[Calpains and cathepsin D from the damaged myocardium: the role of iodothyronines].

Experiments on albino male rats have demonstrated that a single subcutaneous isoprenaline injection produces cardiac calpaine activation and lysosomal labilization in euthyroidized animals. A 10 micrograms/kg triiodothyronine dose and a 50 micrograms/kg L-thyroxin inhibit calpaines and stabilize myocardial lysosomal membranes in intact rats. The effects following myocardial damage do not occur or become less pronounced in hyperthyroidism. Triiodothyronine proved to be more effective.