Chromogranin A in the mammalian heart: expression without secretion

Abstract

Aim: To investigate whether chromogranin A (CgA) is secreted from the heart into circulation. Materials & methods: Porcine cardiac tissue was analyzed for the presence of CgA-derived glycopeptides using a global O-glycoproteomic strategy. Blood was sampled from the femoral vein, right atrium, coronary sinus and the left atrium from patients with predominantly atrial disease. The local concentration of proatrial natriuretic peptide and CgA was measured with immunoassays. Results: We identified CgA-derived glycopeptides exclusively in the atrial tissue. Proatrial natriuretic peptide is secreted from the heart (coronary sinus [795 pmol/l] vs left atrium [678 pmol/l]; p < 0.01) whereas no CgA gradient across the heart could be established (p = 0.6366). Conclusion: The cardiac atria express but do not secrete CgA into circulation in patients with atrial disease.