[Phosphorylation of phospholamban in experimental myocardial infarction and proteolysis stabilization during phosphorylation].

The cAMP-dependent phosphorylation of proteins of both non-fractionated microsomes of the dog myocardium and phospholamban were studied in experimental myocardial infarction. In the presence of cAMP and exogenous protein kinase, the incorporation of 33P into microsomes and phospholamban of the affected muscle decreased as compared to that in the intact heart muscle. During infarction, partial degradation of phospholamban was observed. At the same time there was an increase in endogenous proteinase activity in microsomes of the affected muscle. The phosphorylation of phospholamban combined with its treatment by trypsin was investigated. The data indicate the correlation between the degree of phospholamban phosphorylation and its proteinase resistance in both the affected and intact myocardium.