Troponin I is a cardiac and skeletal muscle protein useful in the laboratory diagnosis of a heart attack. Troponin I is a part of the troponin protein complex, where it binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place.
SR-33805 is a calcium channel antagonist potentially for the treatment of atherosclerosis and heart failure. SR-33805 restored the MI-altered cell shortening without affecting the Ca(2+) transient amplitude, suggesting an increase of myofilament Ca(2+) sensitivity in MI myocytes. A SR33805-induced sensitization of myofilament activation was found to be associated with a slight increase in myosin light chain-2 phosphorylation and a more significant decrease on troponin I (TnI) phosphorylation. Decreased TnI phosphorylation was related to inhibition of protein kinase A activity by SR-33805.