The pericardium acts as a restricting factor on the release of ANF (1-98) and ANF (99-126) after volume loading in...

The stimulus for secretion of the atrial peptides from the heart is a mechanical distension of the atria. We studied the changes in plasma levels of immunoreactive ANF (1-98) and ANF (99-126) after volume loading (NaCl 0.9%, 50 ml/kg in 10 min) in pigs that had their pericardium opened (peric-, n = 8) and compared these changes to those of pigs subjected to sham operation (peric+, n = 8). For irANF (99-126), the maximum increase was achieved 10 min after the start of loading: 18.6 +/- 5.5 pmol/l to 31.4 +/- 15.6 pmol/l. (P < 0.05) in peric+ and 23.9 +/- 6.5 pmol/l to 110.2 +/- 46.2 pmol/l (P < 0.05) in peric-. The maximum increase in irANF (1-98) took place after 15 min: 658.8 +/- 223.9 pmol/l to 791.0 +/- 229.4 pmol/l (P < 0.05) in peric+ and 769.9 +/- 228.5 pmol/l to 1136.7 +/- 348.6 pmol/l (P < 0.05) in peric-. For both peptides the maximal increase after loading was significantly greater when the pericardium had been removed. The results demonstrate that the intact pericardium restricts peptide release secondary to volume infusion in closed-chest pigs.