Vasorelaxant and natriuretic activities of synthetic atrial peptides

The vasorelaxant and natriuretic activities of synthetic atrial natriuretic peptides (ANF) were compared by measuring relaxation of histamine-contracted rabbit aortic rings and changes in urinary sodium excretion in anesthetized rats. The peptides studied and their relation to pro-ANF were: atriopeptins (AP) I, II and III (ANF 103-123, 103-125, 103-126), cardionatrin (CN) (ANF 99-126), alpha-human atrial natriuretic polypeptide (alpha-hANP) (human 99-126) and a fragment of the last (hFrag) (human ANF 105-126). The concentration causing 50% relaxation (EC50) in the vasorelaxant assay for API was greater than that of the other peptides (p less than 0.05). The EC50 for hFrag was 20 times greater than that of alpha-hANP, but this difference was not statistically significant. API caused less natriuresis compared with the other peptides (p less than 0.05). The natriuresis induced by CN was significantly greater than that of the other peptides at the 485 pmol dose. These results indicated that, except for API, the peptides studied has similar vasorelaxant and natriuretic activities.