A comparison of the vasodilator responses to atrial peptides in the pulmonary and renal arteries of the pig in vitro.

Noradrenaline preconstricted pulmonary and renal artery segments from 20 large White pigs were examined in vitro for their responses to alpha-human atrial natriuretic peptide (alpha-hANP), rat-atriopeptin I (AP I) or rat-atriopeptin III (AP III) added in a cumulative manner. The role of the vascular endothelium in atrial peptide-induced relaxation was examined in the presence of indomethacin and propranolol by removal of the endothelium in one of a pair of arterial segments. Pulmonary artery was significantly (P less than 0.001) more sensitive than renal artery to alpha-hANP with a potency ratio of approximately 10. alpha-hANP appeared to be a more potent relaxant than AP III and AP I in pulmonary artery. Potency ratios were approximately 2 (AP III vs alpha-hANP; P less than 0.05) and 30 (API vs alpha-ANP; P less than 0.001). Removal of the endothelium increased the sensitivity of renal artery to a alpha-hANP, but made no difference to the pulmonary arterial relaxations. In man the highest circulating concentrations of ANP are found in the pulmonary artery. The demonstration of its potent relaxant effects at this site in the pig indicates a possible role in the modulation of pulmonary arterial tone.