Intracellular acidification associated with changes in free cytosolic calcium: Evidence for Ca2+/H+ exchange via a plasma membrane Ca2+-ATPaSe in vascular smooth muscle Cells

John T. Daugirdas, Javier Arrieta, Minghao Ye, Guillermo Flores, Daniel Batlle*

*Corresponding author for this work

Research output: Contribution to journalArticle

46 Scopus citations

Abstract

The purpose of this study was to define the mechanism whereby agonists that increase free cytosolic calcium (Cai2+) affect intracellular pH (pHi) in smooth muscle. Rat aortic vascular smooth muscle cells grown on coverslips were loaded with BCECF/AM or fura-2/AM for continuous monitoring of pHi or Cai2+, respectively, in a HCO-3/CO2-containing medium. Recovery from rapid increases in Cai2+ produced by 1 μM angiotensin (Ang) II (Δ Cai2+ -229±43 nM) or 1 μM ionomycin (Δ Cai2+ -148±19 nM) was accompanied by a fall in pHi (Δ pHi, -0.064±0.0085 P < 0.01, and -0.05±0.012 pH units, P < 0.01, respectively). Neither the fall in pHi nor the rise in Cai2+ elicited by Ang II was prevented by pretreatment with agents which block the action of this agonist on pHi via the stimulation of the Cl/ HC03 exchangers (DIDS, 50 μM) or the Na+/H+ antiporter (EIPA, 50 μM). In the presence of DIDS and EIPA, Ang II produced a fall in pHi (Δ pHi, -0.050±0.014, P < 0.01) and a rise in Cai2+ (Δ Ca2+ 252±157 nM, P < 0.01). That the change in pHi was secondary to changes in Cai2+ was inferred from the finding that, when the rise in Cai2+ elicited by Ang II was prevented by preincubation with a Ca2+ buffer, BAPTA (60 μM), the fall in pHi was abolished as well (Δ pHi, 0.0014±0.0046). The pHi fall produced by Ang II and ionomycin was prevented by cadmium at a very low concentration (20 nM) which is known to inhibit plasma membrane Ca2+-ATPase activity (Δ pHi -0.002±0.0006 and -0.0016 pH units, respectively). Cadmium also blunted Cai2+ recovery after Ang II and ionomycin. These findings suggest that the fall in pHi produced by these agents is due to H+ entry coupled to Ca2+ extrusion via the plasma membrane Ca2+-ATPase. Our results indicate that agonists that increase Cai2+ cause intracellular acidification as a result of Ca2+/H+ exchange across the plasma membrane. This process appears to be mediated by a plasma membrane Ca2+-ATPase which, in the process of extruding Ca2+ from the cell, brings in [H+] and thus acidifies the cell.

Original languageEnglish (US)
Pages (from-to)1480-1489
Number of pages10
JournalJournal of Clinical Investigation
Volume95
Issue number4
DOIs
StatePublished - Jan 1 1995

Keywords

  • Angiotensin II
  • Ca-transporting-ATPase
  • Ca/H exchanger
  • Cl/HCO exchanger
  • Intracellular pH
  • Muscle
  • Smooth
  • Vascular

ASJC Scopus subject areas

  • Medicine(all)

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