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Extracellular ATP raises cytosolic calcium and activates basolateral chloride conductance in Necturus proximal tubule
Author(s) -
Bouyer Patrice,
Paulais Marc,
Coug Marc,
Hulin Philippe,
Anagnostopoulos Takis,
Planelles Gabrielle
Publication year - 1998
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.1469-7793.1998.535bk.x
Subject(s) - necturus , thapsigargin , extracellular , chemistry , biophysics , depolarization , intracellular , adenosine , epithelial polarity , adenosine triphosphate , membrane potential , ionomycin , medicine , biochemistry , endocrinology , biology , membrane
1 Extracellular nucleotides modulate ionic transport mechanisms in various epithelia. In the present study, we investigated the effects of extracellular ATP on the intracellular free Ca 2+ concentration ([Ca 2+ ] i ) and electrophysiological properties of Necturus maculosus proximal convoluted tubule (PCT). 2 ATP raised [Ca 2+ ] i in microdissected fura‐2‐loaded PCTs (half‐maximal effect, ≈15 μmol l −1 ATP). The initial ATP‐induced changes in [Ca 2+ ] i were not blunted by the removal of external Ca 2+ nor by the presence of Ca 2+ channel blockers, but were abolished by thapsigargin and suramin. The sequence for the potency of various agonists on [Ca 2+ ] i was 2‐methylthioATP (2MeSATP) = ADP = ATP ≫ UTP, 2′,3′‐ O‐( 4‐benzoilbenzoil) ATP (BzATP), α,β‐methylene ATP (AMPCPP), adenosine. 3 In vivo electrophysiological measurements showed that 100 μmol l −1 peritubular ATP added to a Ringer solution reduced the basolateral cell membrane potential ( V m ) and increased the cell membrane input conductance. In a low Cl − solution, this ATP‐induced depolarization was enhanced. These effects were inhibited by 1 mmol l −1 SITS, consistent with the activation of a basolateral Cl − conductance. 4 The ATP‐induced change in V m was reproduced by ADP but not by UTP or adenosine, and was prevented by suramin. 5 The ATP‐induced membrane depolarization was not influenced by thapsigargin, BAPTA AM, or staurosporin and was not reproduced by manoeuvres increasing [Ca 2+ ] i or intracellular cAMP content. 6 We conclude that, in Necturus PCT, a P2y receptor mobilizes Ca 2+ mainly from intracellular pools and increases a basolateral Cl − conductance, G Cl . The activation of G Cl occurs by a mechanism which is not related either to an increase in [Ca 2+ ] i or cAMP content, or to PKC activation.