Stimulatory effect of dexamethasone on angiotensin-converting enzyme in neonatal rat cardiac myocytes

Angiotensin-converting enzyme (ACE) plays a central role in cardiac remodel ing associated with pathological conditions such as myocardial infarction. The existence of different cell types in the heart expressing components of the renin-angiotensin system makes it difficult to evaluate their relative role under physiological and pathological conditions. Since myocytes are t he predominant cellular constituent of the heart by mass, in the present st udy we studied the effects of glucocorticoids on ACE activity using well-de fined cultures of neonatal rat cardiac myocytes. Under steady-state conditi ons, ACE activity was present at very low levels, but after dexamethasone t reatment ACE activity increased significantly (100 nmol/l after 24 h) in a time-dependent fashion. These results demonstrate the influence of dexameth asone on ACE activity in rat cardiac myocytes. This is consistent with the idea that ACE activation occurs under stress conditions, such as myocardial infarction, in which glucocorticoid levels may increase approximately 50-f old.