Localization of Ryanodine Receptors in Smooth Muscle

Abstract

Abstract-The ryanodine receptor (RyR) in aortic and vas deferens smooth muscle was localized using immunofluorescence confocal microscopy and immunoelectron microscopy. Indirect immunofluorescent labeling of aortic smooth muscle with anti-RyR antibodies showed a patchy network-like staining pattern throughout the cell cytoplasm, excluding nuclei, in aortic smooth muscle and localized predominantly to the cell periphery in the vas deferens. This distribution is consistent with that of the sarcoplasmic reticulum (SR) network, as demonstrated by electron micrographs of osmium ferrocyanidestained SR in the two smooth muscles. Immunoelectron microscopy of vas deferens smooth muscle showed anti-RyR antibodies localized to both the sparse central and predominant peripheral SR elements. We conclude that RyR-Ca 2ϩ -release channels are present in both the peripheral and central SR in aortic and vas deferens smooth muscle. This distribution is consistent with the possibility that both regions are release sites, as indicated by results of electron probe analysis, which show a decrease in the Ca 2ϩ content of both peripheral and internal SR in stimulated smooth muscles. The complex distribution of inositol 1,4,5-trisphosphate and ryanodine receptors (present study) is compatible with their proposed roles as agonist-induced Ca 2ϩ -release channels and origins of Ca 2ϩ sparks, Ca 2ϩ oscillations, and Ca 2ϩ waves. (Circ Res. 1998;82:175-185.) Key Words: smooth muscle Ⅲ ryanodine receptor Ⅲ electron microscopy Ⅲ confocal microscopy immunofluorescence

Phosphatidylinositol 3,5-bisphosphate increases intracellular free Ca2+in arterial smooth muscle cells and elicits vasocontraction

“…The aortic contractions caused by PI(3,5)P 2 appeared dependent on both intracellular and extracellular Ca 2ϩ . One of the mechanisms by which Ca 2ϩ is released into the cytoplasm to elicit contraction occurs through RyR channels located in the SR membrane (35). There are three molecularly distinct subtypes of RyR channels (RyR1, RyR2, and RyR3), and all three are present in the mouse aorta (24).…”

Imaging of Ca2+ Release by Caffeine and 9-Methyl-7-bromoeudistornin D and the Associated Activation of Large Conductance Ca2+-Dependent K+ Channels in Urinary Bladder Smooth Muscle Cells of the Guinea Pig

“…Moreover, MBED does not directly activate single BK channel (12). It has been suggested that Ca 2+ sparks originally occur in very narrow junctional spaces between discrete superficial SR fragments and plasmalemma (20,26,27). RyRs on the SR fragments are the target of caffeine and MBED (11,28).…”

Pharmacological Modulation of Sarcoplasmic Reticulum Function in Smooth Muscle

“…The distribution pattern of RyR follows that of the SR such that in where there is a patch distribution of SR in the cytoplasm, as in the guinea pig aorta, there is a sparse labeling with ryanodine markers, whereas tissues with a more prominent peripheral SR have a rich marking of RyR in the periphery-in other words, RyR distribution parallels that of the SR (Lesh et al, 1998). The physiological roles of RyR in smooth muscle cells are still being elucidated (Guerrero-Hernandez et al, 2002).…”