Stored calcium modulates inositol phosphate synthesis in cultured smooth muscle cells

D. M. Berman, W. F. Goldman

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Cytosolic Ca2+ concentrations ([Ca2+](cyt)) and [3H]inositol phosphates ([3H]InsP) were correlated while varying the Ca2+ content of the sarcoplasmic reticulum (SR) in cultured A7r5 cells at rest and during activation with [Arg8]-vasopressin (AVP). Thapsigargin (TG) raised and superfusion with 0 Ca2+ lowered [Ca2+](cyt), but both treatments decreased SR Ca2+ and AVP-evoked Ca2+ transients. Neither TG nor 0 Ca2+ affected basal [3H]InsP, but both treatments increased AVP-evoked synthesis of [3H]InsP. Exposure for several minutes to 40 mM K+ solution, BAY K 8644, or low-Na+ solution all elevated [Ca2+](cyt) and, thereby, increased SR Ca2+, as manifested by augmented AVP-evoked Ca2+ transients. In all three cases, AVP-evoked, but not basal, [3H]InsP were reduced. The inhibitory effect of 40 mM K+ on AVP-evoked [3H]InsP synthesis was blocked when SR Ca2+ uptake was prevented by TG. Brief (30-s) exposures to 40 mM K+, which elevated [Ca2+](cyt) but not SR Ca2+ loading, did not modify AVP-evoked [3H]InsP synthesis or Ca2+ transients. These results demonstrate an inverse relationship between SR Ca2+ content and evoked [3H]-InsP synthesis. Moreover, they suggest that SR Ca2+ may serve as a signal that modulates sarcolemmal [3H]InsP formation.

Original languageEnglish (US)
Pages (from-to)C535-C539
JournalAmerican Journal of Physiology - Cell Physiology
Issue number2 32-2
StatePublished - Jan 1 1992
Externally publishedYes


  • A7r5 cells
  • calcium release
  • fura-2
  • sarcoplasmic reticulum
  • thapsigargin
  • vasopressin

ASJC Scopus subject areas

  • Cell Biology
  • Clinical Biochemistry
  • Physiology


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