METABOLISM OF ACETATE IN RAT-BRAIN NEURONS, ASTROCYTES AND COCULTURES- METABOLIC INTERACTIONS BETWEEN NEURONS AND GLIA CELLS, MONITORED BYNMR-SPECTROSCOPY

The existence of metabolic compartmentation is generally accepted for the brain because of the specific differences in glial and neuronal me tabolism. Extracellularly supplied acetate is believed to serve as a s ubstrate only for glia cells, but not for neurons. To further test thi s hypothesis, primary rat brain cultures of neurons, astrocytes, and c ocultures of both cell types were used to investigate the metabolic fa te of [2-C-13]acetate by means of nuclear magnetic resonance (NMR) spe ctroscopy. Acetate was metabolized by both cell types, neurons and ast rocytes in culture. While glutamine was the main product of glial meta bolism, labelled glutamate and aspartate were detected in neuron cultu res. Astrocytes and neurons in cocultures showed a very different pict ure, which is similar to results obtained from brain slices, or in viv o studies. The analysis of the isotopomer pattern of glutamate and glu tamine confirm an active glutamate-glutamine-cycle between neurons and astrocytes in cocultures. Furthermore, the analysis of unlabelled met abolites revealed a metabolic coupling of hypotaurine and taurine meta bolism in astrocytes and neurons, which provides both cell types with one of the most important organic osmolytes.