Cardiac myocytes express the cholecystokinin gene (CCK) at propeptide level. We recently reported that cardiac CCK expression is acutely regulated by isoprenaline in a porcine model. The regulation of CCK expression after myocardial infarction, in exercise, and in severe heart failure is, however, unknown. Cardiac tissue was obtained from healthy new-born and adolescent farm pigs. Myocardial infarction was induced by coronary artery occlusion in adult minipigs. Healthy male subjects performed a 3-hour exercise test, and patients with severe heart failure referred for right heart catheterization were included. Extracts of porcine cardiac tissue and human plasma were analysed with specific proCCK radioimmunoassays. Cardiac proCCK expression shifted from the right atrium in new-born piglets to include the left atrium in adolescent pigs. Regional proCCK expression in the adolescent pig heart was mainly confined to the atria without different expression in sinus node tissue. In adult minipigs with myocardial infarction, no changes in overall left ventricular function or proCCK expression were observed after 8 weeks. In healthy adults, proCCK in circulation increased markedly during exercise in parallel with pro-B-type natriuretic peptide. Finally, patients with severe heart failure displayed markedly increased proCCK – but not CCK – concentrations in plasma. Taken together, our data shows that regional proCCK expression reflects haemodynamic changes in the mammalian heart. The data supports the notion that cardiac CCK expression resembles that of cardiac natriuretic peptides in atria. The ventricular content of proCCK, however, differs from natriuretic peptides and suggests a distinct secretory pathway in ventricular cardiomyocytes.