Hemodynamic, hormonal, and renal actions of adrenomedullin-2 in normal conscious sheep

Although blood pressure and heart rate effects have been reported for adrenomedullin 2 (AM-2), a new member of the calcitonin gene-related peptide superfamily, little information is available regarding other biological actions of systemically administered AM-2. Accordingly, we report for the first time the integrated hemodynamic, hormonal, and renal actions of the AM-2 in normal conscious sheep. AM-2 induced significant reductions in mean arterial pressure (P < 0.001). This was associated with dose-dependent rises in heart rate (P < 0.001) and cardiac output (P < 0.001) and dose-dependent falls in calculated total peripheral resistance (P < 0.001). Right atrial pressure was increased post infusion (P = 0.026), whereas hematocrit fell post infusion (P = 0.001). AM-2 also induced significant hormonal changes, particularly in the renin-angiotensin-aldosterone system where plasma renin activity was significantly activated (P < 0.001) associated with a dose-dependent rise in plasma aldosterone (P < 0.001). Plasma cAMP also rose in response to AM-2 (P < 0.001), as did circulating levels of the natriuretic peptides, particularly post infusion. In conclusion, iv infusions of AM-2 administered to normal conscious sheep induced significant hemodynamic actions including reduced mean arterial pressure and calculated total peripheral resistance and increased heart rate and cardiac output. Concurrently, AM-2 activated plasma cAMP, plasma renin activity, aldosterone, and the natriuretic peptides. With the exception of actions on aldosterone, these actions are similar to those previously reported for AM. Thus, AM-2 may be another important regulator of volume and pressure homeostasis and may play a role in the pathophysiology of heart disease.