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A study of the contractures induced in frog atrial trabeculae by a reduction of the bathing sodium concentration
Author(s) -
Chapman R. A.
Publication year - 1974
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.1974.sp010483
Subject(s) - muscle contracture , bathing , reduction (mathematics) , sodium , medicine , cardiology , anatomy , chemistry , pathology , mathematics , organic chemistry , geometry
1. The relationship between the [Ca] o , the [Na] o and the strength of the contracture evoked when the [Na] o is reduced has been investigated in isolated frog atrial trabeculae. 2. The strength of the contracture varies by the [Ca] o 2 and by 4√([Na] o ) over the lower tension range. 3. The contracture induced by reduction of [Na] o is not sustained, but relaxes spontaneously. The rate of this relaxation is only dependent on the [Na] o is the presence of strophanthidin. 4. After the spontaneous relaxation of an Na‐free contracture, the ability of the trabecula to develop tension upon a second challenge with Na‐free solution returns in about 3 min if the muscle is perfused with Na‐containing fluid. This recovery process is slowed if the [Na] o is low during the recovery period, but the recovery is hastened by electrical stimulation of the preparation or by perfusion with K‐free or strophanthidin containing sodium‐Ringer. 5. It is suggested that the influx of Ca 2+ which induces the Na‐free contracture depends on the presence of Na + inside the cells. When the intracellular Na concentration falls, the Ca influx falls, and the muscle relaxes as a result of the activity of an intracellular relaxing structure.