Reduced beta-endorphin secretion in young patients with mild essential hypertension at rest and during exercise.

Evidence suggests that altered central adrenergic and opioidergic activities are involved in the elevated blood pressure of patients with essential hypertension. In the present study plasma concentrations of the opioid peptide beta-endorphin were significantly lower at rest in young subjects with essential hypertension and high plasma noradrenaline (n = 9) than in normotensive controls (n = 13, P less than 0.05). After bicycle exercise the beta-endorphin of both groups increased comparably, the percentage increase being greater in essential hypertensives than in controls. Treatment with clonidine for 14 days normalized low beta-endorphin, high plasma noradrenaline and high blood pressure in essential hypertensives at rest, but had no effect in controls. After bicycle exercise clonidine induced a threefold greater increase in beta-endorphin in controls than in essential hypertensives. The results point to a reduced endorphinergic activity in essential hypertensives, both at rest and during exercise, which can be normalized by central alpha 2-agonism at rest only. The results may indicate altered interactions between central adrenergic and opioidergic receptor systems, which could contribute to high blood pressure in essential hypertensives.