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The use of Ca‐transient to evaluate Ca 2+ utilization by myofilaments in living cardiac muscle
Author(s) -
Lookin Oleg
Publication year - 2020
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/1440-1681.13376
Subject(s) - myofilament , preload , isometric exercise , chemistry , contractility , biophysics , sarcomere , frank–starling law of the heart , medicine , myocyte , hemodynamics , biochemistry , biology , heart rate , stroke volume , blood pressure , myosin
The kinetics of Ca 2+ interaction with myofilaments is an important determinant of the preload‐dependent effects on myocardial contractility (the Frank–Starling Mechanism). However, the direct evaluation of this interaction in intact tissue is limited. To overcome this issue, the method of difference curve was proposed, which implements the subtraction of the referent Ca‐transient (measured in non‐stretched muscle) from the Ca‐transients measured at different preloads. This method was tested on the cardiac trabeculae of healthy (CONT) and monocrotaline‐treated rats (MCT), subjected to force–length protocol with simultaneous measurement of isometric twitch and Ca‐transient. The difference curve had two components, C2 and C3, which are distinct in their directions and, as hypothesized, may reflect mainly the kinetics of Ca 2+ utilization by and release from myofilaments, respectively. Both the components were quantitatively evaluated by their amplitude, integral magnitude and time‐to‐peak. The C3 component in either CONT or MCT was significantly higher in its amplitude/integral magnitude vs the C2 component, at any preload ( P < .05). The time‐to‐peak value was preload‐dependent only for the C3 component. There were tight relationships between the above characteristics of C2/C3 components and the characteristics of isometric tension (peak value, time‐to‐peak and the maximal rates of rise/decline) in CONT and MCT muscles. The C3 component was highly consistent with tension relaxation (Ca 2+ release from myofilaments), but the C2 component was partially consistent with tension development (Ca 2+ utilization by myofilaments). The novel method of the analysis of Ca‐transients can be utilized for indirect evaluation of Ca 2+ interaction with myofilaments in healthy and diseased myocardium.