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CHANGES IN CARDIAC CONTRACTILITY EVOKED UNDER ISOTONIC AND ISOMETRIC CONDITIONS
Author(s) -
Nayler Winifred G
Publication year - 1961
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1961.44
Subject(s) - isometric exercise , contractility , stimulation , isotonic , medicine , calcium , toad , cardiac muscle , bufo marinus , heart rate , chemistry , anatomy , cardiology , endocrinology , biology , blood pressure
SUMMARY Isolated ventricles or ventricular strips from winter toads ( Bufo marinus ) were used to study changes in contractile behaviour of cardiac muscle under isometric and isotonic conditions. Variations in the stimulation rate and in the Na+ and Ca++ concentrations of the perfusate were used to induce changes in contractility. The changes recorded isotonically differed from those recorded isometrically. The optimum stimulation frequency was different in the two preparations but the rate at which the various responses were produced depended to some extent upon the stimulation rate used. The results are discussed in relation to the hypothesis that stimulation and stretch influence calcium exchangeability.