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The tension‐depolarization relationship of frog atrial trabeculae as determined by potassium contractures.
Author(s) -
Chapman R A,
Tunstall J
Publication year - 1981
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.1981.sp013539
Subject(s) - depolarization , tetracaine , tonic (physiology) , chemistry , biophysics , membrane potential , potassium , extracellular , muscle contracture , voltage clamp , contracture , anatomy , anesthesia , endocrinology , biochemistry , surgery , biology , medicine , organic chemistry , lidocaine
1. In the presence of extracellular Na ions K contractures evoked from isolated frog atrial trabeculae show an initial phasic and a subsequent tonic contractile response. 2. The phasic response shows a steep dependence on membrane potential, persists in Na‐free fluid, but is blocked by Mn ions, D600 and tetracaine. It has an indirect dependence on the [Ca]0 and would seem to be associated with both the secondary inward current and the release of Ca2+ from intracellular stores. 3. The tonic component of the K contracture is unaffected by D600 or tetracaine, shows a shallow dependence on membrane potential but is absent in Na‐free fluid. Its tension‐depolarization curve is immediately affected by alteration of either the [Ca]0 or the [Na]0. The form of the tension‐depolarization relationship and the effects of [Ca]0 and [Na]0 are consistent with the strength of the tonic tension being determined by a 3Na+ for 1Ca2+ exchange across the cell membrane. 4. The results agree well with those obtained previously with voltage‐clamp experiments on the same tissue, and may also help with the interpretation of Ca‐flux experiments.