Organ extraction of atrial natriuretic peptide (ANP) in man. Significance of sampling site.

Arterial plasma immunoreactivity of endogenous human alpha-atrial natriuretic peptide (ANP) underwent mean 54%, 28% and 40% extraction during one passage through the circulation in the kidney (n = 12), liver-intestine (n = 14) and lower limb (n = 8), respectively, in supine fasting subjects with no detectable disease or subjects with cardiovascular or hepatic disorders of minor degree undergoing a haemodynamic investigation. No extraction was identified across the lungs as evaluated by the same concentration of ANP in pulmonary and femoral arteries (n = 7). The concentration of ANP in a superficial arm vein relative to the femoral artery varied considerably and extractions from 0% up to 58% were identified (mean 18%). The results suggest a high degree of, but only to some extent selective, extraction of ANP, which may account for its proposed short plasma half-life. Due to the different concentrations of ANP in various vascular beds, sampling site should be thoroughly specified.