Decreased vasodilator capacity of forearm resistance vessels in borderline hypertension.

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Abstract
Structural changes in resistance vessels were demonstrated in humans and animals with established hypertension; they may be present in the early and established stage of hypertension. To determine if there are structural vascular changes in humans with borderline hypertension, the vasodilator capacity of forearm resistance vessels were examined in 11 young borderline hypertensive men (25 .+-. 1 yr; mean .+-. SE), and 14 normotensive men (25 .+-. 1 yr). Vasodilator capacity was examined by measuring minimal vascular resistance during peak reactive hyperemia after release of 10 min of arterial occlusion. Resting forearm vascular resistance was not significantly different in borderline hypertensive (25.9 .+-. 1.8 units) and normotensive (21.6 .+-. 2.3 units) subjects. Minimal forearm vascular resistance after release of 10 min of arterial occlusion was 40% higher (P < 0.05) in borderline hypertensive (2.1 .+-. 0.2 units) than in normotensive (1.5 .+-. 0.1 units) subjects. Increasing the metabolic vasodilator stimulus by performing intermittent handgrip exercise during 10 min of arterial occlusion did not augment peak vasodilation; 10 min of arterial occlusion produced maximal vasodilation. Vascular resistance at peak vasodilation was not increased by lower body negative pressure, which suggests that neurogenic vasoconstriction did not limit peak reactive hyperemia. Forearem vasodilator capacity is limited in young men with borderline hypertension; there may be structural changes in forearm resistance vessels in borderline hypertension.