Plasma concentrations of ?-endorphin (?-EP), leucine enkephalin (L-EK), neurotensin (NT), arginine vasopressin (AVP), renin activity (PRA) and angiotensin Ⅱ (AT Ⅱ ) were measured by radioimmunoassay in 60 normal persons and 120 hypertensive patients. There were lower levels of ?-EP and L-EK (P