[Subcellular basis of disorders of the contractile capacity of the heart in L-thyroxine-induced thyrotoxicosis].

In experiments on dogs, the authors examined the functional activity of three cardiomyocyte systems responsible for contraction-relaxation (the systems of contractile proteins, calcium transport and energy supply) in the dynamics of L-thyroxine-induced toxicosis. A fall in the capacity of the contractile protein system to generate energy and to perform was shown to play the leading role in decrease of myocardial reserve forces and reduction in cardiac contractility. There was a drop in the intensity of calcium transport through the membranes of the sarcoplasmic reticulum and mitochondria and a deficiency of the direct energy source for contraction only in the late period of the disease.

[Intracellular Ca2+ transport in the dog myocardium during experimental informational neurosis].

Intracellular calcium transport in the myocardium has been studied in dogs with experimental informational neurosis. It has been shown that in such dogs, the Ca-accumulating ability of the sarcoplasmic reticulum and mitochondria was significantly reduced. At the same time the content of endogenous Ca2+ in the intracellular structures under consideration remained unchanged.

[Mechanical activity of the system of contractile proteins, energy supply of the myocardium and disruption of calcium transport in inflammatory lesions of the myocardium].

In rabbit experiments it has been shown that in toxico-allergic myocarditis the disordered utilization of ATP energy is responsible for acute insufficiency of the myocardial contractile function, which results in a marked energy deficiency due to mitochondrial damage, the Ca2+ absorbtion and binding by the fragmented sarcoplasmatic reticulum being diminished.

[Effect of calmodulin and 3':5'-AMP-dependent protein kinases on calcium transport by sarcoplasmic reticulum of normal rabbit myocardium and in toxico-allergic myocarditis].

It was demonstrated that under normal conditions calmodulin and exogenous 3':5'-AMP-dependent protein kinase considerably active Ca2+ transport by sarcoplasmic reticulum of rabbit myocardium; a combined action of these compounds produces an additive effect. The protein-inhibitor of 3':5'-AMP-dependent protein kinase and trifluoroperazine eliminate the activating effect of 3':5'-AMP-dependent protein kinase; in addition, trifluoroperazine decreases significantly the basal level of Ca2+ uptake. The 3':5'-AMP-dependent activation of Ca2+ transport becomes apparent after Ca2+-calmodulin-dependent phosphorylation of FSR membrane proteins.