Decreased capillary filtration but maintained venous compliance in the lower limb of aging women

Abstract

There are sex-related differences in venous compliance and capillary filtration in the lower limbs, which to some extent can explain the susceptibility to orthostatic intolerance in young women. With age, venous compliance and capacitance are reduced in men. This study was designed to evaluate age-related changes in venous compliance and capillary filtration in the lower limbs of healthy women. Included in this study were 22 young and 12 elderly women (23.1 Ϯ 0.4 and 66.4 Ϯ 1.4 yr). Lower body negative pressure (LBNP) of 11, 22, and 44 mmHg created defined transmural pressure gradients in the lower limbs. A plethysmographic technique was used on the calf to assess venous capacitance and net capillary filtration. Venous compliance was calculated with the aid of a quadratic regression equation. No age-related differences in venous compliance and capacitance were found. Net capillary filtration and capillary filtration coefficient (CFC) were lower in elderly women at a LBNP of 11 and 22 mmHg (0.0032 vs. 0.0044 and 0.0030 vs. 0.0041 ml ⅐ 100 ml Ϫ1 ⅐ min Ϫ1 ⅐ mmHg Ϫ1 , P Ͻ 0.001). At higher transmural pressure (LBNP, 44 mmHg), CFC increased by ϳ1/3 (0.010 ml ⅐ 100 ml Ϫ1 ⅐ min Ϫ1 ⅐ mmHg Ϫ1 ) in the elderly (P Ͻ 0.001) but remained unchanged in the young women. In conclusion, no age-related decrease in venous compliance and capacitance was seen in women. However, a decreased CFC was found with age, implying reduced capillary function. Increasing transmural pressure increased CFC in the elderly women, indicating an increased capillary susceptibility to transmural pressure load in dependent regions. These findings differ from earlier studies on age-related effects in men, indicating sex-specific vascular aging both in the venous section and microcirculation. capillary filtration coefficient; lower body negative pressure; age A TRANSITION FROM the supine to standing posture leads to a progressive pooling of blood in the compliant veins in the lower part of the body, which produces an immediate circulatory challenge due to the concomitant decrease in thoracic blood volume (5,6,39). Subjects with increased limb venous compliance have been shown to have greater orthostatic intolerance, probably due to an increased venous capacitance (24,36,46), although this relationship has recently been challenged by Hernandez and Franke (18). Venous compliance in the lower limbs decreases with age in men (33,38,39,49), but there is no reason to believe that venous compliance and capacitance are similar in men and women, since a sex difference has been established in young adults (26,30,34). Furthermore, age-related changes might be sex specific, in accordance with age-related changes of arteries, with women having a slower decrease in arterial compliance with age compared with men, an effect probably attributed to estrogen (9, 48). Estrogen has been shown to affect cellular transcription of elastin and collagen, and estrogen-receptors are known to exist in vascular smooth muscle cells (21,22,32).There is a marked capillary fluid filtratio...

Impaired compensatory response to hypovolaemic circulatory stress in type 1 diabetes mellitus

“…The control group (C) consisted of 12 healthy men (22 years, range [20][21][22][23][24][25]. The second group consisted of 12 type 1 diabetes patients without signs of microvascular complications (DMR-) (25 years, range [19][20][21][22][23][24][25][26][27][28], diabetes duration eight years (range 2-14), on good metabolic control (HbA1c 6.7 ± 1.0 %, reference value < 5.3%) on four-dose insulin regime without any other chronic medication. They had normal urinary albumin excretion, no retinopathy, no clinical symptoms or signs of peripheral or autonomous neuropathy, including normal tendon reflexes.…”

“…The technique is thoroughly described elsewhere. 20,21 Blood pooling is a rapid process, completed within 2 min at 30 cm H 2 O. 20,22 Coefficient of variation (CV%) for blood pooling with this technique is good (8%, separate study days).…”

“…20,22 Coefficient of variation (CV%) for blood pooling with this technique is good (8%, separate study days). 21 To assess the compensatory venous capacitance response and capillary fluid absorption in response to LBNP, changes in upper arm volume were measured by air plethysmography. 10,23 The air plethysmographs were cylindrical, made of transparent plastic, 8 cm long and with openings of different sizes to fit the subject's upper arm.…”

Lower capacitance response and capillary fluid absorption in women to defend central blood volume in response to acute hypovolemic circulatory stress

“…Almost exclusively, venous blood is pooled since the compliance of the arterial bed is only ϳ3% of that of the venous bed (40). Based on previously described technique and criteria, calf venous capacitance, compliance, and net capillary filtration were calculated (29,30). Furthermore, the time from the onset of LBNP to the development of 50% of maximal calf venous capacitance was defined (Cap 50).…”

“…Cardiovascular responses to LBNP seems to be unaffected by menstrual phase (5, 16), and, furthermore, venous compliance and capacitance do not change over the course of the menstrual cycle or with oral contraceptive use (36). Some data from the young women and men have been previously published (29,30). Each subject gave informed consent to the experiments, which were approved by the Ethics Committee of Linköping University (Linköping, Sweden).…”