[The calcium metabolism of myocardial mitochondria and sarcoplasmic reticulum in experimental potassium deficiency (author's transl)].

Mechanical Parameters of the whole, Langendorff-perfused cat heart and of isolated right ventricular papillary muscles are depressed in chronic potassium deficiency. 45Ca binding of sarcoplasmic reticulum (SR) was found to be diminished and correlated with a reduced contractility of the perfused hearts. 45Ca uptake of sarcoplasmic reticulum isolated from potassium deficient hearts was also reduced. The mitrochondrial 45Ca binding and endogenous Ca concentration were increased and there was a positive correlation between these two parameters. The data suggest that a reduced SR Ca binding plays a role in the depression of myocardial contractility in chronic potassium deficiency. Increased mitochondrial 45Ca binding in the presence of reduced 45Ca binding and uptake of sarcoplasmic reticulum suggests the possibility that mitochondria are an additional myocardial calcium pool in chronic potassium deficiency.