The role of epinephrine in essential hypertension

The effects of epinephrine (E) on plasma norepinephrine (NE) concentrations and cardiovascular responses before and after beta-blockade were studied in 36 patients with essential hypertension and 10 age-matched normal controls. The resting plasma NE and E were significantly higher in the borderline hypertensives (251 +/- 21 (SE) pg/ml, p less than 0.005; 57 +/- 5, p less than 0.05) than in normal controls (127 +/- 18; 38 +/- 7). An immediate rise in plasma E and NE was observed after one bolus intravenous administration of glucagon (1 mg). Then, plasma E fell rapidly to the baseline, whereas plasma NE declined much slowly. Propranolol did not affect the plasma E response to glucagon, but eliminated a prolonged rise of plasma NE. Exogenous E infusion (1.25-1.50 micrograms/min) for 30 min caused a definite rise in both plasma NE and blood pressures and lasted more than 30 min after termination of the infusion. Propranolol did not alter the time course of plasma E, but again inhibited a prolonged rise in both plasma NE and blood pressures. These findings support the view that plasma E can act physiologically as a sustained stimulator to the presynaptic beta-adrenoceptors, leading to an enhancement of NE release and a rise in blood pressure in man.