A single luminally continuous sarcoplasmic reticulum with apparently separate Ca2+ stores in smooth muscle.
Whether or not the sarcoplasmic reticulum (SR) is a continuous, interconnected network surrounding a single lumen or comprises multiple, separate Ca2+ pools was investigated in voltage-clamped single smooth muscle cells using local photolysis of caged compounds and Ca2+ imaging. The entire SR could be depleted or refilled from one small site via either inositol 1,4,5-trisphosphate receptors (IP3R) or ryanodine receptors (RyR) suggesting the SR is luminally continuous and that Ca2+ may diffuse freely throughout. Notwithstanding, regulation of the opening of RyR and IP3R, by the [Ca2+] within the SR, may create several apparent SR elements with various receptor arrangements. IP3R and RyR may appear to exist entirely on a single store, and there may seem to be additional SR elements that express either only RyR or only IP3R. The various SR receptor arrangements and apparently separate Ca2+ storage elements exist in a single luminally continuous SR entity.
McCarron
John G
JG
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 27 Taylor Street, Glasgow G4 0NR, Scotland, United Kingdom. john.mccarron@strath.ac.uk
Olson
Marnie L
ML
D000818:Animals; D001665:Binding Sites; D001896:Boron Compounds / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004594:Electrophysiology; D006168:Guinea Pigs; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D007477:Ions; D008297:Male; D008954:Models, Biological; D009130:Muscle, Smooth / Q000378:metabolism*; D010782:Photolysis; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007477:Ions; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium