ISSN:
1432-136X
Keywords:
Force of contraction
;
Action potential duration
;
Frequency-dependence
;
Intracellular calcium concentration
;
Mammalian Cardiac muscle
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The effect of action potential duration and elevated cytosolic sodium concentration on the forcefrequency relationship in isolated rabbit, guinea pig and rat papillary muscle preparations was studied. Shortening of action potential duration in guinea pig and rabbit from 150–200 ms to values characteristic of rat (20–40 ms), using the K(ATP) channel activator levkromakalim (15 μmol·l−1), markedly reduced the force of contraction and converted the positive force-frequency relationship into negative one at longer pacing cycle lengths. This conversion was greatly enhanced in the presence of acetylstrophanthidin (0.2–1 μmol·l−1), an inhibitor of the Na-K pump. Acetylstrophanthidin (1 μmol·l−1) alone, however, had no effect on the forcefrequency relationship. Prolongation of action potential duration in rat with inhibitors of cardiac K channels (4-aminopyridine [10 mmol·l−1] plus tetraethylammonium [2 mmol·l−1) increased the force of contraction and abolished the negative force-frequency relationship observed in rat at longer pacing-cycle lengths. It is concluded that both action potential duration and cytosolic sodium concentration are major determinants of the force-frequency relationship in mammalian myocardium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00301179
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