[Relation between myocardial cAMP and renin-angiotensin system activation after acute pressure overload]

In order to investigate the relationship between cAMP and myocardial renin-angiotensin system activation after acute pressure overload, an animal model of acute pressure overload was established by constriction of abdominal aorta. It was found that angiotensin converting enzyme (ACE) mRNA and protein expression were increased markedly, ACE activity and angiotensin II content were also elevated significantly in rat heart 1 h after acute pressure overload, and the increases were kept at high level. Meanwhile the myocardial cAMP concentration was increased significantly at 0.5 h, reached the peak at day 5, and returned to normal at day 30 after operation. Then cardiomyocytes were cultured to observe whether ACE gene expression can be induced by cAMP. The results showed that elevation of cAMP content in cultured cardiomyocytes stimulated by isoproterenol (ISO, 0.01 micromol/L) increased ACE mRNA and protein expression, and also increased ACE activity and Ang II content in cultural medium. These results suggest that cAMP plays a role in the mechanism of activation of myocardial renin-angiotensin system induced by pressure overload.