Functionally Separate Intracellular Ca2+ Stores in Smooth Muscle

  • Flynn E
  • Bradley K
  • Muir T
 et al. 
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In smooth muscle, release via the inositol 1,4,5-trisphosphate (Ins(1,4,5)P 3 R) and ryanodine receptors (RyR) on the sarcoplasmic reticulum (SR) controls oscil-latory and steady-state cytosolic Ca 2؉ concentrations ([Ca 2؉ ] c). The interplay between the two receptors, itself determined by their organization on the SR, establishes the time course and spatial arrangement of the Ca 2؉ signal. Whether or not the receptors are co-localized or distanced from each other on the same store or whether they exist on separate stores will significantly affect the Ca 2؉ signal produced by the SR. To date these matters remain unresolved. The functional arrangement of the RyR and Ins(1,4,5)P 3 R on the SR has now been examined in isolated single voltage-clamped colonic myocytes. De-pletion of the ryanodine-sensitive store, by repeated ap-plication of caffeine, in the presence of ryanodine, abol-ished the response to Ins(1,4,5)P 3 , suggesting that Ins(1,4,5)P 3 R and RyR share a common Ca 2؉ store. Ca 2؉

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  • Elaine R M Flynn

  • Karen N. Bradley

  • Thomas C. Muir

  • John G. McCarron

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