title: Effects of increased extracellular K on the elemental composition and water content of neuron and glial cells in leech CNS.
abstract: Elemental (Na, Cl, K) and water contents of leech (Macrobdella decora) neurons and glial cells were determined under steady-state exposure to 4, 10, and 20 mM KCl concentrations (bathing media) using x-ray microanalysis for quantitative digital imaging of frozen hydrated and dried cryosections. Effects of furosemide, 5-hydroxytryptamine (5-HT), and ouabain on elemental distribution changes, induced by exposure to 20 mM K, were also determined. Results demonstrated that packet glial cells and neurons accumulated substantial amounts of K that appeared evenly distributed throughout the cytoplasm. Cell water content also increased as a function of increased cytoplasmic K so that the net effect was an unchanged wet-weight K concentration (expressed as millimoles per kilogram wet weight). Dry-weight Na and Cl concentration (expressed as millimoles per kilogram dry weight) increased slightly in glial cells; however, because cell water increased, both Na and Cl (wet-weight) concentrations decreased. Neurons, in contrast, had no significant change in either Na or K on a wet-weight basis, so a relatively constant Na/K ratio was maintained despite a small, but significant, increase in K (dry weight) and cell water. These increases, like those in packet glia, were a function of exposure to different concentrations of extracellular space K. These changes were completely abolished by 10(-4) M ouabain. Neither furosemide nor 5-HT appeared to affect neuronal or glial K wet-weight concentrations. These data show that both glial cells and neurons can act as substantial reservoirs for K while maintaining stable K concentrations (by altering cell water content and elemental composition). This process appears to depend on a functioning Na+, K+-ATPase system.
authors.affiliation: Department of Anesthesiology, University of Texas Medical School, Houston, Texas.
authors.forename: A J
authors.initials: AJ
authors.lastname: Saubermann
authors.forename: J D
authors.initials: JD
authors.lastname: Stockton
mesh_terms: D000818:Animals; D002712:Chlorides / Q000378:metabolism; D004573:Electrolytes / Q000378:metabolism*; D004577:Electron Probe Microanalysis; D005110:Extracellular Space / Q000378:metabolism; D005665:Furosemide / Q000494:pharmacology; D007865:Leeches / Q000378:metabolism*; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D014867:Water / Q000378:metabolism*
chemical_list: D002712:Chlorides; D004573:Electrolytes; D014867:Water; D012701:Serotonin; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D011188:Potassium