Intracellular pH regulates voltage-dependent Ca2+ channels in porcine tracheal smooth muscle cells

M. Yamakage, K. S. Lindeman, C. A. Hirshman, T. L. Croxton

Research output: Contribution to journalArticle

Abstract

Changes in CO2 or in pH modify airway smooth muscle contractility. To investigate the mechanisms involved, we compared K+-induced contractions in porcine bronchial rings exposed to different CO2 concentrations and directly measured the effects of changes in intracellular (pH(i)) or extracellular pH (pH(o)) on Ca2+ currents (I(Ca)) through voltage-dependent Ca2+ channels (VDC) in porcine tracheal smooth muscle cells. Hypocapnia and hypercapnia caused leftward and rightward shifts, respectively, in the dose-response to K+ (P < 0.05) but did not change the maximum force obtained. Peak I(Ca) (10 mM external Ca2+) elicited by depolarizing pulses from 80 mV was maximal [- 265 ± 12 pA (mean ± SE), n = 19] at + 10 mV. Intracellular acidification decreased the peak I(Ca) at + 10 mV from 261 ± 20 pA to -177 ± 12 pA (P < 0.05, n = 4), while intracellular alkalinization increased the peak I(Ca) at + 10 mV from -302 ± 27 pA to - 368 ± 26 pA (P < 0.05, n = 4). Changes in pH(o) had little effect on I(Ca). There was no shift in the voltage- dependence of induced I(Ca) with any change. We conclude that pH(i), but not pH(o), directly modulates the entry of Ca2+ into airway smooth muscle cells through VDC. This mechanism may contribute to regulation of airway tone by CO2.

Original languageEnglish (US)
Pages (from-to)L642-L646
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume268
Issue number4 12-4
DOIs
StatePublished - 1995

Keywords

  • airway smooth muscle
  • hypercapnia
  • hypocapnia
  • pig
  • whole cell patch clamp

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology

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