Bioactivity of natriuretic peptide coinfusions; No evidence for unique effects of BNP in conscious sheep

Few studies have addressed the possibility chat brain natriuretic peptide ( BNP) possesses a profile of bioactivity that is distinct from that of atria l natriuretic peptide (ANP). Accordingly, we assessed the biologic actions of BNP in the setting of maximal or near-maximal ANP-induced biologic activ ity. Background ANP infusions (7.5 pmol/kg/min) administered on all study d ays, increased plasma ANP (similar to 120 pM) and cyclic guanosine monophos phate (GMP) levels (similar to 40 nM), and induced significant decreases in arterial pressure and cardiac output associated with increased heart rate, hematocrit, diuresis, and natriuresis. Increasing the dose twofold after 1 h (experiment 1, n = 5) showed no enhancement of these actions despite a f urther twofold increase in plasma ANP and cyclic GMP (both p values <0.001) . Addition of low-dose BNP (2 pmol/kg/min) after 1 h background infusion (e xperiment 2, n = 8), increased plasma BNP levels (30 pM, p < 0.001) but cau sed no significant effects on the hemodynamic, renal, or hormonal indices m easured. In conclusion, in the setting of maximal hemodynamic, renal, and e ndocrine responses to high-dose background infusions of ANP, coinfusion of BNP exhibits no enhancement of, or additional, biologic activity. This stud y provides no evidence for unique short-term biologic actions of ANP and BN P.