sodium‐calcium exchange process.