title: Three-dimensional distribution of ryanodine receptor clusters in cardiac myocytes.
abstract: The clustering of ryanodine receptors (RyR2) into functional Ca2+ release units is central to current models for cardiac excitation-contraction (E-C) coupling. Using immunolabeling and confocal microscopy, we have analyzed the distribution of RyR2 clusters in rat and ventricular atrial myocytes. The resolution of the three-dimensional structure was improved by a novel transverse sectioning method as well as digital deconvolution. In contrast to earlier reports, the mean RyR2 cluster transverse spacing was measured 1.05 microm in ventricular myocytes and estimated 0.97 microm in atrial myocytes. Intercalated RyR2 clusters were found interspersed between the Z-disks on the cell periphery but absent in the interior, forming double rows flanking the local Z-disks on the surface. The longitudinal spacing between the adjacent rows of RyR2 clusters on the Z-disks was measured to have a mean value of 1.87 microm in ventricular and 1.69 microm in atrial myocytes. The measured RyR2 cluster distribution is compatible with models of Ca2+ wave generation. The size of the typical RyR2 cluster was close to 250 nm, and this suggests that approximately 100 RyR2s might be present in a cluster. The importance of cluster size and three-dimensional spacing for current E-C coupling models is discussed.
authors.affiliation: University of Kentucky, College of Medicine, Lexington, Kentucky 40536-0509, USA. YeChen-Izu@uky.edu
authors.forename: Ye
authors.initials: Y
authors.lastname: Chen-Izu
authors.forename: Stacey L
authors.initials: SL
authors.lastname: McCulle
authors.forename: Chris W
authors.initials: CW
authors.lastname: Ward
authors.forename: Christian
authors.initials: C
authors.lastname: Soeller
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Allen
authors.forename: Cal
authors.initials: C
authors.lastname: Rabang
authors.forename: Mark B
authors.initials: MB
authors.lastname: Cannell
authors.forename: C William
authors.initials: CW
authors.lastname: Balke
authors.forename: Leighton T
authors.initials: LT
authors.lastname: Izu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D003198:Computer Simulation; D006325:Heart Atria / Q000166:cytology / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D008955:Models, Cardiovascular; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium