Exercise increases the release of atrial natriuretic peptide in heart transplant recipients

It is known that atrial natriuretic peptide (ANP) is synthesized, stored and released from the myocytes of mammalian heart, but the role of cardiac autonomic nerves in triggering the release of ANP has not been fully assessed. We have therefore measured plasma ANP concentrations in the right atrium and the main pulmonary artery, together with pulmonary haemodynamics in 10 heart transplant (HT) recipients who underwent graded submaximal bicycle exercise during right-heart catheterisation. Pulmonary arterial blood samples and haemodynamic measurements were obtained at rest, on peak of exercise, and after ten minutes of recovery. A radioreceptor of alpha-human ANP was used to measure ANP levels. Exercise significantly increased ANP levels in both the right atrium from 24 pM (resting values) to 48.5 pM, and the main pulmonary artery from 27.1 pM (resting values) to 58.4 pM. We conclude that HT recipients still retain the ability to increase ANP release in response to graded submaximal dynamic exercise, and that the mechanisms underlying ANP release depend on other factors than the integrity of cardiac innervation in man.