Effects of alpha 1-blockade on maximal vascular conductance in young borderline hypertensives

This study was conducted to determine if reducing sympathetic tone with alpha 1-adrenergic receptor blockade affected the maximal forearm vascular conductance (FVCmax, reactive hyperemia) responses in young borderline hypertensives and normotensive controls. The FVC response following ischemia (14 min arterial occlusion with 3 min of hand exercise) was determined after systemic alpha 1-blockade (5 mg prazosin in preceding 24 h) in hypertensives (n = 11, MAP = 110 +/- 1, age = 24.5 +/- 1.1, mean +/- SEM) and normotensives (n = 13, MAP = 82 +/- 1, age = 22.5 +/- 0.3). During the placebo trial, resting FVC was lower in the hypertensives than the normotensives (.0472 +/- .0073 vs .0755 +/- .0095 units; P < .05). During alpha 1-blockade, FVC did not differ between the groups. Within each group, FVCmax did not differ significantly between either trial. During placebo, FVCmax was lower (P < .05) in the hypertensives (.3485 +/- .0335 vs .5641 +/- .0503 units) and remained so during alpha 1-blockade (.4048 +/- .0520 vs .5286 +/- .0275 units; P < .05). These data suggest that alpha 1-blockade does not increase FVCmax in borderline hypertensives and that both functional and structural changes in the peripheral vasculature are involved in the blood pressure elevations seen in this group.