HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chapman, R. A. Search for Related Content PubMed PubMed Citation Articles by Chapman, R. A.

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]_o² 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 Ca²⁺ 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.

This article has been cited by other articles:

				L. Li and C. van Breemen Na+-Ca2+ Exchange in Intact Endothelium of Rabbit Cardiac Valve Circ. Res., March 1, 1995; 76(3): 396 - 404. [Abstract] [Full Text]