The functional and morphologic characteristics of isolated subcutaneous resistance vessels (about 170 fitn i.d.) from 15 untreated subjects with essential hypertension and 15 matched controls were examined. The vessels from the hypertensives had a 29% increase in the media-thickness-to-lumendiameter ratio. The maximal force development to noradrenaline (NA) expressed as active pressure (an estimate of the pressure the vessels could have contracted against in vivo) was 30 % higher in vessels from the hypertensives, while active media stress (force per square unit of smooth muscle) and sensitivity to NA was not significantly different. Increased active pressure, as well as unaltered active media stress and sensitivity, was seen for vasopressin, serotonin, angiotensin II, and K + . There was, however, an enhanced leftward shift of the NA sensitivity with cocaine (an inhibitor of the neuronal amine pump) in vessels from the hypertensives [pD 2 ( + cocaine) and pD 2 ( -cocaine) were 0.185 ± 0.053 and 0.040 ± 0.044, hypertensives and normotensives, respectively, p < 0.05] suggesting an abnormality of presynaptic function in essential hypertension. Furthermore, the calcium sensitivity was depressed (pD 2 was 4.197 ± 0.050 and 4.381 ± 0.068, hypertensives and normotensives, respectively, p < 0.05), and the rate of relaxation was faster (p < 0.05) in vessels from hypertensives, suggesting that excitation-contraction coupling might be depressed. The results suggest that the increased pressor response in essential hypertension can, to a large extent, be explained by altered vascular structure, while smooth muscle function is either unchanged or possibly depressed.

Background-This study compared the relative prognostic significance of 24 hour intra-arterial ambulatory systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and pulse pressure (PP) parameters in middle-aged versus elderly hypertensives. Methods and Results-A total of 546 subjects aged Ͻ60 years and 142 subjects aged Ն60 years who had undergone baseline pretreatment 24-hour intra-arterial ambulatory blood pressure monitoring were followed for 9.2Ϯ4.1 years. Multivariate analysis showed that in younger subjects, 24-hour, daytime, and nighttime DBP, MAP, and SBP, when considered individually, were positively related to morbid events; DBP parameters provided the best predictive values.In the group Ն60 years (elderly group), 24-hour, daytime, and nighttime PP and SBP were the most predictive parameters, whereas ambulatory DBP and MAP measurements failed to provide any prognostic value. When 24-hour values of SBP and DBP were jointly included in the baseline model, DBP (zϭ2.02, Pϭ0.04) but not SBP (zϭϪ0.43, Pϭ0.67) was related to outcome in younger subjects, whereas in the elderly group, SBP (zϭ3.33, Pϭ0.001) was positively and DBP (zϭϪ1.75, Pϭ0.07) was negatively related to outcome. Clinic blood pressure measurements failed to provide any independent prognostic value in either age group. Conclusions-The relative prognostic significance of ambulatory blood pressure components depends on age; DBP parameters provided the best prognostic value in middle-aged individuals, whereas PP parameters were the most predictive in the elderly. This may reflect differing underlying hemodynamic mechanisms of hypertension in these age groups.