Open AccessDepletion of intracellular calcium stores facilitates the influx of extracellular calcium in platelet derived growth factor stimulated A172 glioblastoma cells
Author(s) -
Vereb György,
Szöllosi János,
Mátyus László,
Balázs Margit,
Hyun William C.,
Feuerstein Burt G.
Publication year - 1996
Publication title -
cytometry
Language(s) - English
Resource type - Journals
eISSN - 1097-0320
pISSN - 0196-4763
DOI - 10.1002/(sici)1097-0320(19960501)24:1<64::aid-cyto8>3.0.co;2-i
Subject(s) - extracellular , calcium , intracellular , calcium in biology , bapta , chemistry , thapsigargin , biophysics , voltage dependent calcium channel , calcium channel , fura 2 , plasma membrane ca2+ atpase , platelet derived growth factor receptor , biochemistry , cytosol , biology , growth factor , atpase , receptor , enzyme , organic chemistry
Abstract Calcium signaling in non‐excitable cells is the consequence of calcium release from intracellular stores, at times followed by entry of extracellular calcium through the plasma membrane. To study whether entry of calcium depends upon the level of saturation of intracellular stores, we measured calcium channel opening in the plasma membrane of single confluent A172 glioblastoma cells stimulated with platelet derived growth factor (PDGF) and/or bradykinin (BK). We monitored the entry of extracellular calcium by measuring manganese quenching of Indo‐1 fluorescence. PDGF raised intracellular calcium concentration ([Ca 2+ ] i ) after a dose‐dependent delay (t del ) and then opened calcium channels after a dose‐independent delay (t ch ). At higher doses (>3 nM), BK increased [Ca 2+ ] i , after a t del ∼0 s, and t ch decreased inversely with both dose and peak [Ca 2+ ] i . Experiments with thapsigargin (TG), BK, and PDGF indicated that BK and PDGF share intracellular Ca 2+ pools that are sensitive to TG. When these stores were depleted by treatment with BK and intracellular BAPTA, tdel did not change, but t ch fell to almost 0 s in PDGF stimulated cells, indicating that depletion of calcium stores affects calcium channel opening in the plasma membrane. Our data support the capacitative model for calcium channel opening and the steady‐state model describing quantal Ca 2+ release from intracellular stores. © 1996 Wiley‐Liss, Inc.