Cardiac C-type natriuretic peptide gene expression and plasma concentrations in neonatal piglets

Background: C-type natriuretic peptide (CNP) is a member of the natriuretic peptide family. Cardiac ANP and BNP expressions are firmly established, whereas CNP expression in the mammalian heart remains controversial. In the present report, we used a porcine model of the neonatal period with high expressions of cardiac ANP and BNP in order to elucidate the cardiac CNP expression profile. Methods: Plasma and cardiac tissue were obtained from newborn piglets during the first 72. h of life. The chamber-specific CNP mRNA contents were quantified by real-time PCR analysis. The proCNP concentrations in plasma and cardiac tissue extracts were quantified by a porcine-specific radioimmunoassay. Results: Cardiac CNP mRNA contents (n= 24) were low compared to sites of known expression, where porcine seminal vesicle CNP mRNA contents were 200-fold higher. In addition, plasma proCNP concentrations in the newborn piglets (n= 44) were exceedingly low compared to proANP concentrations (5.3. pmol/L (3.2-8.6) vs. 3438. pmol/L (2790-5418), p< 0.0001). The proCNP concentrations in atrial tissue extracts were barely detectable (≤ 0.06. pmol/g) (n= 2) compared to ventricular proANP (130. pmol/g (101-159)) and atrial proANP (12,303. pmol/g (10,623-15,412)). Conclusion: Our data show that the heart is not a major source of circulating proCNP in neonatal piglets.