Ca 2+ responses of pulmonary arterial myocytes to acute hypoxia require release from ryanodine and inositol trisphosphate receptors in sarcoplasmic reticulum

Jian Wang, Larissa A. Shimoda, J. T. Sylvester

Research output: Contribution to journalArticlepeer-review

Abstract

In pulmonary arterial smooth muscle cells (PASMC), acute hypoxia increases intracellular Ca 2+ concentration ([Ca 2+]i) by inducing Ca 2+ release from the sarcoplasmic reticulum (SR) and Ca 2+ influx through store-and voltage-operated Ca 2+ channels in sarcolemma. To evaluate the mechanisms of hypoxic Ca 2+ release, we measured [Ca 2+]i with fluorescent microscopy in primary cultures of rat distal PASMC. In cells perfused with Ca 2+-free Krebs Ringer bicarbonate solution (KRBS), brief exposures to caffeine (30 mM) and norepinephrine (300 μM), which activate SR ryanodine and inositol trisphosphate receptors (RyR, IP3R), respectively, or 4% O 2 caused rapid transient increases in [Ca 2+]i, indicating intracellular Ca 2+ release. Preexposure of these cells to caffeine, norepinephrine, or the SR Ca 2+-ATPase inhibitor cyclopiazonic acid (CPA; 10 μM) blocked subsequent Ca 2+ release to caffeine, norepinephrine, and hypoxia. The RyR antagonist ryanodine (10 μM) blocked Ca 2+ release to caffeine and hypoxia but not norepinephrine. The IP3R antagonist xestospongin C (XeC, 0.1 μM) blocked Ca 2+ release to norepinephrine and hypoxia but not caffeine. In PASMC perfused with normal KRBS, acute hypoxia caused a sustained increase in [Ca 2+]i that was abolished by ryanodine or XeC. These results suggest that in rat distal PASMC 1) the initial increase in [Ca 2+]i induced by hypoxia, as well as the subsequent Ca 2+ influx that sustained this increase, required release of Ca 2+ from both RyR and IP 3R, and 2) the SR Ca 2+ stores accessed by RyR, IP 3R, and hypoxia functioned as a common store, which was replenished by a CPA-inhibitable Ca 2+-ATPase.

Original languageEnglish (US)
Pages (from-to)L161-L168
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume303
Issue number2
DOIs
StatePublished - Jul 15 2012

Keywords

  • Caffeine
  • Cyclopiazonic acid
  • Intracellular calcium concentration
  • Norepinephrine
  • Store-operated calcium entry

ASJC Scopus subject areas

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

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