Relationship between Ca2+ sparklets and sarcoplasmic reticulum Ca2+ load and release in rat cerebral arterial smooth muscle

Am J Physiol Heart Circ Physiol. 2011 Dec;301(6):H2285-94. doi: 10.1152/ajpheart.00488.2011. Epub 2011 Oct 7.

Abstract

Ca(+) sparklets are subcellular Ca(2+) signals produced by the opening of sarcolemmal L-type Ca(2+) channels. Ca(2+) sparklet activity varies within the sarcolemma of arterial myocytes. In this study, we examined the relationship between Ca(2+) sparklet activity and sarcoplasmic reticulum (SR) Ca(2+) accumulation and release in cerebral arterial myocytes. Our data indicate that the SR is a vast organelle with multiple regions near the sarcolemma of these cells. Ca(2+) sparklet sites were located at or <0.2 μm from SR-sarcolemmal junctions. We found that while Ca(2+) sparklets increase the rate of SR Ca(2+) refilling in arterial myocytes, their activity did not induce regional variations in SR Ca(2+) content or Ca(2+) spark activity. In arterial myocytes, L-type Ca(2+) channel activity was independent of SR Ca(2+) load. This ruled out a potential feedback mechanism whereby SR Ca(2+) load regulates the activity of these channels. Together, our data suggest a model in which Ca(2+) sparklets contribute Ca(2+) influx into a cytosolic Ca(2+) pool from which sarco(endo)plasmic reticulum Ca(2+)-ATPase pumps Ca(2+) into the SR, indirectly regulating SR function.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Channels, L-Type / metabolism
  • Calcium Signaling*
  • Cerebral Arteries / metabolism
  • Luminescent Proteins / biosynthesis
  • Luminescent Proteins / genetics
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / metabolism*
  • Myocytes, Smooth Muscle / metabolism*
  • Protein Sorting Signals
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Fusion Proteins / biosynthesis
  • Red Fluorescent Protein
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Sarcolemma / metabolism*
  • Sarcoplasmic Reticulum / metabolism*
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism
  • Time Factors
  • Transfection

Substances

  • Calcium Channels, L-Type
  • Luminescent Proteins
  • Protein Sorting Signals
  • Recombinant Fusion Proteins
  • Ryanodine Receptor Calcium Release Channel
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium