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Ca 2+ ‐sensing receptor‐mediated regulation of volume‐sensitive Cl − channels in human epithelial cells
Author(s) -
Shimizu Takahiro,
Morishima Shigeru,
Okada Yasunobu
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00457.x
Subject(s) - extracellular , gtpgammas , depolarization , forskolin , biophysics , chemistry , intracellular , stimulation , receptor , biochemistry , g protein , endocrinology , biology
1 Since extracellular Ca 2+ or Mg 2+ has been reported to modulate swelling‐activated Cl − currents, we examined the expression of the G protein‐coupled Ca 2+ ‐sensing receptor (CaR) and its involvement in the regulation of volume‐sensitive Cl − channels in a human epithelial cell line (Intestine 407). 2 Reverse transcriptase‐polymerase chain reaction and immunoblotting analysis showed that Intestine 407 cells express CaR mRNA and protein. 3 The swelling‐activated whole‐cell Cl − current was voltage‐independently augmented by extracellular Ca 2+ or Mg 2+ . In addition, Ca 2+ or Mg 2+ voltage‐dependently accelerated the inactivation kinetics of the Cl − current. 4 Neomycin, spermine and La 3+ augmented volume‐sensitive Cl − currents. However, these CaR agonists failed to affect depolarization‐induced inactivation. 5 Intracellular application of GTPγS, but not GDPβS, increased the amplitude of the swelling‐induced Cl − current without affecting the basal current. The upregulating effect of Ca 2+ on the Cl − current amplitude was abolished by either GTPγS or GDPβS. In contrast, GTPγS and GDPβS failed to affect the inactivation kinetics of the Cl − current and the accelerating effect of Ca 2+ thereon. 6 The Cl − current amplitude was enlarged by stimulation with forskolin, dibutyryl cAMP and IBMX. During the cAMP stimulation, extracellular Ca 2+ failed to increase the Cl − current but did accelerate depolarization‐induced inactivation. 7 It is concluded that stimulation of the CaR induces upregulation of volume‐sensitive Cl − channels via a G protein‐mediated increase in intracellular cAMP in the human epithelial cell. However, the accelerating effect of extracellular divalent cations on the inactivation kinetics of the Cl − current is induced by a mechanism independent of the CaR and cAMP.