Inositol 1,4,5-trisphosphate-induced Ca2+ release is regulated by cytosolic Ca2+ in intact skeletal muscle

José R. López, Andre Terzic

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Microinjection of inositol 1,4,5-trisphosphate (InsP3) into intact skeletal muscle fibers isolated from frogs (Rana temporaria) increased resting cytosolic Ca2+ concentration ([Ca2+](i)) as measured by double-barreled Ca2+-selective microelectrodes. In contrast, microinjection of inositol 1-phosphate, inositol 1,4-biphosphate, and inositol 1,4,5,6-tetrakisphosphate did not induce changes in [Ca2+](i). Incubation in low-Ca2+ solution, or in the presence of L-type Ca2+ channel blockers did not affect InsP3-induced release of cytosolic Ca2+. Neither ruthenium red, a blocker of ryanodine receptor Ca2+ release channels, nor cytosolic Mg2+, a known inhibitor of the Ca2+-induced Ca2+-release process, modified the InsP3-induced release of cytosolic Ca2+. However, heparin, a blocker of InsP3 receptors, inhibited InsP3-induced release of cytosolic Ca2+. Also, pretreatment with dantrolene or azumulene, two inhibitors of cytosolic Ca2+ release, reduced [Ca2+](i), and prevented InsP3 from inducing release of cytosolic Ca2+. Incubation in caffeine or lengthening of the muscle increased [Ca2+](i) and enhanced the ability of InsP3 to induce release of cytosolic Ca2+. These results indicate that InsP3, at physiological concentrations, induces Ca2+ release in intact muscle fibers, and suggest that the InsP3-induced Ca2+ release is regulated by [Ca2+](i). A Ca2+-dependent effect of InsP3 on cytosolic Ca2+ release could be of importance under physiological or pathophysiological conditions associated with alterations in cytosolic Ca2+ homeostasis.

Original languageEnglish (US)
Pages (from-to)782-790
Number of pages9
JournalPflugers Archiv European Journal of Physiology
Volume432
Issue number5
DOIs
StatePublished - Sep 5 1996

Keywords

  • Calcium
  • Dantrolene
  • Heparin
  • Inositol trisphosphate
  • Ion-selective microelectrodes
  • Ruthenium red
  • Skeletal muscle

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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