Mobilization of calcium by inositol trisphosphates from permeabilized rat parotid acinar cells. Evidence for translocation of calcium from uptake to release sites within the inositol 1,4,5-trisphosphate- and thapsigargin-sensitive calcium pool

F S Menniti, G S Bird, H Takemura, Ole Thastrup, B V Potter, J W Putney

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Abstract

D-myo-Inositol (1,4,5)-trisphosphate ((1,4,5)IP3)-induced Ca2+ release and subsequent Ca2+ reuptake were investigated in saponin-permeabilized rat parotid acinar cells. Following the rapid release of Ca2+ by (1,4,5)IP3, Ca2+ was resequestered. The sequential addition of submaximal concentrations of (1,4,5)IP3 resulted in sequential Ca2+ release. However, when the cells were challenged with the poorly metabolized (1,4,5)IP3 analogues, (1,4,5)IPS3 or (2,4,5)IP3, or under conditions where the metabolism of authentic (1,4,5)IP3 was reduced, Ca2+ reuptake again occurred, but sequestered Ca2+ was not released by subsequent additions of (1,4,5)IP3. The sequestered Ca2+ was, however, released by thapsigargin, an agent which inhibits active Ca2+ uptake into the (1,4,5)IP3-sensitive pool. Furthermore, the rate of thapsigargin-induced release was significantly increased in the continued presence of an (1,4,5)IP3 stimulus. Thus, Ca2+ reuptake apparently occurred into the (1,4,5)IP3- and thapsigargin-sensitive Ca2+ store and (1,4,5)IP3 continued to influence the permeability of this pool to Ca2+ during Ca2+ reuptake. In contrast to the findings in permeabilized cells, Ca2+ reuptake did not occur in the sustained presence of (1,4,5)IP3 in intact parotid cells. We conclude that cell permeabilization reveals a kinetic, and presumably structural, separation of Ca2+ uptake and release sites within the (1,4,5)IP3-regulated intracellular organelle.
Original languageEnglish
JournalJournal of Biological Chemistry
Volume266
Issue number21
Pages (from-to)13646-53
Number of pages8
ISSN0021-9258
Publication statusPublished - 1991
Externally publishedYes

Keywords

  • Animals
  • Calcium
  • Cell Compartmentation
  • Cell Membrane Permeability
  • Cells, Cultured
  • Diphosphoglyceric Acids
  • Egtazic Acid
  • Heparin
  • Inositol 1,4,5-Trisphosphate
  • Kinetics
  • Organelles
  • Parotid Gland
  • Rats
  • Terpenes
  • Thapsigargin
  • Time Factors

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