Brain natriuretic peptide is cosecreted with atrial natriuretic peptide from porcine cardiocytes

Using primary cultures of atrial cardiocytes from neonatal pig, the secretion brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP)-like immunoreactivities (LI) was studied in vitro. Porcine cardiocytes time-dependently secreted both BNP-LI and ANP-LI into medium under a serum-free condition, although the amount of BNP-LI secreted was about one-third that of ANP-LI. Phorbol ester and Ca2+ ionophore had less stimulatory effects on secretion of BNP-LI than that of ANP-LI. Reverse-phase HPLC of the conditioned medium revealed a single major BNP-LI component corresponding to synthetic porcine BNP(1-26). These data suggest that a small molecular weight form BNP, possibly BNP(1-26), is cosecreted with ANP from porcine cardiocytes.