Premium
Tension‐dependent changes of the intracellular Ca2+ transients in ferret ventricular muscles.
Author(s) -
Kurihara S,
Komukai K
Publication year - 1995
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1995.sp021077
Subject(s) - extracellular , caffeine , contraction (grammar) , aequorin , intracellular , troponin c , chemistry , muscle contraction , biophysics , calcium , troponin , stimulation , tension (geology) , medicine , biology , biochemistry , materials science , organic chemistry , myocardial infarction , ultimate tensile strength , metallurgy
1. We measured the change in intracellular Ca2+ transients, using aequorin, in response to muscle length change during twitch contraction in ferret ventricular muscles. 2. Intracellular Ca2+ concentration ([Ca2+]i) was transiently increased when the muscle length was quickly shortened to 92% of maximum length (Lmax) at various times after stimulation (this increase in [Ca2+] is termed extra‐Ca2+). The magnitude of extra‐Ca2+, measured at different extracellular Ca2+ concentrations ([Ca2+]o), showed a dependence upon the magnitude of tension reduction and upon [Ca2+]i immediately before the length change. 3. In the presence of caffeine (5 mM), the difference between the Ca2+ transient at Lmax and at shorter lengths showed a time course similar to the difference between the developed tension at both lengths. A quick release in the caffeine‐treated preparation produced the extra‐Ca2+ with a slower time course compared with that observed in the absence of caffeine. Stretching the muscle from 96% Lmax to Lmax produced more active tension and decreased [Ca2+]i. 4. These results indicate that the affinity of troponin‐C, a major Ca2+ binding protein, which controls contraction, is influenced by developed tension i.e. cross‐bridge attachment and detachment.