1. The pericardial fluid of 20 open heart surgery patients with acquired heart disease was analysed for atrial natriuretic peptide by radioimmunoassay.
2. The concentration of atrial natriuretic peptide in the pericardial fluid was significantly higher than in the corresponding plasma (316.8 ±50.0 versus 121.7 ± 29.1 pg/ml; P <0.01) and was higher in patients with congestive heart failure than in those without heart failure (469.3 ±78.6 versus 181.8 ± 26.7 pg/ml; P <0.001). Pericardial and plasma atrial natriuretic peptide concentrations showed a significant positive correlation. Pericardial fluid and plasma samples were fractionated using both reverse-phase high-performance liquid chromatography and gel permeation chromatography. Each fraction was assayed for atrial natriuretic peptide by radioimmunoassay, revealing the presence of β-atrial natriuretic peptide as well as α- and γ-atrial natriuretic peptide.
3. The pericardial fluid concentration of cyclic GMP, the intracellular second messenger for atrial natriuretic peptide, was significantly higher in patients with congestive heart failure than in patients without heart failure.