The influence of atherogenic diet on electromechanical coupling in rabbit myocardium

To characterize the role of the SR in the electromechanical coupling process in rabbit myocardium after a 12-week-long atherogenic diet containing cholesterol and oil, the influence of changes in Ca2e+ on isometric force, relaxation rate, and resting potentiation of isolated trabeculae were compared with 45Ca2+ binding and uptake by the SR. The diet produces a more strongly expressed resting potentiation of force at 1.25 and 2.5 mM Ca2e+ and an increase in the Vmax equivalent, the contractility index [(dF/dt)max/F'] and the relaxation index [-(dF/dt)max/F]. A higher Ca2e+-accumulating activity of heart microsomes from animals was observed after the diet. It is concluded that changes of SR function are involved in the mechanism responsible for modification of electromechanical coupling induced by cholesterol- and oil-containing diet.