THE PERICARDIUM ACTS AS A RESTRICTING FACTOR ON THE RELEASE OF ANF-(1-98) AND ANF-(99-126) AFTER VOLUME LOADING IN PIGS

The stimulus for secretion of the atrial peptides from the heart is a mechanical distension of the atria. We studied the changes in plasma l evels of immunoreactive ANF (1-98) and ANF (99-126) after volume loadi ng (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 sub jected to sham operation (peric+, n = 8). For irANF (99-126), the maxi mum 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 i ncrease 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 p mol/l to 1136.7 +/- 348.6 pmol/l (P < 0.05) in peric-. For both peptid es the maximal increase after loading was significantly greater when t he pericardium had been removed. The results demonstrate that the inta ct pericardium restricts peptide release secondary to volume infusion in closed-chest pigs.