PMID: 1209015Jan 1, 1975Paper

Time course of mechanical activity in mammalian cardiac muscle: dependence on species, loading, and displacement

Recent Advances in Studies on Cardiac Structure and Metabolism
R Bodem, E H Sonnenblick

Abstract

We have found that animal species is of great importance when mechanics of contraction are analyzed in mammalian cardiac muscle. Mechanics of contraction have been studied comparatively in the isolated papillary muscles of the rat, cat, and rabbit under control conditions and following alterations of loading and inotropic interventions. The time course of the shortening ability measured in terms of the velocity of shortening at constant contractile element length and load following quick releases to preload peaked at 20, 30, and 70% of time to peak force (TPF) in the rat, cat, and rabbit, respectively, and declined more slowly in the rabbit. The shortening ability peaked progressively later in contraction at increasing loads in the cat, but not in the rabbit. Shortening ability measured after releases to zero load or after imposing "load clamps" of variable magnitude and duration reached the maximum much later in the rabbit than in the cat. The contractile response to changes of the contraction mode from isometric to isotonic was different in cat and rabbit. Upon increase in the stimulation rate from 6 to 60/min, force increased to a greater extent in the rabbit than in the cat, while TPF did not decrease in the rabbit as seen ...Continue Reading

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