Clonidine normalizes low plasma beta-endorphin concentration and blood pressure in young men with mild essential hypertension.

In young men with mild essential hypertension and age-matched normotensive volunteers, plasma concentrations of the endogenous opioid beta-endorphin were determined hourly from 9:00 p.m. to 2:00 a.m. The hypertensive patients' mean plasma beta-endorphin concentration was significantly lower in comparison with normotensive controls. After 14 days of treatment with clonidine, systolic and diastolic blood pressure was significantly reduced in both groups. Plasma beta-endorphin concentration increased in the hypertensive patients, but remained unchanged in the normotensive volunteers. The present findings point to a possible involvement of reduced beta-endorphinergic activity in blood pressure regulation of young men with essential hypertension.