POTASSIUM-INDUCED STIMULATION OF OXIDATIVE-METABOLISM OF GLUCOSE IN CULTURES OF INTACT CEREBELLAR GRANULE CELLS BUT NOT IN CORRESPONDING CELLS WITH DENDRITIC DEGENERATION

Production of (CO2)-C-14 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 physiologlcal potassium concentration (5 mM) or an elevated extracellular potassium concentration. During exposure to the normal extracellular potassium concentration, the rate of CO2 production in the two types of culture was identical. In the conventional granule cell cultures, the CO2 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, CO2 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.