Almerina Biggi

Assessment of flow-mediated dilation reproducibility: a nationwide multicenter study

Objective: Impaired flow-mediated dilation (FMD) is associated with cardiovascular risk factors and provides prognostic information. Despite the noninvasive nature of this technique, a major limitation to its widespread use is low reproducibility. The aim of this study was to evaluate impact of methodological standardization among different investigation sites on brachial artery FMD reproducibility. Methods: Seven Italian centers recruited 135 healthy volunteers, aged 20–60 years. FMD was assessed by high-resolution ultrasound equipped with a stereotactic probe-holding device. Certified sonographers recorded brachial artery scans at baseline (day 1a), 1 h after (day 1b), and 1 month later (day 30). Endothelium-independent vasodilation (EIVD) to sublingual glyceril-trinitrate was recorded at day 1 and day 30. FMD and EIVD were blindly evaluated at the coordinating center by an automated edge detection system. The intra-session (day 1a versus 1b) and inter-session (day 1a versus 30) coefficients of variation were calculated. Results: FMD was not significantly (P = 0.91) different at day 1a, day 1b and day 30 (6.52 ± 2.9, 6.42 ± 3.1, 6.57 ± 2.8%, respectively). The FMD intra-session coefficient of variation was 9.9 ± 8.4% (from 7.6 to 11.9% across centers). The FMD inter-session coefficient of variation was 12.9 ± 11.6% (from 11.6 to 16.1% across centers). Inter-session coefficient of variation for EIDV was 19.7 ± 16.8%. Conclusions: This study shows a homogeneous coefficient of variation for FMD among different centers. The inter-session coefficient of variation was similar to the intra-session coefficient of variation, representing the intrinsic FMD variability. We demonstrate for the first time that rigorous and standardized procedure may provide reproducible FMD assessment to study endothelial function in multicenter clinical trials.

Endothelin-A Blockade Attenuates Systemic and Renal Hemodynamic Effects of L-NAME in Humans

Eight Na-repleted volunteers underwent 3 separate 90-minute infusions of either N(G)-nitro-L-arginine methyl ester (L-NAME) 3.0 mg. kg(-1). min(-1) or endothelin-A receptor (ET-A) blocker BQ-123 (BQ) 0.125 nmol. kg(-1). min(-1) or both. Mean arterial pressure (MAP), glomerular filtration rate (GFR), renal blood flow (RBF), renal vascular resistances (RVR), and sodium excretion rate (UNaV) were measured at baseline (b) and from 0 to 45 minutes (period 1) and 45 to 90 minutes (period 2) of infusion. BQ alone had no effect. GFR declined by 4.9% (P<0.001 versus b) in period 1, to 9.9% (P<0. 001) in period 2 with L-NAME, and by 3.3% (P<0.01) to 6.6% (P<0.001) with L-NAME plus BQ (P=NS between L-NAME and L-NAME plus BQ). UNaV fell equally with L-NAME or L-NAME plus BQ. MAP rose significantly in period 2 with L-NAME (6.9%; P<0.001) but not with coinfused BQ (2. 1%; P=NA versus b, P=0.005 versus L-NAME alone). RBF declined by 12. 2% (P<0.001) to 18.3% (P<0.001) with L-NAME and by 4.6% (P<0.005) to 8.2% (P<0.001) with L-NAME plus BQ. These changes were smaller with L-NAME plus BQ (P<0.05 in period 1 and P<0.02 in period 2). Blunted changes were also seen for RVR (P<0.005 in period 1 and P<0.001 in period 2 between L-NAME alone and L-NAME plus BQ). These findings show that systemic and renal vasoconstriction due to L-NAME are attenuated by BQ, which suggests that an interaction between endogenous nitric oxide production and ET-A activity participates in the maintenance of baseline systemic and renal vascular tone in humans.

Endothelial dysfunction and cardiovascular risk profile in long-term withdrawing alcoholics.

Background Rates of cardiovascular morbidity and mortality are greater in heavy alcoholics than in either teetotallers or light-to-moderate drinkers. Objective On the assumption that factors leading to atherosclerotic damage remain operative even after long-term alcohol withdrawal, we studied the possible mechanisms of raised cardiovascular risk in former heavy alcoholics. Methods Forty-two apparently disease-free, normotensive alcoholics detoxified for 37.1 ± 31.9 (SD) months, median 24, participated in the study. They were compared with 39 lifetime alcohol-abstaining control subjects, carefully matched for age, sex, body mass index, smoking and dietary habits, physical activity, lipids and fasting glucose. Endothelial function (flow-mediated dilation of brachial artery, high-resolution ultrasound technique), blood pressure, and some parameters of endothelial activation, oxidative stress, vascular inflammation and insulin sensitivity were measured. Results The maximal percentage of flow-mediated dilatation was reduced in detoxified alcoholics (10.1 ± 4.6 versus 14.9 ± 7.4, P < 0.001) who also showed significantly higher blood pressure (systolic 127.5 ± 12.9 versus 118.2 ± 10.7 mmHg, P < 0.001; diastolic 79.4 ± 7.1 versus 74.6 ± 6.4 mmHg, P < 0.01; mean 95.4 ± 8.2 versus 89.1 ± 7.3 mmHg, P < 0.001), uric acid (5.0 ± 1.1 versus 4.4 ± 0.8 mg/dl, P < 0.05), high-sensitivity C-reactive protein (2.1 ± 2.0 versus 1.0 ± 0.9 mg/l, P < 0.01), endothelin-1 (0.38 ± 0.11 versus 0.17 ± 0.10 pg/ml, P < 0.001) and fasting insulin (10.4 ± 4.5 versus 5.6 ± 1.6 μU/ml, P < 0.001) with abnormal homeostasis model assessment index of insulin resistance (2.3 ± 1.1 versus 1.2 ± 0.4, P < 0.001). Conclusion Previous heavy alcoholism, in spite of long-term withdrawal, is associated with endothelial dysfunction and a wide cluster of haemodynamic, vascular and metabolic abnormalities that indicate an unfavourable cardiovascular and metabolic risk profile even in apparently disease-free former alcoholics.

Endothelin-A Receptors Mediate Renal Hemodynamic Effects of Exogenous Angiotensin II in Humans

Abstract—To investigate whether endothelin-A receptors mediate hemodynamic changes caused by exogenous Angiotensin II in humans, 7 healthy volunteers on a 250-mmol sodium diet underwent 3 separate p-aminohippurate and inulin-based renal hemodynamic studies. In 2 studies, Angiotensin II (increasing rates of 0.625, 1.25, and 2.5 ng/kg per minute, each for 30 minutes) was infused either alone or combined with endothelin-A blocker, BQ123, 0.4 nmol/kg per minute. A third infusion of BQ123 alone was not followed by any change. Angiotensin II infusion alone produced a progressive decrease in renal blood flow (1080±94 mL/min×1.73 m2 to 801±52, P <0.001, versus baseline) and glomerular filtration rate (115±7 mL/min×1.73 m2 to 97±7, P <0.001) with increase in filtration fraction (0.188±.017 to 0.220±.030, P <0.01). Mean arterial pressure and renal vascular resistance increased markedly (86.8±3.1 to 97.5±4.4 mm Hg, P <0.001 and 83±7 to 133±20 mm Hg/min per liter, P <0.001, respectively). With Angiotensin II+BQ 123, mean arterial pressure still rose (86.2±3.1 to 91.1±4.3, P <0.05 versus both baseline and BQ123 alone) but significantly less than with Angiotensin II alone (P <0.05). Renal blood flow (1077±76 to 993±79, P <0.001) and glomerular filtration rate (115±7 to 105±7, P <0.05) also changed to a significantly lesser extent than with Angiotensin II alone (P <0.05 for both), whereas filtration fraction remained unchanged (0.185±.015 to 0.186±.016). Renal vascular resistance rose only by 17% (82±5 to 95±9, P <0.001 versus baseline as well as versus BQ123 or Angiotensin II alone). The results show that endothelin through Endothelin-A receptors contributes substantially to the systemic and renal vasoconstriction of low-dose exogenous Angiotensin II in healthy humans.

Renal hemodynamics and natriuresis during water immersion in normal humans

The renal vascular and functional responses to acute “central hypervolemia” by water immersion to the neck were determined in six normal subjects. During isotonic-isooncotic expansion by water immersion there was a significant increase in urine flow from 1.1±0.1 to 6.9±1.0 ml/min (p<0.05) and sodium excretion from 99.1±8.8 to 300±28 μEq/min (p<0.05). Glomerular filtration rate did not change while renal blood flow significantly increased during water immersion. Deep intrarenal venous pressure (IRVP) increased from 18.2±1.4 to 32±1.7 mmHg (p<0.05) while mean arterial pressure was unchanged. This marked natriuresis seen during water immersion was associated with reduced renal vascular resistance and increased deep intrarenal venous pressure demonstrating that continued natriuresis could relate to increased capillary hydrostatic pressure.

Calcium and sodium handling during volume expansion in essential hypertension

To evaluate the actual role of extracellular fluid volume (ECFV) expansion per se in modulating the rate of urinary calcium excretion, a thermoneutral water immersion (WI) study was conducted in 10 normal subjects and 30 patients with essential hypertension. Central hypervolemia by 2 hours of WI caused a significant diuretic and natriuretic response (P < .005) in normal subjects; no significant changes were detected in urinary calcium and magnesium excretion. WI provoked either an appropriate or exaggerated natriuresis (P < .001) in 21 hypertensive patients; these subjects also exhibited a highly positive correlation between urinary sodium and calcium excretion during WI (P < .001). In the remaining nine hypertensive patients, WI produced a significant diuretic response, but a barely discernible (P = NS) natriuresis (inappropriate response). These subjects also exhibited a significant reduction of urinary calcium (P < .001) and magnesium (P < .01) excretion. The data indicate that (1) volume expansion per se may have a role in regulating calcium excretion in hypertensive subjects; (2) a calcium leak may be attributable to a close relationship between urinary sodium and calcium metabolism, and causally related to a disturbance of sodium and volume homeostasis in hypertension.

Low-pressure receptor activity and exaggerated natriuresis in essential hypertension.

Urinary sodium excretion, central hemodynamics, and mean arterial pressure (MAP) were studied in 7 normal subjects and 19 hypertensive patients during both central hypervolemia by water immersion to the neck (NI) and extracellular volume expansion by i.v. saline infusion. During 2-hour NI, 12 out of the 19 hypertensives exhibited a significant fall in MAP (p less than 0.001). Exaggerated natriuresis did not occur in these patients (ns). In the remaining 7 hypertensive patients in whom, during NI, MAP was unchanged, exaggerated natriuresis was found (p less than 0.001). During saline infusion, MAP was either unchanged or increased and exaggerated natriuresis was found in all hypertensive patients (p less than 0.001) previously submitted to NI. Our findings suggest that a high MAP is a major determinant of exaggerated natriuresis in arterial hypertension.

Impaired renal haemodynamic response to L-arginine in essential hypertension : role of buffering anion and tubuloglomerular feedback

Objective To investigate whether changes in tubuloglomerular feedback (TGF) dependent upon the tubular effects of buffering anions affect the renal haemodynamic response to L-arginine in healthy (control) individuals and patients with essential hypertension. Methods Mean arterial pressure (MAP), glomerular filtration rate (GFR), renal blood flow (RBF) and fractional excretion of sodium (FENa), chloride (FECl) and lithium (FELi) were measured in 10 control individuals and 10 hypertensive patients during two 3-h infusions of 0.012 mmol/kg per min L-arginine buffered with either HCl or citric acid. Results FELi, FECl and FENa increased (P < 0.001) comparably in controls and hypertensive individuals with arginine–HCl and decreased with arginine–citrate (P < 0.001). MAP was unchanged in controls with arginine–HCl and decreased by 3% with arginine–citrate (P < 0.001), and decreased in hypertensive individuals with both arginine–HCl and arginine–citrate (by 3 and 7%, respectively; P < 0.001). GFR increased with arginine–citrate in controls and hypertensive individuals (by 6.1 and 5.4%, respectively; P < 0.001), but did not change with arginine–HCl in controls and declined by 4.6% in hypertensive individuals (P < 0.05). RBF increased equally after arginine–citrate in controls and hypertensive individuals (by 34 and 33%, respectively; P < 0.001); it also increased after arginine–HCl (22 and 13%, respectively; P < 0.001), but less than after arginine–citrate (P < 0.001), and 41% less in hypertensive individuals than in controls (P < 0.001). Discussion Because arginine–HCl, unlike arginine–citrate, inhibits tubular reabsorption and elicits much less renal vasodilatation than does arginine–citrate, renal haemodynamics in response to L-arginine are modulated by changes in reabsorption and TGF according to the tubular effects of the attendant anion. As renal vasodilatation in hypertensive individuals was reduced only with arginine–HCl, which activates TGF, the blunted vasodilatation of the hypertensive kidney in response to arginine–HCl reflects an exaggerated response to an activated TGF.

Dopamine Blockade Abolishes the Exaggerated Natriuresis of Essential Hypertension

We studied natriuresis during central hypervolaemia by immersing eight normal subjects and eight patients with uncomplicated essential hypertension up to the neck in water, either in the absence (study 1) or presence (study 2) of dopamine blockade by metoclopramide. Water immersion without metoclopramide induced an exaggerated natriuresis in hypertensives compared with normotensives (P less than 0.001). This occurred in the presence of identical hormonal (plasma renin activity, plasma aldosterone and prolactin), renal (creatinine clearance) and pressor responses in both groups (study 1). The marked natriuresis seen during water immersion alone in normotensives was significantly blunted (P less than 0.02) but not abolished during water immersion with addition of metoclopramide. On the other hand, the exaggerated natriuresis found in hypertensives during water immersion alone was completely abolished during water immersion plus dopamine blockade by metoclopramide (study 2). Similar hormonal, renal and pressor changes were detected in both normotensive and hypertensive subjects during water immersion plus metoclopramide administration. Our data demonstrate that metoclopramide abolishes the exaggerated natriuretic response seen in hypertensives during volume expansion produced by water immersion, and suggest that dopamine may play a critical role in mediating the hypernatriuresis of essential hypertension.

Nitric oxide-angiotensin II interactions and renal hemodynamic function in patients with uncomplicated type 1 diabetes

The objective is to elucidate the effect of nitric oxide (NO)-renin-angiotensin system (RAS) interactions on renal hemodynamic function in uncomplicated, type 1 diabetes mellitus (DM). In 14 salt-replete, male healthy volunteers (C) and 9 male DM patients on euglycemia, glomerular filtration rate (GFR), renal blood flow (RBF), filtration fraction (FF), and sodium excretion (UNaV) were measured at baseline and during a 90-min infusion of 3.0 μg·kg⁻¹·min⁻¹ NG-nitro-L-arginine-methyl-ester (L-NAME) after 3 days of pretreatment with either placebo (PL) or 50 mg losartan (LOS). Baseline GFR, RBF, and FF were higher in DM (P < 0.005). In the C group, PL + L-NAME caused declines in GFR (101 ± 3 to 90 ± 3 ml·min⁻¹·1.73 m⁻²), RBF (931 ± 22 to 754 ± 31 ml·min⁻¹·1.73 m⁻²), and UNaV (158 ± 12 to 82 ± 18 μmol/min) and an increase in FF (0.19 ± 0.02 to 0.21 ± 02; P < 0.001), which were not influenced by LOS pretreatment (P > 0.05 for LOS + L-NAME-C vs. PL + l-NAME-C). In DM, PL + L-NAME resulted in exaggerated renal effects, with changes in GFR (128 ± 3 to 104 ± 3 ml·min⁻¹·1.73 m⁻²), RBF (1,019 ± 27 to 699 ± 34 ml·min⁻¹·1.73 m⁻²), UNaV (150 ± 13 to 39 ± 14 μmol/min), and FF (0.22 ± 0.03 to 0.26 ± 0.02) that were significantly greater vs. PL + L-NAME-C (P < 0.005). LOS pretreatment blunted GFR, RBF, FF, and UNaV responses to L-NAME in DM (P < 0.005 vs. PL + L-NAME-DM), resulting in a response profile that was similar to PL + L-NAME and LOS + L-NAME in C (P > 0.05). Renal responses to L-NAME in uncomplicated, type 1 DM are exaggerated vs. C, consistent with an upregulation of NO bioactivity. LOS, without effects in C, prevents the accentuated actions of L-NAME in DM, thus indicating an augmented role for NO-RAS interactions in renal hemodynamic function in DM.