Aims: In the present study we examined plasma and pericardial fluid ANP and BNP concentrations in postinfarction Ž . ventricular dysfunction. The association of peptide levels to left ventricular LV dysfunction and to the localization of the Ž . myocardial infarction MI was studied. Methods and results: Plasma and pericardial fluid samples were obtained from 37 patients undergoing coronary bypass surgery. According to the ECG and preceding coronary angiography, the patients were Ž .Ž . Ž . divided into three groups: previous anterior myocardial infarction MI n s 12 , previous inferiorrposterior MI n s 15 and Ž . no history of MI n s 10 . When compared to the control group with no MI, the patients with anterior MI had elevated Ž . plasma ANP and BNP 134 " 13 vs. 81 " 15 pgrml, P-0.01 and 95 " 10 pgrml vs. 26 " 8 pgrml, P-0.01, respectively and Ž . pericardial fluid BNP 473 " 60 pgrml vs. 57 " 8 pgrml, P-0.001 levels. The plasma natriuretic peptide concentrations were not increased in the patients with inferiorrposterior MI, but the pericardial fluid BNP concentrations were greater than in the Ž . patients with no history of MI 129 " 35 pgrml vs. 57 " 8 pgrml, P-0.05 . Six of the 12 patients with previous anterior MI had LVEFG 45%. Despite their normal LV systolic function, these patients had increased plasma and pericardial fluid BNP Ž levels when compared to the group with no history of MI 68 " 18 pgrml vs. 26 " 8 pgrml, P -0.05 and 534 " 258 pgrml vs.. 57 " 8 pgrml, P-0.01, respectively . Conclusions: Previous anterior myocardial infarction was associated with increased Ž . cardiac BNP production even if the LV systolic function was normal LVEFG 45% . The high pericardial fluid BNP concentrations in postinfarction patients suggest that the BNP synthesis and release are augmented in the ventricular myocardium independent from the LVEF. ᮊ

We determined concentrations and molecular sizes of natriuretic peptides in rat pericardial fluid and plasma by use of specific radioimmunoassays (RIA) and gel filtration HPLC. Our study shows that pericardial fluid forms a local extracellular storage of immunoreactive (ir) atrial natriuretic peptide (irANP) and brain natriuretic peptide (irBNP) near the heart where these peptides can be found in high concentrations in vivo. The concentrations of irANP, irBNP and NH2-terminal fragment of proANP (irNT-proANP) in pericardial fluid were 9.8 +/- 3.7, 0.49 +/- 0.47 and 28.9 +/- 11.8 nmol/l, respectively. IrBNP had the lowest (20 +/- 11) and irANP the highest (90 +/- 32) concentration ratio between pericardial fluid and plasma. The elution positions of irANP, irBNP and irNT-proANP in pericardial fluid and plasma were similar as examined by gel filtration HPLC. Furthermore, we show that the reduction of noradrenaline content of the heart muscle by reserpine reduces concentration of irANP in pericardial fluid by 39.6% and in plasma by 30.3% when compared to respective control group values. The concentration of irBNP is reduced by 44.1% in pericardial fluid but in plasma its reduction was not statistically significant. Vasoactive peptides released into the interstitial space and from there into pericardial fluid may have a more active role in the regulation of cardiac function than previously considered.