Potassium-induced stimulation of oxidative metabolism of glucose in cultures of intact cerebellar granule cells but not in corresponding cells with dendritic degeneration

Abstract

Production of 14CO 2 from uniformly labelled glucose was measured in conventional cultures of mouse cerebellar granule cells (a glutamatergic cell type) and in corresponding cultures which had been grown in such a manner that they showed massive degeneration of dendrites, but were otherwise morphologically normal. Both kind of cultures were studied during exposure to either a physiological potassium concentration (5 mM) or an elevated extracellular potassium concentration. During exposure to the normal extracellular potassium concentration, the rate of CO 2 production in the two types of culture was identical. In the conventional granule cell cultures, the CO 2 production showed a rectilinear increase as a function of the extracellular potassium concentration from 5–100 mM; this stimulation was abolished by ouabain, a specific inhibitor of Na +, K +-ATPase. In granule cells showing dendritic degeneration, CO 2 production increased only slightly at extracellular potassium concentrations of 25–100 mM. These findings suggest that the metabolic stimulation in morphologically intact cells may be the result of a depolarization-induced sodium uptake, which has a mainly or exclusively dendritic localization, and secondarily leads to a stimulation of the Na +, K +-ATPase at its intracellular sodium-sensitive site.