Bronchodilator activity of atrial natriuretic peptide in guinea pigs

Atrial natriuretic peptide (ANP) produced concentration-dependent relaxation of isolated guinea pig tracheal chains contracted with histamine, serotonin, carbachol, and arachidonic acid. ANP was a full agonist. ANP was two- to three-fold less potent when compared with isoprenaline in relaxing histamine-, serotonin-, and arachidonic acid-contracted tracheal chains. However, ANP was 20-fold less potent than isoprenaline in relaxing carbachol-contracted tracheal chains. The relaxant potencies of isoprenaline and sodium nitroprusside were similar regardless of the agent used to induce the tone. ANP was less potent and efficacious than isoprenaline in inhibiting the serotonin-, histamine-, and carbachol-induced increases in pulmonary inflation pressure in pentobarbitone-anesthetized guinea pigs. Neither ANP nor isoprenaline inhibited the arachidonic acid-induced increase in pulmonary inflation pressure. ANP decreased and isoprenaline increased arterial pressure. The data suggest that ANP possesses limited bronchodilator activity especially in vivo.