A comparison of reactive oxygen species metabolism in the rat aorta and vena cava: focus on xanthine oxidase

Reactive oxygen species (ROS) are important mediators in vascular biology. Venous function, although relevant to cardiovascular disease, is still understudied. We compared aspects of ROS metabolism between a major artery (the aorta) and a major vein (the vena cava, VC) of the rat, with the hypothesis that venous ROS metabolism would be overall increased compared with its arterial counterpart. Superoxide and hydrogen peroxide (H2O2) release in basal conditions was higher in VC compared with aorta. The antioxidant capacity for H2O2 was also higher in VC than in aorta. Exogenous superoxide induced a higher contraction in VC compared with aorta. Protein expression of three major ROS metabolizing enzymes, xanthine oxidase (XO), CuZn-SOD, and catalase, was higher in VC compared with aorta. Because XO seemed a likely source of the higher VC ROS levels, we examined it further and found higher mRNA expression and activity of XO in VC compared with aorta. We also investigated the impact of XO inhibition by allopurinol on aorta and VC functional responses to norepinephrine, ANG II, ET-1, and ACh. Maximal ET-1-mediated contraction was decreased by allopurinol in VC but not in the aorta. Our results suggest that there are overall differences in ROS metabolism between aorta and VC, with the latter operating normally at a higher set point, releasing but also being able to handle, higher ROS levels. We propose XO to be an important source for these differences. The result of this particular comparison may be reflective of a general arteriovenous contrast.     

Technical Aspects of the Mouse Aortocaval Fistula

Technical aspects of creating an arteriovenous fistula in the mouse are discussed. Under general anesthesia, an abdominal incision is made, and the aorta and inferior vena cava (IVC) are exposed. The proximal infrarenal aorta and the distal aorta are dissected for clamp placement and needle puncture, respectively. Special attention is paid to avoid dissection between the aorta and the IVC. After clamping the aorta, a 25 G needle is used to puncture both walls of the aorta into the IVC. The surrounding connective tissue is used for hemostatic compression. Successful creation of the AVF will show pulsatile arterial blood flow in the IVC. Further confirmation of successful AVF can be achieved by post-operative Doppler ultrasound.     

Localization of lipids in the aortic wall with imaging TOF-SIMS

Time-of-flight secondary-ion-mass-spectrometry (TOF-SIMS) was utilized to address the issue of localization of lipids and inorganic ions in healthy rat aorta and human atherosclerotic plaque. Pieces of rat aorta were high pressure frozen, freeze-fractured and freeze dried. The samples were analyzed by imaging TOF-SIMS equipped with a Bi(1-7)(+)-source. Reference lipid samples were analyzed and compared to data obtained by analysis of the rat aorta samples. Fatty acids, cholesterol, oxysterol and diacylglycerols were detected and localized. A heterogeneous lipid distribution could be shown in the aorta, where the lamellae of the aorta, distinguished by imaging of CN(-), appeared enriched in cholesterol, oxysterol and diacylglycerols, while the smooth muscle tissue, identified by imaging of PO(3), appeared enriched in phosphocholine. Palmitic/palmitoleic acid and stearic/oleic acid appeared to be heterogeneously distributed over the aorta with high concentration areas located especially in the tunica media region of the aorta. Human atherosclerotic plaque showed an irregular cholesterol distribution mainly located in spots in the intima region with elongated diacylglycerol regions located mainly in the media region.     

Isolation and Excision of Murine Aorta; A Versatile Technique in the Study of Cardiovascular Disease

Cardiovascular disease is a broad term describing disease of the heart and/or blood vessels. The main blood vessel supplying the body with oxygenated blood is the aorta. The aorta may become affected in diseases such as atherosclerosis and aneurysm. Researchers investigating these diseases would benefit from direct observation of the aorta to characterize disease progression as well as to evaluate efficacy of potential therapeutics. The goal of this protocol is to describe proper isolation and excision of the aorta to aid investigators researching cardiovascular disease. Isolation and excision of the aorta allows investigators to look at gross morphometric changes as wells as allowing them to preserve and stain the tissue to look at histologic changes if desired. The aorta may be used for molecular studies to evaluate protein and gene expression to discover targets of interest and mechanisms of action. This technique is superior to imaging modalities as they have inherent limitations in technology and cost. Additionally, primary isolated cells from a freshly isolated and excised aorta can allowing researchers to perform further in situ and in vitro assays. The isolation and excision of the aorta has the limitation of having to sacrifice the animal however, in this case the benefits outweigh the harm as it is the most versatile technique in the study of aortic disease.     

Rheological properties of the thoracic aorta in normal and WHHL rabbits

The tension-strain, stress-strain and stress relaxation curves of longitudinal and circumferential strips of proximal thoracic aortas in normal and WHHL rabbits of different ages were determined using a tensile testing instrument. Wall distensibility of longitudinal and circumferential strips was the greatest in the normal aorta and decreased with advancing age in the atherosclerotic aorta. The wall thickness of the atherosclerotic aorta was positively related to age with a correlation coefficient of 0.66(p less than 0.01). The incremental elastic moduli calculated from the stress-strain curves increased with advancing age in the atherosclerotic aorta. Accordingly, the decreased distensibility of the atherosclerotic wall may be due to the increased wall thickness caused by the intimal thickening as well as to the increase in wall stiffness caused by the increased elastic modulus. The viscoelasticity of the atherosclerotic aorta was larger than that of the normal aorta. This reflects the mechanical effect of atherosclerotic changes that occurred in the thickened intima.     

Pulsatile flow visualization in the abdominal aorta under differing physiologic conditions: implications for increased susceptibility to atherosclerosis.

The infrarenal abdominal aorta is a common site for clinically significant atherosclerosis. As has been shown in other susceptible locations, vessel geometry, flow division rates, and pulsatility may result in hemodynamic conditions which influence the preferential localization of disease in the abdominal aorta segment. Pulsatile flow visualization was performed in a glass model of the aorta constructed from measurements of angiograms and cadaver aortas. Flow rates and pulsatile waveforms were varied to reflect typical physiological conditions. Under normal resting conditions, the flow patterns in the infrarenal aorta were more complex than those in the suprarenal location. Time varying vortex patterns appeared at the level of the renal arteries and propagated through the infrarenal aorta into the common iliac arteries. A region of oscillating velocity direction extended from the renal arteries to the aortic bifurcation along the posterior wall. Dye became trapped along the posterior wall, requiring several cardiac cycles for clearance. In contrast, there was rapid clearance of the dye in the anterior aorta. Under postprandial conditions, the flow patterns in the aorta were basically unchanged. Simulated exercise conditions created laminar hemodynamic features very different from the resting conditions, including a decrease in dye residence time. This study reveals significant time-dependent variations in the hemodynamics of the abdominal aorta under differing physiologic conditions. Hemodynamic factors such as low wall shear stress, oscillating shear direction, and high particle residence time may be related to the clinically seen preferential plaque localization in the infrarenal aorta.     

Methylation of phospholipids in microsomes of the rat aorta

The methylation of phospholipids by S-adenosyl-L-methionine was characterized in microsomes prepared from strips of rat aorta. In the presence of 0.5 microM S-adenosyl-L-methionine, endogenous phosphatidylethanolamine was methylated to form three products: phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine and phosphatidylcholine. In the presence of 150 microM S-adenosyl-L-methionine the methylation activity increased more than 50-fold and the principal radioactive product was phosphatidylcholine. Optimal activity was at pH 9 and no magnesium requirement was detected. Exogenous phosphatidylethanolamine, phosphatidyl-N-monomethylethanolamine and phosphatidyl-N,N-dimethylethanolamine served as substrates for the enzyme. The methylation of exogenous phosphatidyl-N,N-dimethylethanolamine proceeded at a slower rate. Incubation of trypsin with the aorta microsomes reduced the enzymatic activity and reduced the relative yield of phosphatidyl-N-monomethylethanolamine. Phospholipase C degraded the methylated phospholipids, but phosphatidyl-N,N-dimethylethanolamine appeared to be less accessible to the phospholipase. The phospholipid methylation activity was inhibited by the addition of S-adenosyl-L-homocysteine or by L-homocysteinethiolactone. When intact strips of rat aorta were incubated with L-[methyl-3H]methionine, [3H]methyl groups were incorporated into phospholipids. This incorporation was inhibited when L-homocysteinethiolactone was added to the incubation. Polarized fluorescence of diphenylhexatriene in aorta microsomes was measured to determine the apparent membrane fluidity. When intact strips of aorta were incubated with methionine or with L-homocysteinethiolactone, methionine enhanced and L-homocysteinethiolactone decreased apparent fluidity of the microsomal membranes. Phospholipid methylation activity was examined in aorta microsomes prepared from genetically spontaneous hypertensive SHR strain rats. Phospholipid methylation activity was substantially greater in the SHR aorta microsomes than in microsomes prepared from Wistar-Kyoto WKY control strain aorta. Membrane fluidity was greater in the SHR aorta microsomes than in the WKY aorta microsomes. The hypothesis that phospholipid methylation activity influences fluidity of membranes and the possible involvement of methylated phospholipids in aorta membrane functions are discussed.     

Kinetic differences between Ca(2+)-dependent K+ channels in smooth muscle cells isolated from normal and atherosclerotic human aorta.

The properties of large conductance Ca(2+)-dependent K+ channels in smooth muscle cells (SMC) isolated from normal and atherosclerotic human aorta were studied using the patch-clamp technique. It was shown that SMC from normal human aorta possess a homogeneous population of normal Ca(2+)-dependent K+ channels. In atherosclerotic aorta two kinetically different types of these channels could be distinguished: along with normal 'long' (L)-type channels there appeared channels of 'short' (s)-type. Under similar conditions s-type channels had about a four times shorter mean open time. About five times higher [Ca2+]in was necessary for s-type channels to reach the probability of the channels being open equal to L-type channels. No differences in conductance and voltage dependency were found between the two channel types. Channels of the s-type resembled those previously described in SMC isolated from foetal human aorta. Thus, it can be suggested that during the development of atherosclerosis a population of SMC with s-type Ca(2+)-dependent K+ channels appears in human aorta.     

Investigation of hemodynamics in the development of dissecting aneurysm within patient-specific dissecting aneurismal aortas using computational fluid dynamics (CFD) simulations

Aortic dissecting aneurysm is one of the most catastrophic cardiovascular emergencies that carries high mortality. It was pointed out from clinical observations that the aneurysm development is likely to be related to the hemodynamics condition of the dissected aorta. In order to gain more insight on the formation and progression of dissecting aneurysm, hemodynamic parameters including flow pattern, velocity distribution, aortic wall pressure and shear stress, which are difficult to measure in vivo, are evaluated using numerical simulations. Pulsatile blood flow in patient-specific dissecting aneurismal aortas before and after the formation of lumenal aneurysm (pre-aneurysm and post-aneurysm) is investigated by computational fluid dynamics (CFD) simulations. Realistic time-dependent boundary conditions are prescribed at various arteries of the complete aorta models. This study suggests the helical development of false lumen around true lumen may be related to the helical nature of hemodynamic flow in aorta. Narrowing of the aorta is responsible for the massive recirculation in the poststenosis region in the lumenal aneurysm development. High pressure difference of 0.21 kPa between true and false lumens in the pre-aneurismal aorta infers the possible lumenal aneurysm site in the descending aorta. It is also found that relatively high time-averaged wall shear stress (in the range of 4-8 kPa) may be associated with tear initiation and propagation. CFD modeling assists in medical planning by providing blood flow patterns, wall pressure and wall shear stress. This helps to understand various phenomena in the development of dissecting aneurysm.     

Attenuation of lipid peroxidation and hyperlipidemia by quercetin glucoside in the aorta of high cholesterol-fed rabbit

Antioxidative activity of dietary flavonoids is suggested to be, at least partly, responsible for a wide variety of their biological effects relating to anti-atherosclerosis. However, it is not known whether dietary flavonoids reach to the target site and act as antioxidants. In this study, we tried to evaluate the antioxidative effect of quercetin 3-O-beta-D-glucoside (Q3G), a typical flavonoid present in vegetables, in rabbit aorta. New Zealand White rabbits were fed a control diet (control group), 2.0% cholesterol diet (HC group) and 2.0% cholesterol plus 0.1% Q3G (HC + Q3G group) for one month. The amounts of total cholesterol, triacylglycerol and total fatty acids in both the plasma and aorta were significantly lower in the HC + Q3G group as compared with the HC group. Quercetin was detected in the aorta of the HC + Q3G group after enzymatic deconjugation, indicating that quercetin accumulated as conjugated metabolites in the aorta. The contents of TBA-reacting substances (TBARS) and cholesteryl ester hydroperoxides (CEOOH) in the aorta of the HC + Q3G group were significantly lower than those in the HC group. The aorta of HC + Q3G group was more resistant than that of HC group in copper ion-induced lipid peroxidation ex vivo. HC + Q3G group accumulated a higher amount of vitamin E per total cholesterol than HC group in the aorta. These results strongly suggest that quercetin glucosides accumulate in the aorta as their metabolites and attenuate lipid peroxidation occurring in the aorta, along with the attenuation of hyperlipidemia.     

Inhibitors of in vitro mineralization from rabbit aorta and their role in biomineralization

Mineralization of aorta is known to occur late in life and appears to be a pathological phenomenon. In vitro studies revealed that the matrix prepared from the thoracic aorta pieces after their extraction with 3% Na₂HPO₄ and 0.1 mM CaCl₂ were mineralized under physiological conditions of temperature, pH, and ionic strength of the media to form matrix-bound mineral phase resembling hydroxyapatite in nature. However, the matrix identically prepared from the unextracted rabbits aortae failed to mineralize under identical assay conditions. The addition of the aorta extract in the assay system inhibited the above mineralization process. Standard biochemical techniques, e.g., dialysis, ion exchange, and molecular sieve chromatography, sodium dodecyl sulfate–polyacrylamide gel electrophoresis, and amino acid analysis by high-performance liquid chromatography were employed to isolate, purify, and characterize the potent inhibitory biomolecules from the aorta extract. The inhibitory activity of the aorta extract was found to be primarily due to the presence of three biomolecules having molecular weights of 66, 45, and 27–29 kDa. The above inhibitory biomolecules loosely associated with aorta may be involved in the control of calcification associated with arteriosclerosis. J. Cell. Biochem. 68:287–297, 1998. © 1998 Wiley-Liss, Inc.     

Effect of phorbol ester on contractile response of aorta from endotoxic rats

The influence of phorbol ester on the isometric contractile response of aorta from endotoxic rats was examined. In endotoxic rat aorta, the contractile responses to KCl and phorbol 12,13-dibutyrate (PDBu) were both remarkably diminished, compared to those in control rat aorta. Preincubation with PDBu augmented the aortic contractile response to KCl in both control and endotoxic rats. This augmentative effect of PDBu was significantly more pronounced in endotoxic rats than in controls. When the contractile response to 80 mM KCl reached a plateau after PDBu pretreatment, addition of 5 mM CaCl2 (final concentration) to the organ bath completely reversed the diminished contractile response of endotoxic rat aorta to the control level. These results suggest that the hyporesponsiveness of endotoxic rat aorta to KCl may be caused by decreases in both protein kinase C mediated response and calcium sensitivity of vascular smooth muscle cells.     

Purification and characterization of bovine aorta ribonucleases

1. Two ribonucleases (aorta ribonuclease I and aorta ribonuclease II) from bovine aorta were purified 4611-fold and 667-fold respectively. Ethanolic precipitation, acid extraction, isoionic precipitation at pH3.5 and Bio-Rex 70 column chromatography were the methods employed. 2. Aorta ribonuclease I exhibited no deoxyribonuclease or alkaline phosphatase activity. 3. Aorta ribonuclease I appeared to be homogeneous when subjected to discontinuous gel electrophoresis. 4. Aorta ribonuclease II exhibited the same properties as aorta ribonuclease previously isolated. 5. The activities of the aorta ribonucleases and pancreatic ribonuclease on homopolymers and dinucleoside phosphates were compared. 6. Aorta ribonuclease I exhibited optimum pH7.5 and, under the assay conditions used, optimum temperature 60 degrees .     

Differences in inositol phosphate production in rat tail artery and thoracic aorta

Pharmacomechanical coupling of vascular smooth muscle is believed to be mediated by inositol trisphosphate (IP3). Numerous studies have demonstrated an increase in inositol phosphates following tissue stimulation using either intact aortic strips or cultured cells from aorta. However, little information is available concerning inositol phosphates in vascular tissue other than in the large conduit vessel, the aorta. This present study was designed to examine the role of inositol phosphate metabolism following adrenergic stimulation of the muscular rat tail artery as compared to the aorta. Segments of thoracic aorta and tail artery from male Sprague Dawley rats were labeled with [3H]inositol and stimulated with norepinephrine. The norepinephrine concentration that resulted in a half-maximal stimulation of inositol phosphates was approximately 10(-6) M in both the aorta and tail artery. Although the sensitivity of the two vessels to norepinephrine stimulation were similar, the stimulated levels of IP, IP2, and IP3 were from 1 to 2 orders of magnitude greater in the tail artery than in aorta. IP production in aorta and tail artery was a linear function of time (from 0 to 30 min). Significant levels of IP3 (the 1,4,5-IP3 isomer as determined by HPLC) could only be detected in the tail artery and appeared to be produced optimally after 5 min of stimulation. The several order of magnitude increase in adrenergic stimulated inositol phosphate production in the tail artery was not due to either an increased magnitude of [3H]inositol incorporated into PI, PIP, and PIP2 or to a greater percentage of smooth muscle cells per unit tissue of the rat tail artery. We believe the results of this study demonstrate that the increased inositol phosphate metabolism in the vascular smooth muscle cells of the tail artery is an intrinsic property of the cell. Moreover, due to the significant levels of all inositol phosphates produced in the tail artery, this muscular artery may be a better model, as compared to the aorta, for future studies investigating pharmacomechanical coupling of vascular smooth muscle.     

A study of aneurysmal lesions of the aorta using magnetic resonance tomography

Altogether 23 patients with aneurysmal aortic lesions of various sites were investigated using MR-tomography. Sagittal and axial projections were used for visualization of the thoracic aorta, frontal and axial ones--for visualization of the abdominal aorta. As compared to radionuclide and x-ray methods of investigation, MR-tomography was characterized by a high informative value in the detection of aneurysmal lesions. Despite a limited number of patients the authors managed to diagnose aortic stratification which could be well visualized in the abdominal aorta.     

Some characteristics of intimal folds in the rabbit aorta

A stereomicroscopic study of fresh rabbit aorta has shown that the intimal folds form a special pattern which reappears when the aorta is relaxed after stretching. The pattern of intimal folds seems to be adapted to and may be the result of continuously repeated movements of the vessel wall. This supports the view hat intimal folds are present in vivo.     

Passive viscoelastic properties of the rabbit aorta in vitro

Tensile tests on longitudinal and circumferential strips of the rabbit aorta have been performed. Stress-strain and relaxation parameters have been estimated with respect to four stress levels and three positions on the aorta. Stress-strain data indicate that in longitudinal direction the aorta becomes more compliant with distance from the aortic arch. The opposite tendency is found for the circumferential direction. Stress-relaxation is found to be strongly dependent on the stress level. The results are discussed with regard to arterial dynamics.     

Measuring,reversing, and modeling the mechanical changes due to the absence of Fibulin-4 in mouse arteries

Mice with a smooth muscle cell (SMC)-specific deletion of Fibulin-4 (SMKO) show decreased expression of SMC contractile genes, decreased circumferential compliance, and develop aneurysms in the ascending aorta. Neonatal administration of drugs that inhibit the angiotensin II pathway encourages the expression of contractile genes and prevents aneurysm development, but does not increase compliance in SMKO aorta. We hypothesized that multidimensional mechanical changes in the aorta and/or other elastic arteries may contribute to aneurysm pathophysiology. We found that the SMKO ascending aorta and carotid artery showed mechanical changes in the axial direction. These changes were not reversed by angiotensin II inhibitors, hence reversing the axial changes is not required for aneurysm prevention. Mechanical changes in the circumferential direction were specific to the ascending aorta; therefore, mechanical changes in the carotid do not contribute to aortic aneurysm development. We also hypothesized that a published model of postnatal aortic growth and remodeling could be used to investigate mechanisms behind the changes in SMKO aorta and aneurysm development over time. Dimensions and mechanical behavior of adult SMKO aorta were reproduced by the model after modifying the initial component material constants and the aortic dilation with each postnatal time step. The model links biological observations to specific mechanical responses in aneurysm development and treatment.     

Sutureless aortic valve with supracoronary ascending aortic replacement as an alternative strategy for composite graft replacement in elderly patients

Netherlands Heart Journal - Aortic valve disease is frequently associated with ascending aorta dilatation and can be treated either by separate replacement of the aortic valve and ascending aorta...