Enhanced alpha-adrenoreceptor-mediated vasoconstriction in essential hypertension.

Forearm blood flow (FAF) has been determined using venous occlusion plethysmography in 24 patients with essential hypertension (EHT) and in 16 age-matched normotensive subjects (NT) under basal resting conditions, following nonspecific vasodilatation with sodium nitroprusside and after intraarterial infusion of the postjunctional alpha-blocking drug, prazosin. Under basal conditions, FAF was significantly higher in EHT than in NT. Infusion of sodium nitroprusside produced a similar absolute increase in FAF in both groups, whereas postjunctional alpha-blockade with prazosin led to a significantly greater increase in FAF in EHT than in NT. A positive correlation was found between plasma epinephrine concentration and prazosin-induced FAF in EHT but not in NT. These results suggest an enhanced postjunctional alpha-adrenoreceptor-mediated vasoconstrictor component in established EHT.