PLASMA ADRENOMEDULLIN IN PATIENTS WITH PRIMARY ALDOSTERONISM

Adrenomedullin (AM) is a novel hypotensive peptide originally isolated from the pheochromocytoma tissue of humans. To examine the pathophysi ological role of AM in primary aldosteronism (PA), the plasma concentr ation of AM in patients with PA was measured with a specific radioimmu noassay and compared to that in age- and sex-matched healthy normotens ive subjects. In addition, the concentrations of AM as well as catecho lamines in the plasma from both the adrenal vein and the inferior vena cava (IVC) were measured to determine whether or not the circulating AM in these PA patients is supplied from the adrenal medulla, which co ntains a much higher concentration of AM than any other human tissue d oes. The plasma concentration of AM in the PA patients (4.57 +/- 0.32 fmol/ml, n = 6) was significantly (P <.01) higher than that in the hea lthy subjects (3.06 +/- 0.20 fmol/mL, n = 12). A significant positive correlation (r = 0.62, P <.01) was observed between the mean blood pre ssure and the plasma AM level. The AM concentration in plasma from the adrenal vein was almost the same level as that from the IVC although the concentrations of both epinephrine and norepinephrine in the adren al vein were much higher than those in the IVC. Therefore, it seems un likely that the plasma AM in the PA patients is mainly supplied from t he adrenal medulla. Judging from the potent hypotensive activity of AM , the present findings suggest that AM participates in defense mechani sms acting against the elevation of blood pressure in the patients wit h PA.