Modulation of calcium homeostasis in cultured rat aortic endothelial cells by intracellular acidification

R. C. Ziegelstein, L. Cheng, P. S. Blank, H. A. Spurgeon, E. G. Lakatta, R. G. Hansford, M. C. Capogrossi

Research output: Contribution to journalArticlepeer-review

Abstract

Acidosis produces vasodilation in a process that may involve the vascular endothelium. Because synthesis and release of endothelium-derived vasodilatory substances are linked to an increase in cytosolic calcium concentration ([Ca2+](i)), we examined the effect of intracellular acidification on cultured rat aortic endothelial cells loaded either with the pH-sensitive probe carboxy-seminaphthorhodafluor-1 or the Ca2+-sensitive fluorescent probe indo 1. The basal cytosolic pH (pH(i)) of endothelial monolayers in a 5% CO2-HCO3/- buffer was 7.27 ± 0.02 and that in a bicarbonate-free solution was 7.22 ± 0.03. Acidification was induced either by removal of NH4Cl (ΔpH(i) = -0.10 ± 0.02), changing from a bicarbonate- free to a 5% CO2-HCO3/--buffered solution at constant buffer pH (ΔpH(i) = -0.18 ± 0.03), or changing from a 5% to a 20% CO2-HCO3/- solution (ΔpH(i) = -0.27 ± 0.07). Regardless of the method used, intracellular acidification increased [Ca2+](i) as indexed by indo 1 fluorescence. The increase in [Ca2+](i) induced by changing from a 5 to a 20% CO2-HCO3/- solution was not significantly altered by removal of buffer Ca2+ either before or after depletion of bradykinin- and thapsigargin-sensitive intracellular Ca2+ stores. Thus intracellular acidification of vascular endothelial cells releases Ca2+ into the cytosol either from pH-sensitive intracellular buffer sites, mitochondria, or from bradykinin- and thapsigargin-insensitive intracellular stores. This Ca2+ mobilization may be linked to endothelial synthesis and release of vasodilatory substances during acidosis.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume265
Issue number4 34-4
Publication statusPublished - 1993

Keywords

  • acid-base equilibrium
  • acidosis
  • carboxy- seminaphthorhodafluor-1
  • cytosolic pH
  • indo 1

ASJC Scopus subject areas

  • Physiology
  • Agricultural and Biological Sciences(all)

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