Degradation of atrial natriuretic peptide in dogs

To clarify the degradation of atrial natriuretic peptide (ANP) in dogs, plasma ANP concentrations in blood samples drawn from the coronary sinus, and in simultaneously collected blood samples of the arteries and veins of the lung, liver, kidney, spleen and cervix, and of the supramesenteric artery and the portal vein, were measured, both when infused with exogenous ANP (280 ng.kg-1.min-1, N = 7) and when not infused (N = 6). Venous ANP concentrations in most organs showed lower values than arterial levels by 11.6 to 33.6%, suggesting degradation during circulation. Exogenous ANP infusion resulted in a 26.0 to 41.9% arterio-venous decrease in ANP levels. These findings suggest that each organ contributes to ANP degradation, and that no specific organ plays a key role. The plasma ANP concentration was not reduced when blood samples were incubated for 60 min at 37 degrees C. The plasma from the coronary sinus and forearm vein contained essentially identical ANP molecular forms, as shown by gel permeation chromatography. Thus, the blood circulation through various organs does not cause high molecular weight ANP to be changed to other forms.