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P 2U nucleotide receptor activation in rat glial cell line induces [Ca 2+ ] i oscillations which depend on cytosolic pH
Author(s) -
Czubayko Uwe,
Reiser Georg
Publication year - 1996
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/(sici)1098-1136(199602)16:2<108::aid-glia3>3.0.co;2-#
Subject(s) - biophysics , extracellular , cytosol , agonist , bradykinin , receptor , biology , purinergic receptor , intracellular , calcium , endocrinology , medicine , biochemistry , enzyme
In single rat glioma cells, the signal transduction process activated by the UTP sensitive purinergic nucleotide receptor was studied by determining [Ca 2+ ] i by Fura‐2 fluorescence and measuring pH by BCECF fluorescence to elucidate the control of [Ca 2+ ] i oscillations by intracellular pH. Addition of UTP for long time periods (some min) causes a [Ca 2+ ] i response composed of i) an initial large peak and a following sustained increase (160 s duration), and ii) subsequent regular [Ca 2+ ] i oscillations (amplitude 107 nM, frequency 1.5 oscillations per min). The maintenance of the [Ca 2+ ] i oscillations depends on the continued presence of agonist. The oscillations are abolished by reducing extracellular Ca 2+ concentration. The interaction of UTP receptors and bradykinin receptors during the [Ca 2+ ] i oscillations was investigated because previous studies have already shown that the peptide causes comparable [Ca 2+ ] i oscillations. During [Ca 2+ ] i oscillations induced by UTP or bradykinin, long‐term admission of both hormones (400–500 s) causes a large initial response superimposed on regular [Ca 2+ ] i oscillations. Short pulses (12 s) of the second agonist given in any phase of the oscillations induce large [Ca 2+ ] i peaks. In both cases, the following oscillations are not disturbed. The influence of cytosolic pH was studied by alkalinizing pH i by application of NH 4 Cl. [Ca 2+ ] i oscillations stop after addition of NH 4 Cl. Recovery of NH 4 Cl‐induced alkalinization is reduced by furosemide. To the same degree, the interruption of [Ca 2+ ] i oscillations is significantly prolonged in the presence of furosemide. Thus cytosolic alkalinization suppresses hormone‐induced [Ca 2+ ] i oscillations in rat glioma cells. The understanding of the molecular mechanism of this interference of pH should provide an important contribution for unravelling the function of cytosolic pH in cellular signal transduction. © 1996 Wiley‐Liss, Inc.