The atrial natriuretic factors (ANF) are peptide hormones first isolated from cardiac atrial tissue. l Related peptidic hormones, brain natriuretic peptide2 and~ rodilatin,~ have been identified. Many pharmacological actions have been demonstrated for ANF, most prominently vasorelaxant and natriuretic a~ tivities.~ The half-life of these peptides in circulation is quite with proteolytic cleavage occurring in several positions, 6 but ...