title: Comparison between fluxes of potassium and of chloride in astrocytes in primary cultures.
abstract: Transport processes operating in astrocytes were examined by measuring unidirectional fluxes of 42K and 36Cl in primary cultures of mouse astrocytes, at steady-state with respect to ion composition. The total K+ uptake rate was 2025 nmol X mg-1 protein X min-1. This rate was not influenced by furosemide (2 mM), an inhibitor of Cl- uptake and K+-K+ exchange, or acetazolamide (0.1 mM), a carbonic anhydrase inhibitor. Ouabain (1 mM) inhibited the uptake rate by 541 nmol X mg-1 X min-1. The equilibrated K+ content was determined to be 696 nmol X mg-1. The rate constant for efflux was 2.76 min-1. This equals an efflux rate of 1921 nmol X mg-1 X min-1, i.e. a similar value as the influx. Furosemide and ouabain did not inhibit the efflux. The equilibrated Cl- content was found to be 167 nmol X mg-1 and it decreased in furosemide-treated cells to 68.1 nmol X mg-1. The total Cl- uptake was 35 nmol X mg-1 X min-1 and it was inhibited by furosemide or bumetanide by 27 nmol X mg-1 X min-1. The mean resting membrane potential was found to be -77.4 mV. From these data we conclude: (1) that the K+ uptake rates are high, as can be expected from estimates based on literature data for K+ conductance in mammalian glial cells in situ; and (2) that the cells possess a very low relative Cl- permeability.
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001921:Brain / Q000166:cytology; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D009115:Muridae; D011188:Potassium / Q000378:metabolism*
chemical_list: D002712:Chlorides; D007473:Ion Channels; D011188:Potassium