[Disruption of chemomechanical coupling in cardiomyocyte myofibrils in L-tyroxine toxicosis and athyreosis].

Skin assay of dog myocardial fibers showed alterations in free energy of ATP hydrolysis correlated distinctly with the rate of activity generated by the fiber (r = 0.87; P < 0.01). Impairment of chemomechanical coupling occurred in the system of myocardial contractile proteins under conditions of athyreosis and L-thyroxin-induced toxicosis, which is responsible for qualitative and quantitative deteriorations of energy transformation in cardiomyocyte myofibrils. The sites of energy generation and liberation appear to be spatially disconnected in the active actomyosin complex and their coupling and uncoupling is related to properties of actin.