Release of neuropeptide Y and noradrenaline from the human heart after aortic occlusion during coronary artery surgery

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Abstract
Study objective – The aim was to study the influence of complete myocardial ischaemia during aortic occlusion on release of neuropeptide Y and noradrenaline from the human myocardium. Design – Coronary sinus neuropeptide Y and noradrenaline were measured after 46(SEM 7) min of aortic occlusion with cold cardioplegia in patients undergoing coronary artery surgery. Patients – Seven patients (six male), aged 64(SEM 3) years, were studied. All were undergoing coronary artery bypass grafting. Measurements and main results – Reperfusion was associated with an increase in coronary sinus blood flow as determined by thermodilution. Simultaneously there was cardiac release of both neuropeptide Y and noradrenaline during the first two sampling periods: 3(0.6) and 7(0.6) min after the start of reperfusion. The outflow of neuropeptide Y and noradrenaline returned to preischaemic values by 14(1) min after reperfusion. Coronary sinus blood lactate and pyruvate concentrations were also increased at the start of reperfusion, while the lactate/ pyruvate ratio remained unchanged. Myocardial oxygen uptake was not influenced by cardiac ischaemia. Conclusions – Ischaemia of the human heart in vivo is associated with an enhanced outflow of neuropeptide Y and noradrenaline from the heart. Since arterial blood concentrations of these substances were also increased on reperfusion, their release is probably due to increased sympathetic nerve activity, though other mechanisms such as temperature change and local metabolite formation could also participate. Local release of neuropeptide Y during cardiac ischaemia may be involved in the regulation of coronary vascular tone as well as in the release of noradrenaline and acetylcholine.

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