Free calcium at rest during "catch" in single smooth muscle cells.
Tension and intracellular free calcium concentration [( Ca2+]i) were measured simultaneously in single smooth muscle cells isolated from the anterior byssus retractor muscle (ABRM) of Mytilus edulis that were loaded with the fluorescent Ca2+ indicator fura-2. Electrical stimulation evoked a transient elevation of [Ca2+]i associated with a "catch" contraction. During the catch state, however, [Ca2+]i was effectively at its resting level and was unaffected by 5-hydroxytryptamine, which induced a rapid relaxation from catch. The results indicate that a maintained high [Ca2+]i is not required for the maintenance of catch tension in intact ABRM and that there was no significant change in [Ca2+]i upon abolition of catch.
Ishii
N
N
Zoological Institute, Faculty of Science, University of Tokyo, Japan.
Simpson
A W
AW
Ashley
C C
CC
D000818:Animals; D001572:Benzofurans; D049872:Bivalvia; D002118:Calcium / Q000502:physiology*; D005456:Fluorescent Dyes; D016257:Fura-2; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology*; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods
D001572:Benzofurans; D005456:Fluorescent Dyes; D002118:Calcium; D016257:Fura-2