Astrocytes are morphologically heterogenous group of cells in central nervous system that maintain brain homeostasis. Neurons depend energetically on astrocytes, which are responsible for the glucose uptake from the bloodstream and synthesis of glycogen. Glucose or glucosyl units from glycogen enter glycolysis and derive lactate, the key energy source used by neurons. If the glucose supply from the bloodstream is not sufficient, lactate is transported from astrocytes to neurons via monocarboxylate transporters. Stimulation of adrenergic receptors stimulates glycolysis via cAMP signal pathway. In our experiments, we used Förster Resonance Energy Transfer, a highly sensitive microscopy technique used for measuring physiological processes. For monitoring the changes in lactate concentration ([lactate]i) we used a genetically encoded nanosensor Laconic, and for monitoring changes in pHi we used the reagent pHrodoTMGreen. We compared glucose metabolism in two astrocytic morphotypes (polygonal and stellate in vivo-like morphology) cultivated according to two different protocols using different media composition (addition of fetal bovine serum or HB-EGF). Adrenergic stimulation evoked similar responses in both morphotypes. Intense brain activity leads to high intracellular production of lactate, which may acidify the cytosol. We investigated how pHi changes if astrocytes are exposed to various lactate concentration. Extracellular application of lactate in low concentration (5 mM) induced a drop in pHi, which, in the time of monitoring, was recovered to the baseline value. On the other hand, applying lactate in high concentration (20 mM) caused cells not being able to recover pH value to the baseline in the time of monitoring.
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