title: Presence of functionally different compartments of the Ca2+ store in single intestinal smooth muscle cells.
abstract: Studies in smooth muscle bundles have shown the presence of functionally different compartments of Ca2+ store, one (S alpha) sensitive to both caffeine and inositol 1,4,5-trisphosphate (IP3), and the other (S beta) sensitive only to IP3. Ca2+ release in isolated single smooth muscle cells from guinea pig taenia caeci was studied to see if both compartments exist within a cell. Responses to caffeine and carbachol were consistently observed but were abolished after treatment with ryanodine, while intracellular application of IP3 induced Ca2+ release after the treatment, albeit smaller in size than control. Thus S alpha and S beta coexist in a single smooth muscle cell and agonist-induced Ca2+ release requires whole store to be loaded with Ca2+.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamazawa
authors.forename: M
authors.initials: M
authors.lastname: Iino
authors.forename: M
authors.initials: M
authors.lastname: Endo
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002451:Cell Compartmentation; D005453:Fluorescence; D006168:Guinea Pigs; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology
chemical_list: D012433:Ryanodine; D002110:Caffeine; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D002118:Calcium