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Independent changes of intracellular calcium and pH in identified leech glial cells
Author(s) -
Deitmer Joachim W.,
Schneider HansPeter,
Munsch Thomas
Publication year - 1993
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.440070405
Subject(s) - depolarization , biophysics , membrane potential , intracellular , intracellular ph , hirudo medicinalis , leech , biology , cotransporter , reversal potential , ammonium , calcium , fura 2 , neuroglia , electrophysiology , biochemistry , chemistry , neuroscience , central nervous system , patch clamp , sodium , cytosol , enzyme , organic chemistry , world wide web , computer science
The intracellular Ca 2+ (Ca 2+ i ) and the intracellular pH (pH i ) were measured in identified neuropile glial cells in the central nervous system of the leech Hirudo medicinalis , using the fluorescent dye fura‐2, and double‐barrelled, neutral carrier, pH‐sensitive microelectrodes. Different stimuli were used to elicit Ca 2+ i and/or pH i changes, such as application of ammonium, high external K + ‐concentration, and low external pH. Ammonium (20 mM) and high external K + (20 mM), which depolarized the glial membrane by 20–30 mV, evoked rapid and large rises of Ca 2+ i . In contrast to the Ca 2 i changes, amplitude and direction of the pH i changes were dependent on the presence of CO 2 /HCO 3 − in the saline. The addition of CO 2 /HCO 3 − , and the subsequent reduction of external pH from 7.4 to 7.0, had no effect on Ca 2+ i , but caused significant changes of pH i . The results suggest that the ammonium‐ and K + ‐induced Ca 2+ i rises were due to the membrane depolarization leading to a Ca 2+ influx through voltage‐gated Ca 2+ channels in the glial membrane, while the pH i changes resulted from movements of ammonia and from the activation or inhibition of the Na + ‐HCO 3 − cotransporter. This indicates that changes of intracellular Ca 2+ and pH can occur independently of each other, suggesting that the homeostasis of these ions is not necessarily interrelated in these glial cells.