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The effects of extracellular and intracellular pH on intracellular Ca 2+ regulation in guinea‐pig detrusor smooth muscle
Author(s) -
Wu C.,
Fry C. H.
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.1469-7793.1998.131br.x
Subject(s) - extracellular , intracellular , acidosis , intracellular ph , alkalosis , chemistry , biophysics , carbachol , calcium , caffeine , biochemistry , endocrinology , medicine , biology , receptor , organic chemistry
1 Intracellular pH (pH i ) and intracellular [Ca 2+ ] ([Ca 2+ ] i ) were measured during changes to superfusate P CO2 and/or [NaHCO 3 ]. Changes to superfusate P CO2 produced sustained changes to pH i and [Ca 2+ ] i , while changes to [NaHCO 3 ] altered only extracellular pH (pH o ). 2 Carbachol or caffeine induced a transient rise of [Ca 2+ ] i due to Ca 2+ release from an intracellular store. This Ca 2+ transient was reduced by extracellular acidosis, but increased by intracellular acidosis. Alkalosis in either compartment produced opposite effects to acidosis. Changes to the Ca 2+ transient mirrored those to phasic tension previously reported in this preparation. 3 A raised superfusate [K + ] also induced a Ca 2+ transient, due to transmembrane influx of Ca 2+ . This transient was depressed by extracellular acidosis, but unaffected by changes to pH i . The L‐type Ca 2+ current was similarly affected by changes to pH o , but not by alteration of pH i . 4 The results suggest that extracellular acidosis depresses the Ca 2+ transient by reducing transmembrane influx through the L‐type Ca 2+ channel. The increase in the carbachol‐ and caffeine‐induced Ca 2+ transients by intracellular acidosis is due to enhancement of Ca 2+ uptake into intracellular stores as a result of a raised resting [Ca 2+ ] i .