[Composition of the titin isoforms in muscles in pathology].

An electrophoretic study of changes in the composition of titin isoforms in skeletal and cardiac muscles of human and rat in pathology has been carried out. A more considerable decrease in the content of intact titin isoforms in comparison with the content of N2BA- and N2B-titins in hypertrophic heart of spontaneously hypertensive rats, N2A-titin in back muscle from patients with the "stiff-man syndrome", and in m. soleus of human and rats during the development of "muscle hypogravity syndrome" has been observed. In the last case, the relation between the reduction of titin content in m. soleus and the increase in the time the rats were in conditions of simulated microgravity has been revealed. On electrophoregrams of the left ventricle myocardium of patients with the terminal stage of dilated cardiomyopathy, intact titin and N2BA-titins were absent, and a considerable decrease in the content of N2B-titins has been observed, which could be a consequence of the terminal stage of pathology. Our results show that the development of the diseases is accompanied by a greater destruction of intact titin than of its other forms, which may be important for diagnostics of the pathological process.