Extracellular N-methyl-D-glucamine leads to loss of hair-cell sodium, potassium, and chloride.
The organic cation N-methyl-D-glucamine (NMDG) is often used to replace extracellular sodium in experimental studies. Replacing 100 mM of Na+ with NMDG+ in the fluid bathing isolated goldfish hair cells led to a rapid loss not only of cell sodium, but also of cell potassium and chloride. The loss of inorganic cell solutes was accompanied by acidification of the cells. Cell volume did not change significantly. These results are consistent with passage of the cationic form of NMDG, a titratable amine with a pKa of 9.6, across the hair-cell membrane. These results should have bearing in interpreting results of experiments in which this cation is used to replace extracellular sodium, particularly for periods of time longer than 3 min.
Mroz
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Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston 02114.
Lechene
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D000818:Animals; D048429:Cell Size; D002712:Chlorides / Q000378:metabolism*; D004577:Electron Probe Microanalysis; D006054:Goldfish; D006198:Hair Cells, Auditory / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D017136:Ion Transport; D008536:Meglumine / Q000494:pharmacology*; D009994:Osmolar Concentration; D010758:Phosphorus / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D002712:Chlorides; D010758:Phosphorus; D008536:Meglumine; D012964:Sodium; D011188:Potassium