Elevated plasma catecholamines in young hypertensive and hyperkinetic patients: effect of pindolol.

The sympathetic nervous system plays an important role in the regulation of blood pressure. Plasma catecholamine concentrations are considered to be reliable indices of sympatho-neuronal (noradrenaline) and sympatho-adrenal (adrenaline) activity and reactivity in man. Sympathetic and adrenal activity and reactivity in young patients with essential hypertension or hyperkinetic heart syndrome were compared with an appropriate control group matched for age. The groups of hypertensive patients and patients with hyperkinetic heart syndrome could be clearly distinguished from control subjects on the basis of circulating catecholamine levels at rest. A clear-cut increase in circulating noradrenaline and adrenaline was observed in young patients with essential hypertension and hyperkinetic heart syndrome at rest. Clinically, hypertensive patients were characterized by elevated systolic and diastolic blood pressure and increased heart rate, whereas patients with hyperkinetic heart syndrome had increased heart rate and increased systolic blood pressure, whereas diastolic blood pressure was normal. At rest, there was a significant positive correlation between heart rate and circulating catecholamines in both groups of patients. In hypertensives a positive correlation between heart rate and plasma adrenaline concentrations, in patients with hyperkinetic heart syndrome a positive correlation between heart rate and plasma noradrenaline concentrations could be observed. In addition a positive correlation between plasma noradrenaline concentrations and systolic blood pressure in all groups of patients studied, was obtained. Sympatho-neuronal and sympatho-adrenal reactivity during mental stress or physical exercise increased in both groups of patients, mirrored by an increase in blood pressure and heart rate. Pindolol, a potent non-selective β-adrenoceptor blocking drug with intrinsic sympathomimetic activity and minimal membrane stabilizing properties, administered in a single oral dose of 10 mg, diminished the exaggerated sympathetic tone in both groups of patients by attenuating circulating catecholamine levels at rest or during mental stress, but not during physical exercise.