Abstract-Alterations of structure and function of the microcirculation in hypertension in the elderly and changes with normotensive aging have not been fully clarified. We studied capillary pressure, density, and skin microvascular function in 46 subjects in 3 groups: elderly subjects (aged Ͼ60 years) with untreated hypertension (nϭ16), elderly normotensive subjects (nϭ16), and young normotensive subjects (age Ͻ45 years, nϭ14). In a subgroup of 19 subjects, we also studied resistance artery function in the isometric myograph. Capillary pressure was higher in both elderly groups (elderly hypertensives: 18.6Ϯ4.7 mm Hg, elderly normotensives: 17.6Ϯ4.0 mm Hg) compared with young normotensives (13.9Ϯ2.6 mm Hg, PϽ0.05), but capillary density did not differ between the groups. Skin vasodilating responses to acetylcholine were greater in young normotensives compared with both elderly groups (PϽ0.05). In isolated resistance arteries, there was a greater inhibitory effect from blockade of the L-arginine-NO pathway in elderly normotensives (PϽ0.05) and a reduction in the maximal inhibitory effect of combined blockade of NO, prostanoids, and endothelium-derived hyperpolarizing factor in elderly hypertensives (PϽ0.05). This study has demonstrated a significant effect of aging but no additional effect of hypertension on capillary pressure and no effect of either on capillary density. Our findings with both in vivo and in vitro methods suggest that normotensive aging may depend on relative preservation of NO-dependent vasodilatation in resistance arteries at the expense of a rise in capillary pressure. Key Words: microcirculation Ⅲ capillaries Ⅲ endothelium Ⅲ endothelium-derived relaxing factors Ⅲ aging A lterations of structure and function in the microcirculation are important factors in vascular disease states, such as hypertension and diabetes mellitus. 1 Capillary pressure is increased in essential hypertension, 2 and this may be because of decreased capillary numbers 3-5 or abnormalities in vascular responses at a precapillary or postcapillary level. 6,7 Both capillary rarefaction and abnormal microvascular responses have been observed before the development of clinical hypertension, 8,9 implicating these processes in pathogenesis.Aging is associated with endothelial dysfunction, possibly because of a decline in NO and prostanoid pathways, 10 -12 yet hypertension in the elderly is predominantly a systolic abnormality, 13 considered to be mainly because of altered large artery stiffness. 14 Whether microvascular structure and function is also abnormal in hypertension in the elderly has not been fully clarified. We, therefore, conducted the present study to examine whether aging, in the absence of changes in blood pressure (BP), is associated with abnormalities in the structure and function of the microcirculation, and whether, in older subjects, hypertension exacerbates any of the abnormalities observed. Methods Study SubjectsThe study was approved by the local research ethics committee and conducted according to the prin...

Alterations of structure and function of the microcirculation in hypertension in the elderly and changes with normotensive aging have not been fully clarified. We studied capillary pressure, density, and skin microvascular function in 46 subjects in 3 groups: elderly subjects (aged >60 years) with untreated hypertension (n=16), elderly normotensive subjects (n=16), and young normotensive subjects (age <45 years, n=14). In a subgroup of 19 subjects, we also studied resistance artery function in the isometric myograph. Capillary pressure was higher in both elderly groups (elderly hypertensives: 18.6±4.7 mm Hg, elderly normotensives: 17.6±4.0 mm Hg) compared with young normotensives (13.9±2.6 mm Hg, P <0.05), but capillary density did not differ between the groups. Skin vasodilating responses to acetylcholine were greater in young normotensives compared with both elderly groups ( P <0.05). In isolated resistance arteries, there was a greater inhibitory effect from blockade of the l -arginine-NO pathway in elderly normotensives ( P <0.05) and a reduction in the maximal inhibitory effect of combined blockade of NO, prostanoids, and endothelium-derived hyperpolarizing factor in elderly hypertensives ( P <0.05). This study has demonstrated a significant effect of aging but no additional effect of hypertension on capillary pressure and no effect of either on capillary density. Our findings with both in vivo and in vitro methods suggest that normotensive aging may depend on relative preservation of NO-dependent vasodilatation in resistance arteries at the expense of a rise in capillary pressure.

Abstract-Raised capillary pressure has been implicated in the formation of diabetic microangiopathy in type I diabetes, in which it is elevated in those with the earliest signs of diabetic kidney disease but remains normal in those without complications. In subjects with type 2 diabetes without complications, capillary pressure is normal, although alterations in the pressure waveforms suggested enhanced wave reflections. The nature of skin capillary pressure in subjects with type 2 diabetes and hypertension remains to be elucidated, as does the effect of blood pressure-lowering therapy on capillary pressure in these subjects. Three studies were performed in well-matched groups.

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