Measurement of endothelium-dependent vasodilation in mice--brief report (original) (raw)
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In vivo measurement of flow-mediated vasodilation in living rats using high-resolution ultrasound
AJP: Heart and Circulatory Physiology, 2008
In humans, endothelial vasodilator function serves as a surrogate marker for cardiovascular health and is measured as changes in conduit artery diameter after temporary ischemia (flow-mediated dilation; FMD). Here, we present an FMD-related approach to study femoral artery (FA) vasodilation in anesthetized rats. Diameter and Doppler-flow were monitored in the FA. Using high-resolution ultrasound (35 MHz) and automated analysis software, we detected dose-dependent vasodilation using established endothelium-independent (IV nitroglycerin EC 50 =3.3x10 -6 mol/L, peak 21 % (SD 4)) and endothelium-dependent (IA acetylcholine EC 50 =1.3x10 -6 mol/L, peak 27 % (SD 4)) pharmacologic vasodilators. Wall shear stress (WSS) induced by intra-aortic injection of adenosine and infusion of saline at increasing rates (1.5-4.5 mL/min) led to vasodilation at 1-2 min. Transient hindlimb ischemia by common iliac occlusion (5 min) led to reactive hyperemia with flow-velocity and WSS increase and was followed by FA dilation (16 % (SD 2)), the latter of which was completely abolished by NO-synthase (NOS) inhibition with L-NMMA (1 % (SD 2)). FMD was significantly reduced in adult 20-24 week old animals as compared to 9-10 week old animals, consistent with agedependent endothelial dysfunction (16 % (SD 3) vs 10 % (SD 3), p<0.05). While FMD was completely NOS-dependent in 9-10 week old animals, NOS-dependent mechanisms accounted for only half of the FMD in 20-24 week old animals, with the remainder being blocked by charybdotoxin and apamin, suggesting contribution of endothelium-derivedhyperpolarizing-factor. To our knowledge, this is the first integrative physiologic model to reproducibly study FMD of conduit arteries in living rats.
Assessment of mouse hind limb endothelial function by measuring femoral artery blood flow responses
Journal of Vascular Surgery, 2011
Objective: Substantial progress has been made in cell therapy strategies and in gene-and cytokine-introduced angiogenesis using a variety of mouse models, such as hind limb ischemia models. Endothelial function is an important target in evaluating the effects and outcomes of these potential therapies. Although animal models have been established for estimating endothelium-dependent function by measuring the blood flow responses in carotid and renal arteries and the abdominal aorta, a model specific for an indicated hind limb by measuring femoral artery blood flow (FABF) has not yet been established. Methods: A 2-day protocol was designed, including exploration of the segmental femoral artery on the first day, and evaluation of endothelium-dependent vasodilatation function the next day. By placing a transonic flow probe around the left femoral artery, the FABF in response to endothelium-dependent and endothelium-independent vasodilatory stimulations was reproducibly measured. Hemodynamic measurements, including the left FABF and mean arterial pressure, were recorded. Results: In normal controls, the baseline left FABF averaged 0.12 ؎ 0.01 mL/min. Acetylcholine increased the FABF up to 0.41 ؎ 0.02 mL/min. Rose bengal-associated photochemical injury was titrated to cause endothelial dysfunction but without disturbing the integrity of the endothelial layer. The response to acetylcholine significantly decreased 10 minutes after photochemical injury and was further impaired after 1 and 24 hours. However, the response to nitroprusside was preserved. A femoral and iliac artery wire-injury model was also introduced to cause endothelial and smooth muscle cell injury. One day after the wire injury, the responses to acetylcholine and nitroprusside injections were both remarkably attenuated.
Role of Endothelial Nitric Oxide in Shear Stress–Induced Vasodilation of Human Microvasculature
Circulation, 2001
Background —It has been proposed that flow-mediated shear stress regulates vascular tone; however, whether this operates in the human microcirculation is unknown. This study was designed to investigate the effect of shear stress on human microvascular tone, to assess the contribution of nitric oxide (NO), and to determine whether this mechanism is defective in hypertension and in hypercholesterolemia. Methods and Results —In 9 normal controls (NC), 11 hypertensive patients (HT), and 12 hypercholesterolemic patients (HChol), arteries (internal diameter 201±26 μm) isolated from gluteal fat biopsies were cannulated and perfused in chambers. Shear stress was induced by increasing the flow rate from 1 to 50 μL/min after preconstriction with norepinephrine (NE). Arterial internal diameter was expressed as percent of NE-induced constriction. In NC, shear stress induced flow-dependent vasodilation from 23±9% at 1 μL/min to 53±14% at 50 μL/min ( P <0.0001), which was abolished by endothel...
Flow-Mediated Vasodilation as a Diagnostic Modality for Vascular Failure
Hypertension Research, 2008
Vascular endothelial dysfunction represents an initial step of "vascular failure," which we have recently proposed as a comprehensive syndrome of failed vascular functions that extends from risk factors to established atherosclerotic disease. The early detection of vascular failure is essential in order to appropriately intervene and prevent its progression. Many efforts have been made to assess vascular endothelial function, and one of the most promising methods is the measurement of endothelium-dependent flow-mediated vasodilation (FMD) using high-frequency ultrasonographic imaging and transient occlusion of the brachial artery. The reactive hyperemia caused by the transient brachial arterial occlusion induces the release of local nitric oxide, resulting in vasodilation that can be quantified as an index of vasomotor function. The noninvasive nature of this technique allows repeated measurements over time to study the effectiveness of various interventions that may affect vascular health. Although there are technical and interpretive limitations of this technique, FMD-guided therapeutic approaches for vascular failure should contribute to the improvement of cardiovascular mortality and morbidity. (Hypertens Res 2008; 31: 2105-2113)
Novel aspects of endothelium-dependent regulation of vascular tone
Kidney International, 2006
The vascular endothelium plays a crucial role in the regulation of vascular homeostasis and in preventing the initiation and progress of cardiovascular disease by controlling mechanical functions of the underlying vascular smooth muscle. Three vasodilators: nitric oxide (NO), prostacyclin, and endothelium-derived hyperpolarizing factor, produced by the endothelium, underlie this activity. These substances act in a co-ordinated interactive manner to maintain normal endothelial function and operate as support mechanisms when one pathway malfunctions. In this review, we discuss recent advances in our understanding of how gender influences the interaction of these factors resulting in the vascular protective effects seen in pre-menopausal women. We also discuss how endothelial NO synthase (NOS) can act in both a pro-and anti-inflammatory action and therefore is likely to be pivotal in the initiation and time course of an inflammatory response, particularly with respect to inflammatory cardiovascular disorders. Finally, we review recent evidence demonstrating that it is not solely NOS-derived NO that mediates many of the beneficial effects of the endothelium, in particular, nitrite acts as a store of NO released during pathological episodes associated with NOS inactivity (ischemia/hypoxia). Each of these more recent findings has emphasized new pathways involved in endothelial biology, and following further research and understanding of the significance and mechanisms of these systems, it is likely that new and improved treatments for cardiovascular disease will result.
Journal of Cardiac Failure, 1999
After myocardial infarction (MI), nitric oxide (NO)-mediated vasorelaxation is attenuated in both conduit and resistance arteries. To determine if the attenuated vasorelaxation after MI is due to downregulation of eNOS protein, pharmacological, immunoblotting, and gene transfer of eNOS were performed in rats 3 weeks after MI. Gene transfer was accomplished using a "first-generation" serotype 5, replication-deficient, adenoviral vector (1.2×10 9 pfus) containing eNOS cDNA in the hindlimb vasculature for 30 min. Five days after infection, overexpression of eNOS protein was confirmed by immunohistochemical staining and immunoblotting. Recombinant gene expression was localized primarily to the vascular endothelial cells. After MI, eNOS protein level decreased (3.3±0.9 vs 2.1±0.8 intensity units/ g protein, n=6, P<0.05); after gene transfer it increased (P<0.05) twofold to 4.3±1.2 intensity units/ g protein, n=5. There were no changes in hemodynamics in MI rats transfected with eNOS. Acetylcholine (ACh)-stimulated vasorelaxation was decreased (P<0.05) by 30% after MI and was restored to normal with eNOS transfection. Addition of 100 N G-nitro-arginine methyl ester (-NAME) abolished the difference between sham, MI, and MI transfected rats. -arginine (1 m) restored the ACh-response in MI-transfected rats toward control, but it did not eliminate the difference between MI and sham rats. We conclude that the attenuated endothelial NO-mediated vasorelaxation in the hindlimb after MI is due to a downregulation of eNOS protein and overexpression of eNOS transgene restores normal endothelial NO-mediated vasorelaxation.
Arteriosclerosis, Thrombosis, and Vascular Biology, 2007
Objective-Arteriogenesis is the major mechanism of vascular growth, which is able to compensate for blood flow deficiency after arterial occlusion. Endothelial nitric oxide synthase (eNOS) activity is essential for neovascularization, however its specific role in arteriogenesis remains unclear. We studied the role of eNOS in arteriogenesis using 3 mouse strains with different eNOS expression. Methods and Results-Distal femoral artery ligation was performed in eNOS-overexpressing mice (eNOStg), eNOSdeficient (eNOS Ϫ/Ϫ ) mice, and wild type (WT) controls. Tissue perfusion and collateral-dependent blood flow were significantly increased in eNOStg mice compared with WT only immediately after ligation. In eNOS Ϫ/Ϫ mice, although tissue perfusion remained significantly decreased, collateral-dependent blood flow was only decreased until day 7, suggesting normal, perhaps delayed collateral growth. Histology confirmed no differences in collateral arteries of eNOStg, eNOS Ϫ/Ϫ , and WT mice at 1 and 3 weeks. Administration of an NO donor induced vasodilation in collateral arteries of eNOS Ϫ/Ϫ mice, but not in WT, identifying the inability to vasodilate collateral arteries as main cause of impaired blood flow recovery in eNOS Ϫ/Ϫ mice. Conclusions-This study demonstrates that eNOS activity is crucial for NO-mediated vasodilation of peripheral collateral vessels after arterial occlusion but not for collateral artery growth. (Arterioscler Thromb Vasc Biol.
Absence of Flow-Mediated Vasodilation in the Rabbit Femoral Artery
Physiological Research, 2010
The purpose of this study was to determine if there is flowmediated vasodilation of the femoral artery in response to progressive increases in flow within a physiological range observed in the in vivo experiments. Femoral artery blood flow was determined in conscious rabbits (n=5) using chronically implanted flowprobes. Resting blood flow was 8.3±0.6 ml/min and increased to 39.9±5.4 ml/min during high intensity exercise. Femoral arteries (n=12, 1705±43 µm outer diameter) harvested from a separate group of rabbits were mounted on cannulas and diameter was continuously monitored by video system. Functional integrity of the endothelium was tested with acetylcholine. The arteries were set at a transmural pressure of 100 mm Hg and preconstricted with phenylephrine to 73±3 % of initial diameter. Using a roller pump with pressure held constant, the arteries were perfused intraluminally with warmed, oxygenated Krebs' solution (pH=7.4) over a physiological range of flows up to 35 ml/min....
Nitric Oxide, 2015
Blood vessels are continuously exposed to various stresses such as mechanical strains and neurosignals. Besides its role as a barrier between blood and other tissues, the endothelium is a highly important cell layer for the regulation of vascular tone. Indeed, depending on the signal perceived by endothelial cells, it can drive a vasoconstrictor or vasodilator signal. This review presents mechano-receptors and neuroreceptors (restricted to neuropeptides) leading to vessel relaxation via the production of nitric oxide. Finally, some pieces of evidence of a potential cross-talk between these two kinds of stimuli are discussed.
American Journal of Physiology-Heart and Circulatory Physiology, 2007
We determined the contributions of various endothelium-derived relaxing factors to control of basal vascular tone and endothelium-dependent vasodilation in the mouse hindlimb in vivo. Under anesthesia, catheters were placed in a carotid artery, jugular vein, and femoral artery (for local hindlimb circulation injections). Hindlimb blood flow (HBF) was measured by transit-time ultrasound flowmetry. Nω-nitro-l-arginine methyl ester (l-NAME, 50 mg/kg plus 10 mg·kg−1·h−1), to block nitric oxide (NO) production, altered basal hemodynamics, increasing mean arterial pressure (30 ± 3%) and reducing HBF (−30 ± 12%). Basal hemodynamics were not significantly altered by indomethacin (10 mg·kg−1·h−1), charybdotoxin (ChTx, 3 × 10−8 mol/l), apamin (2.5 × 10−7 mol/l), or ChTx plus apamin (to block endothelium-derived hyperpolarizing factor; EDHF). Hyperemic responses to local injection of acetylcholine (2.4 μg/kg) were reproducible in vehicle-treated mice and were not significantly attenuated by l-...