Organization of Ca2+ Stores in Vascular Smooth Muscle: Functional Implications

  1. Derek J. Chadwick Organizer and
  2. Jamie A. Goode
  1. Mordecai P. Blaustein1,
  2. Vera A. Golovina1,
  3. Hong Song1,
  4. Jacqueline Choate1,
  5. Lubomira Lencesova1,
  6. Shawn W. Robinson2 and
  7. W. Gil Wier1

Published Online: 7 OCT 2008

DOI: 10.1002/0470853050.ch10

Role Of The Sarcoplasmic Reticulum In Smooth Muscle: Novartis Foundation Symposium 246

Role Of The Sarcoplasmic Reticulum In Smooth Muscle: Novartis Foundation Symposium 246

How to Cite

Blaustein, M. P., Golovina, V. A., Song, H., Choate, J., Lencesova, L., Robinson, S. W. and Wier, W. G. (2008) Organization of Ca2+ Stores in Vascular Smooth Muscle: Functional Implications, in Role Of The Sarcoplasmic Reticulum In Smooth Muscle: Novartis Foundation Symposium 246 (eds D. J. Chadwick and J. A. Goode), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/0470853050.ch10

Author Information

  1. 1

    Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA

  2. 2

    Department of Medicine (Cardiology Division), University of Maryland School of Medicine, Baltimore, MD 21201, USA

Publication History

  1. Published Online: 7 OCT 2008
  2. Published Print: 15 JUN 2002

Book Series:

  1. Novartis Foundation Symposia

Book Series Editors:

  1. Novartis Foundation

ISBN Information

Print ISBN: 9780470844793

Online ISBN: 9780470853054

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Summary

Much evidence suggests that caffeine/ryanodine (Caf/Ry)-releasable and inositol-1,4,5-trisphosphate (InsP3)-releasable Ca2+ stores in the sarcoplasmic reticulum (SR) of smooth muscles are at least partially distinct. We directly visualized SR stores in primary-cultured rat mesenteric artery myocytes with high-resolution digital imaging and the low-affinity Ca2+ indicator, Furaptra Kd=75.6µM. The SR appears to be a continuous tubular network. Nevertheless, SR Ca2+ stores are organized into small, separate, functionally independent compartments. Cyclopiazonic acid (CPA; inhibits SR Ca2+ pump) and Caf (or Ry) release Ca2+ from different, spatially distinct compartments. Similar heterogeneity is seen with serotonin (acts via InsP3), which unloads only the CPA-sensitive compartments. Some of the SR (‘junctional’ SR; jSR) lies within 12–15 nm of the plasmalemma (PL). The jSR, the overlying PL microdomains, and the intervening, tiny volume of cytosol form junctional complexes (‘PLasmERosomes’). Na+ pumps with high-ouabain-affinity α2 or α3 subunits, Na+/Ca2+ exchangers, and store-operated channels are confined to these PL microdomains, whereas Na+ pumps with low-ouabain-affinity α1 subunits and plasma membrane Ca2+ pumps are uniformly distributed. As a result of this organization, low-dose ouabain can selectively modulate Na+ and Ca2+ concentrations in the PLasmERosomes and jSR Ca2+ stores, and can thereby regulate Ca2+ signalling.