NEUROPEPTIDE Y-LIKE IMMUNOREACTIVITY AND HYPERTENSION

Objective: Neuropeptide Y is a co-transmitter with noradrenaline in sympathetic neurons supplying arteries and veins with potent contractile effects. To investigate the role of neuropeptide Y in hypertension, we measured the circulating levels of neuropeptide Y and noradrenaline in patients with severe hypertension. Design: Samples were collected from patients with untreated, severe hypertension (diastolic blood pressure >120 mmHg) and in age- and sex-matched controls. After treatment with beta-adrenoceptor blockers, diuretics, angiotensin converting enzyme inhibitors or calcium antagonists, samples were taken from the patients during 12 months. Methods: The circulating levels of neuropeptide Y-like immunoreactivity (NPY-LI) were measured with a radioimmunoassay using a rabbit antiserum. Catecholamines were measured using high-performance liquid chromatography and electrochemical detection. Results: There was a significantly higher level of NPY-LI in the patients when they were compared with the controls. However, there was no correlation either in the controls or in the hypertensives between systolic blood pressure, diastolic blood pressure and NPY-LI or noradrenaline. The increased level of NPY-LI in plasma remained elevated for up to 12 months despite reduction in blood pressure to acceptable levels. The noradrenaline level was not increased before treatment, after 2-4 weeks or after 2-12 months treatment. Conclusion: The high level of NPY-LI may represent a marker for higher activity of the sympathetic nervous system which is not controlled by the treatment of blood pressure to normotension.