Title
Ca(2+) spark sites in smooth muscle cells are numerous and differ in number of ryanodine receptors, large-conductance K(+) channels, and coupling ratio between them
UMMS Affiliation
Department of Physiology; Graduate School of Biomedical Sciences; Department of Cell Biology
Publication Date
2004-08-13
Document Type
Article
Subjects
Animals; Bufo marinus; Calcium; Calcium Signaling; Cytoplasm; Large-Conductance Calcium-Activated Potassium Channels; Microscopy, Fluorescence; Myocytes, Smooth Muscle; Patch-Clamp Techniques; Potassium Channels, Calcium-Activated; Ryanodine Receptor Calcium Release Channel; Sarcoplasmic Reticulum
Disciplines
Life Sciences | Medicine and Health Sciences
Abstract
Ca(2+) sparks are highly localized Ca(2+) transients caused by Ca(2+) release from sarcoplasmic reticulum through ryanodine receptors (RyR). In smooth muscle, Ca(2+) sparks activate nearby large-conductance, Ca(2+)-sensitive K(+) (BK) channels to generate spontaneous transient outward currents (STOC). The properties of individual sites that give rise to Ca(2+) sparks have not been examined systematically. We have characterized individual sites in amphibian gastric smooth muscle cells with simultaneous high-speed imaging of Ca(2+) sparks using wide-field digital microscopy and patch-clamp recording of STOC in whole cell mode. We used a signal mass approach to measure the total Ca(2+) released at a site and to estimate the Ca(2+) current flowing through RyR [I(Ca(spark))]. The variance between spark sites was significantly greater than the intrasite variance for the following parameters: Ca(2+) signal mass, I(Ca(spark)), STOC amplitude, and 5-ms isochronic STOC amplitude. Sites that failed to generate STOC did so consistently, while those at the remaining sites generated STOC without failure, allowing the sites to be divided into STOC-generating and STOC-less sites. We also determined the average number of spark sites, which was 42/cell at a minimum and more likely on the order of at least 400/cell. We conclude that 1) spark sites differ in the number of RyR, BK channels, and coupling ratio of RyR-BK channels, and 2) there are numerous Ca(2+) spark-generating sites in smooth muscle cells. The implications of these findings for the organization of the spark microdomain are explored.
DOI of Published Version
10.1152/ajpcell.00153.2004
Source
Am J Physiol Cell Physiol. 2004 Dec;287(6):C1577-88. Epub 2004 Aug 11. Link to article on publisher's site
Journal/Book/Conference Title
American journal of physiology. Cell physiology
Related Resources
PubMed ID
15306542
Repository Citation
Zhuge R, Fogarty KE, Baker SP, McCarron JG, Tuft RA, Lifshitz LM, Walsh JV. (2004). Ca(2+) spark sites in smooth muscle cells are numerous and differ in number of ryanodine receptors, large-conductance K(+) channels, and coupling ratio between them. Open Access Publications by UMMS Authors. https://doi.org/10.1152/ajpcell.00153.2004. Retrieved from https://escholarship.umassmed.edu/oapubs/110