Capillary rarefaction characteristic of the skeletal muscle of hypertensive patients

Henrich, H; Romen, W; Heimgärtner, W.; Hartung, Erum A.; Bäumer, F

doi:10.1007/bf01713011

Cited by 96 publications

(49 citation statements)

References 17 publications

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“…Previous studies have demonstrated that human essential hypertension is characterized by an increased percentage of fast-twitch muscle fibers 61 -62 and a decreased vascularity of skeletal muscle. 63 In summary, the increased BP response in normotensive blacks appeared to be caused by an elevation in TPR. Blacks did not have increased venous plasma norepinephrine levels, suggesting that other factors (e.g., vascular structure or salt sensitivity) may have contributed to the increased resistance.…”

Section: Mabp=coxtprmentioning

confidence: 85%

Cardiovascular and plasma catecholamine responses to exercise in blacks and whites.

et al. 1992

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The purpose of the present study was to assess possible racial differences in cardiovascular and plasma catecholamine responses to dynamic exercise. A biracial group of normotensive college-age men (15 blacks, 15 whites) were tested for maximal oxygen uptake, resting blood pressure, and heart rate. Subjects then rode a cycle ergometer at 25%, 50%, and 75% of peak oxygen uptake (6 minutes at each stage). Blood pressure and heart rate were measured during supine rest, seated rest, and at each stage of exercise with an automated blood pressure monitor. At each stage, venous blood was sampled to allow determination of plasma norepinephrine and epinephrine, and cardiac output was measured with the carbon dioxide rebreathing technique. The results indicated that resting blood pressure was similar for blacks and whites (114/68 versus 115/68 mm Hg, respectively). Blacks exhibited greater systolic and diastolic blood pressures during submaximal dynamic exercise. However, blacks also showed a trend toward a positive parental history of hypertension, which has been associated with an increased pressor response. Racial differences did not exist for heart rate or cardiac output, but blacks had higher values for total peripheral resistance both at rest and during exercise. Although no overall racial differences were seen for plasma catecholamine concentrations at rest, blacks had significantly lower levels of norepinephrine (1,275 versus 1,556 pg/ml) and higher levels of epinephrine (306 versus 216 pg/ml) than whites at the highest work rate. The current study confirms the increased pressor response to exercise in normotensive blacks. Blacks had an elevation in total peripheral resistance that was not accompanied by an increase in plasma norepinephrine levels.

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Section: Mabp=coxtprmentioning

confidence: 85%

Cardiovascular and plasma catecholamine responses to exercise in blacks and whites.

et al. 1992

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“…38 Whether this association is independent of LTPA remains, however, unknown. Furthermore, compared with normotensive subjects, hypertensive subjects have a lower capillary density, 29,39 and the lower the capillary density, the higher the increase in BP from 50 to 70 years of age. 29 Other mechanisms explaining the low peripheral resistance may exist.…”

Section: Discussionmentioning

confidence: 96%

Muscle Fiber-Type Distribution as a Predictor of Blood Pressure

2005

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Abstract-The known association between physical activity and low blood pressure may be influenced by inherited characteristics. Skeletal muscle consists of type I (slow-twitch) and type II (fast-twitch) muscle fibers, with proportions highly variable between individuals and mostly determined by genetic factors. A high percentage of type I fibers (type I%) has been associated with low blood pressure in cross-sectional studies. We investigated whether type I percentage predicts future blood pressure levels and explains part of the association between physical activity and blood pressure. At baseline, in 1984, muscle fiber-type distribution, physical activity, and body mass index (BMI) were determined in 64 healthy men (age, 32 to 58 years). At follow-up, in 2003, blood pressure, physical activity, and BMI were determined in these men. In subjects without antihypertensive medication (nϭ43), type I percentage accounted for 5%/18% of the variation in systolic/diastolic blood pressure. A high type I percentage predicted, independent of both baseline (in 1984) and follow-up (in 2003), physical activity, BMI, and low systolic and diastolic blood pressure. Adjusted for all baseline covariates, a 20-unit higher type I percentage predicted a 11.6-mm Hg lower systolic blood pressure (Pϭ0.018) and a 5.0-mm Hg lower diastolic blood pressure (Pϭ0.018). High levels of physical activity in 1984 predicted low diastolic blood pressure, but this association was lost when type I percentage was included into the model. A high proportion of type I fibers in skeletal muscle is an independent predictor of low blood pressure and explains part of the known association between high levels of physical activity and low blood pressure. Key Words: blood pressure Ⅲ exercise Ⅲ hypertension Ⅲ muscles H ypertension, an important risk factor for cardiovascular diseases, 1,2 shortens life expectancy. 3,4 Low blood pressure (BP) levels and reduced risk for hypertension are associated with leisure time physical activity (LTPA) and fitness. 5-8 These associations may, however, be influenced by inherited characteristics.BP is the product of cardiac output and total peripheral resistance. 9 Peripheral resistance, and thus also BP, is influenced by the properties of skeletal muscle, more specifically its percentage of type I fibers (type I%). 10 Skeletal muscle consists of type I (slow-twitch) and type II (fast-twitch) muscle fibers. The type I% in the vastus lateralis muscle (the muscle most commonly studied) is highly variable between individuals, ranging from 13% to 96%, with a population mean of Ϸ50%, 11 and is mostly determined by genetic factors. 12 Type I fibers have a higher oxidative capacity than type II fibers. 13 Muscle fiber-type proportions differ between elite athletes in various types of sports. Endurance sports athletes have a high type I%, but speed and power sports athletes have a preponderance of type II fibers. 14 -16 In nonathletes as well, high, mainly endurance-type, LTPA levels are associated with a high type I%. 17,18 Former e...

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“…These data are seemingly contradictory to those reported by Baron et al [9], who found an inverse correlation between mean arterial blood pressure and leg blood flow using a pharmacological insulin infusion rate of 15 mU/kg × min in normotensive subjects. Whether this defect can be attributed to one or several of the abnormalities found in patients with essential hypertension such as excessive sympathetic activation [60], capillary rarefaction [61] or impaired endothelium-dependent vasodilatation [58,62,63], is currently unclear. Of interest in this respect is the study of Taddei et al [58] who measured both insulin-stimulated glucose uptake and endothelial function in patients with essential hypertension.…”

Section: Defects or Lack Thereof Of Insulin-induced Vasodilatation Imentioning

confidence: 99%

Insulin-induced vasodilatation: physiology or pharmacology?

1998

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Ever since the pioneering studies performed by Andres, Rabinowitz and Zierler 40 years ago [1±4], investigators interested in insulin action considered insulin resistance in obesity [3], hypertension [5], insulin-dependent (IDDM) [6] and non-insulin-dependent diabetes mellitus (NIDDM) [7] to be primarily a problem of glucose utilization in peripheral tissues, which was independent of glucose delivery. However, a series of studies published since 1990, notably by Alain Baron and his associates, demonstrated that under certain conditions insulin increased leg blood flow [8], and that defects in this action of insulin were likely to contribute significantly to insulin resistance of glucose uptake caused by obesity [8], hypertension [9], IDDM [10] and NIDDM [11]. These latter findings contradicted the vast majority of earlier data and created a controversy regarding the role, or lack thereof, of defects in insulin stimulated blood flow in the pathogenesis of insulin resistance of glucose uptake. It is the purpose of the ensuing review to try to discuss the reasons for the discrepant findings. We will first review a series of studies performed in our own laboratory, which were designed to resolve the ªflow controversyº. These studies examined whether the blood flow response to insulin is influenced by: i) the method used to quantitate blood flow; ii) the anatomical location of the flow measurement; iii) dose and duration of the insulin exposure; iv) individual factors such as limb muscularity, physical fitness and endothelial function, defined as the ability to vasodilate in response to nitric oxide (NO) synthesis-dependent vasodilatators. We will try to establish whether this physiological knowledge helps to explain the discrepancies observed in the studies performed in various insulin resistant conditions. We will then review the studies directly testing the hypothesis that an increase in blood flow enhances glucose uptake, and discuss the possibility that various vasoactive agents may change total flow similarly but have distinct effects on flow distribution. Finally, we will review studies relating insulin's vascular effects to endothelial function, which have opened up an entirely new perspective for understanding how insulin resistance might predispose to vascular disease. Determinants of insulin-induced vasodilatationMethodological aspects. Increases in blood flow by insulin have been reported under intravenously maintained normoglycaemic hyperinsulinaemic conditions using methods such as thermodilution [8,12] . Doppler ultrasound appears to be clearly less sensitive in detecting changes in flow. In our hands, 6 h of supraphysiological hyperinsulinaemia increased blood flow on average by 113 % when measured by venous occlusion plethysmography but only by 27 % when measured with Doppler ultrasound. The latter change was due to a 10 % increase in systolic peak flow velocity and an 18 % increase in heart rate. The insensitivity of the Doppler ultrasound technique may explain why Bu- Diabetologia (1998)

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Capillary rarefaction characteristic of the skeletal muscle of hypertensive patients

Cited by 96 publications

References 17 publications

Cardiovascular and plasma catecholamine responses to exercise in blacks and whites.

Cardiovascular and plasma catecholamine responses to exercise in blacks and whites.

Muscle Fiber-Type Distribution as a Predictor of Blood Pressure

Insulin-induced vasodilatation: physiology or pharmacology?

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