Rabbit Abdominal Aorta Research Articles

Abstract 334: An Echogenic Clot Method for Thrombolysis Monitoring of Directed Lytics in Thrombotic Stroke

Background: We have previously demonstrated thrombolytic efficacy of tissue plasminogen activator (tPA)-loaded echogenic liposomes (TELIP), a directed therapeutic construct that features exposed tPA fibrin-binding sites, in a rabbit abdominal aorta thrombosis model. The most relevant animal model for evaluation of directed thrombolytic therapy for ischemic stroke is the rabbit thrombotic stroke model previously used to validate recombinant tPA (rtPA; Alteplase). The ability to precisely monitor tPA-mediated thrombus dissolution in vivo is important for quantitative assessment of directed TELIP efficacy. Hypothesis: A gas-free ultrasound contrast agent can be incorporated into blood clots at a concentration that does not affect the tPA-mediated clot dissolution rate, while enabling quantitative assessment of the clot dissolution rate. Methods: In 1.5-ml Eppendorf tubes, 0.2-ml clots were formed from a mixture of whole rabbit blood, 1 M calcium chloride, human thrombin and various amounts of microcrystalline cellulose. At 0-time, 50 μg rtPA in 0.5 ml porcine plasma was added to each tube. Washed clots in tubes were weighed with an analytical balance at 30, 60 and 90 minutes. Clot echogenicity at each time point was assessed with a Philips HDI 5000 ultrasound system using an L12-5 linear array probe positioned laterally to tubes placed in an anechoic chamber. Recorded Images were subjected to videodensitometric analysis that converted image reflectivity to mean gray scale values (MGSV). Results: We found that 1.12 mg/ml of microcrystalline cellulose in rabbit blood clots (0.2 ml) provided optimal echogenicity without affecting the clot dissolution rates (0.3-0.6 mg/min.) caused by 100 μg/ml of rtPA. The clot dissolution rate measured by videodensitometric analysis of serial sonograms of the echogenic clots agreed well with that determined by mass loss measurements (0.28% 0-time value/minute). Conclusions: We have developed a method for monitoring rtPA-mediated clot mass loss by ultrasound imaging techniques and validated it in vitro. This method will be important for demonstrating the enhanced efficacy and decreased hemorrhagic effects provided by directed tPA vehicles relative to systemic administration of the free thrombolytic.

Design and characterization of a novel biocorrodible iron-based drug-eluting coronary scaffold

Long corrosion period and slow resorption in vivo remain major limitations for iron-based bioresorbable scaffolds. This work focused on the design and characterization of a novel iron-based drug-eluting coronary scaffold (IBS scaffold) made of nitrided iron materials. The 53μm IBS scaffold shows good device performance comparable to a current mainstream drug-eluting coronary stent (Xience Prime™) due to the good comprehensive mechanical performance of nitrided iron materials. The novel design of a zinc barrier layer makes it possible for the IBS scaffold to have ultrathin struts and thick PDLLA coating of 12μm to maintain adequate scaffolding (125kPa) after 3months implantation while having a significantly shortened corrosion period (13months). The biocorrosion and bioresorption of the IBS scaffold could be effectively evaluated using Micro-CT, OCT and MRI methods. Although complete bioresorption of the corrosion products has not been observed yet, there are no identified biological problems for the IBS scaffold after implantation in rabbit abdominal aorta up to 13months. This study demonstrates that the IBS scaffold with novel design has significantly shortened corrosion period and less amount of corrosion products without causing any biological problems after implantation up to 13months, therefore is promising for coronary application.

EVALUATION OF INTIMAL HYPERPLASIA AND THROMBOSIS AFTER IMPLANTATION OF PLATELET GLYCOPROTEIN IIIa MONOCLONAL ANTIBODY-ELUTING STENT IN NEW ZEALAND WHITE RABBIT AORTA OR ILIAC ARTERIES

Since the percutaneous coronary intervention (PCI) was first introduced into China in 1984, this procedure has become widely accepted as an important step in coronary revascularization. This study aims to evaluate intimal hyperplasia and thrombosis after implantation of platelet glycoprotein IIIa monoclonal antibody (mAb)-eluting stent in the New Zealand white rabbit abdominal aorta or iliac artery by comparing CT angiography and pathological experiments. The antibody-eluting stents were prepared by the passive absorption method. Arterial intima in the stented segment and 0.5 cm adjacent to the stented site were observed and analyzed by scanning electron microscopy (SEM) and cross-sectional staining. Endothelialization and thrombosis on the stent surface were visualized by CT angiography and three-dimensional (3D) reconstruction technique in animals surviving from 1 to 12 weeks. Compared to stainless steel stents, the surface of antibody-eluting stents was covered with a complete endothelial layer after four weeks. Both CT angiography and pathological results showed intimal hyperplasia (p < 0.05) after 12 weeks. Therefore, pathological methods are the goldern standard for evaluation of intimal hyperplasia while CT angiography has a higher specificity in demonstrating the intimal changes after stent implantation for 12 weeks. The mAb-eluting stent has the potential to prevent thrombosis formation due to the interaction of stent with blood, and decreases the stenosis ratio by inhibiting neointima proliferation.

Long-lasting endothelium-dependent relaxation of isolated arteries caused by an extract from the bark of Combretum leprosum.

Objective To describe and to characterize the relaxing effect of an extract of the bark of Combretum leprosum on isolated arterial rings from different animals.Methods Rings (3 to 4mm) from rabbit, rat, or porcine arteries rings were suspended in an organ bath (Krebs, 37°C, 95%O2/5%CO2) to record isometric contractions. After the stabilization period (2 to 3 hours) contractions were induced by the addition of phenylephrine (0.1 to 0.3µM) or U46619 (10 to 100nM), and Combretum leprosum extract was added on the plateau of the contractions. Experiments were performed to determine the potency, duration, reversibility, and to get insights on the potential mechanism involved in extract-induced relaxations.Results In all rings tested, Combretumleprosum extract (1.5μg/mL) was able to cause relaxations, which were strictly endothelium-dependent. In rabbit or rat thoracic aorta rings, the relaxations were reversed by vitamin B12a or L-NG-nitroarginine. In porcine right coronary arteries and rabbit abdominal aorta, extract caused both L-NG-nitroarginine-sensitive and L-NG-nitroarginine-resistant relaxations. In rabbit thoracic aorta, the extract was relatively potent (EC50=0.20µg/mL) and caused relaxations; intriguingly the endothelium continued to produce relaxing factors for a long period after removing the extract. The magnitude of extract-induced relaxations was significantly reduced in the absence of extracellular Ca2+; in addition, the TRPs channels blocker ruthenium red (10µM) was able to revert extract-induced relaxations. Phytochemical analyses indicated that the extract was rich in polyphenol-like reacting substances.Conclusions Combretum leprosum extract contains bioactive compounds capable of promoting Ca2+-dependent stimulation of endothelial cells which results in a prolonged production of relaxing factors.

High speed intravascular photoacoustic imaging with fast optical parametric oscillator laser at 1.7 μm.

Intravascular photoacoustic imaging at 1.7 μm spectral band has shown promising capabilities for lipid-rich vulnerable atherosclerotic plaque detection. In this work, we report a high speed catheter-based integrated intravascular photoacoustic/intravascular ultrasound (IVPA/IVUS) imaging system with a 500 Hz optical parametric oscillator laser at 1725 nm. A lipid-mimicking phantom and atherosclerotic rabbit abdominal aorta were imaged at 1 frame per second, which is two orders of magnitude faster than previously reported in IVPA imaging with the same wavelength. Clear photoacoustic signals by the absorption of lipid rich deposition demonstrated the ability of the system for high speed vulnerable atherosclerotic plaques detection.

Effect of cystatin C on adventitia in restenosis after rabbit aorta angioplasty

Objective To investigate the effect of cystatin C (Cys C) on adventitia in rabbit abdominal aorta restenosis after angioplasty and its mechanism. Methods 48 New Zealand white rabbits were randomly divided into injury group (receiving balloon dilation of abdominal aorta), the treatment group (taking Cys C monoclonal antibody therapy) and the control group (receiving femoral artery puncture and catheter sheath without balloon dilation and intervention of Cys C monoclonal antibody injection), and each group had 16 rabbits.Peripheral vein blood was drawn to measure the serum level of cystatin C before and 8 h, 1 day, 1 week, 3 weeks, 6 weeks after the operation in all rabbits.After 6 weeks of operation, the abdominal aorta were taken and stained with HE.Vascular morphometry analysis and adventitial cell count were conducted.Smooth muscle actin (SM-actin) and proliferating cell nuclear antigen (PCNA) expressions in the adventitia were observed by immunohistochemical staining.The number of PCNA positive cell in the adventitia was counted and the PCNA proliferation index was calculated.The vascular remodeling index, vascular external elastic lamina area (EELA), internal elastic lamina area (IEIA) were used to evaluate the vascular remodeling and the residual stenosis and vascular cavity area was used to measure the vascular stenosis. Results Plasma Cys C level began to rise at 8h after operation and reached the peak at 1 week after operation, and continuously increased for 5 weeks in injury group, and reached to respectively at 3 weeks and 6 weeks after operation.The Cys C levels were significantly higher in injury group than in the treatment and control groups at different time points (all P<0.05). There were no significant differences in Cys C levels at different time points between the treatment group and the control group.The injury group showed that the number of PCNA positive cells was higher in injury group than in treatment and control groups, both P<0.05). Compared with the control group, the vascular luminal area, EELA and IELA were significantly increased (all P<0.05). After treated with the monoclonal antibody Cys C intervention, the treatment group showed that lumen area, vascular EELA, IELA was significantly decreased (P<0.05), and the vascular remodeling index and residual stenosis rate were decreased as compared with the injury group (0.871 vs.0.784, 33.1% vs.19.7%, both P<0.05). Correlation analysis showed that Cystatin C level was positively correlated with the vascular lumen area, neointimal area, internal elastic lamina area, external elastic lamina area and the number of PCNA positive cells (r=0.812, 0.797, 0.876, 0.932 and 0.822 respectively, all P<0.01). Conclusions Plasma Cys C level is increased in rabbit after abdominal aorta balloon injury and has a positive correlation with the severity of arterial stenosis.High Cys C level can induce adventitial fibroblast activation, proliferation, phenotype transformation and migration, and accelerate the processes of atherosclerosis and stenosis.Cys C level is the independent risk factor for abdominal aortic stenosis. Key words: Cyalones; Aorta, abdominal; Angioplasty

Enhanced bioactivity of Mg-Nd-Zn-Zr alloy achieved with nanoscale MgF2 surface for vascular stent application.

Magnesium (Mg) alloys have revolutionized the application of temporary load-bearing implants as they meet both engineering and medical requirements. However, rapid degradation of Mg alloys under physiological conditions remains the major obstacle hindering the wider use of Mg-based implants. Here we developed a simple method of preparing a nanoscale MgF2 film on Mg-Nd-Zn-Zr (denoted as JDBM) alloy, aiming to reduce the corrosion rate as well as improve the biological response. The corrosion rate of JDBM alloy exposed to artificial plasma is reduced by ∼20% from 0.337 ± 0.021 to 0.269 ± 0.043 mm·y(-1) due to the protective effect of the MgF2 film with a uniform and dense physical structure. The in vitro cytocompatibility test of MgF2-coated JDBM using human umbilical vein endothelial cells indicates enhanced viability, growth, and proliferation as compared to the naked substrate, and the MgF2 film with a nanoscale flakelike feature of ∼200-300 nm presents a much more favorable environment for endothelial cell adhesion, proliferation, and alignment. Furthermore, the animal experiment via implantation of MgF2-coated JDBM stent to rabbit abdominal aorta confirms excellent tissue compatibility of the well re-endothelialized stent with no sign of thrombogenesis and restenosis in the stented vessel.

Dose-dependent neuroprotection of delta-opioid peptide [D-Ala2, D-Leu5] enkephalin on spinal cord ischemia-reperfusion injury by regional perfusion into the abdominal aorta in rabbits

In our prior study, we showed that delta-opioid peptide [D-Ala(2), D-Leu(5)] enkephalin (DADLE), by regional perfusion into the abdominal aorta, could protect the spinal cord against ischemia-reperfusion (I/R) injury caused by aortic occlusion. However, the relative dose-response effects of DADLE still remain unclear. This study investigated whether DADLE has a dose-dependent efficiency on spinal cord I/R injury. New Zealand White rabbits were randomly divided into one of six groups: normal saline (NS; n= 8), DADLE (D) groups D0.0005 (n= 8), D0.005 (n= 8), D0.05 (n= 8), and D0.5mg/kg (n= 8), and a sham group (n= 6). In the NS and DADLE groups, spinal cord ischemia was induced by infrarenal aortic occlusion for 30minutes. During the occlusion, the same volume of NS or DADLE at the indicated doses was infused continuously through a catheter to the distally clamped abdominal aorta. Heart rate, blood pressure, and core temperature were monitored continuously to evaluate the potential adverse effects of DADLE. Neurologic behavioral function was assessed with the Tarlov scale system at 1, 6, 24, 48, and 72hours after reperfusion. Neuronal injury evaluation in the ventral horn of the gray matter was evaluated by counting the normal motor neurons at 72hours after reperfusion. The therapeutic benefits increased at the doses of DADLE from 0.0005 to 0.05mg/kg and decreased at 0.5mg/kg, whereas the hemodynamic parameter was suppressed temporarily at the dose of 0.5mg/kg. These data revealed that regional administration of DADLE through the abdominal aorta provided dose-dependent protection on spinal cord I/R in rabbits.

Experimental testing of a new generation of flow diverters in sidewall aneurysms in rabbits.

The development of new generation flow-diverting devices will improve the result of flow diversion in challenging aneurysms. The Flow-Redirection Endoluminal Device system is a dual-layer flow-diversion device. The purpose of this study was to evaluate the effectiveness and safety of the Flow-Redirection Endoluminal Device in a sidewall aneurysm model and in the abdominal aorta in rabbits. Single Flow-Redirection Endoluminal Devices were implanted in the right common carotid artery across sidewall, vein-pouch aneurysms and within the abdominal aorta in 22 New Zealand white rabbits and followed for 1 (n = 5), 3 (n = 5), 6 (n = 4), and 12 months (n = 8). Aneurysm occlusion was graded on a 3-point scale based on digital subtraction angiography (grade I, complete occlusion; grade II, near-complete occlusion; and grade III, incomplete occlusion). Toluidine blue and basic fuchsin staining was used for the evaluation of thrombus organization within the aneurysm and neck coverage with neointima. A scanning electron microscope was used for confirmation of the patency of branch vessels along with DSA. Grades I and II occlusion rates were noted in 19 (86%) and 3 (14%) aneurysms, respectively, which indicated a 100% rate of complete or near-complete occlusion. No parent artery and branch artery occlusion was shown on DSA. Histologic images indicated partial or complete intraluminal thrombus organization and neointima coverage across the aneurysm neck. A scanning electron microscope indicated that all the vessel branches along the length of the device remained patent. The Flow-Redirection Endoluminal Device in experimental aneurysms demonstrated high rates of progressive and complete aneurysm occlusion while preserving the patency of branch vessels.

Protective effect of delta opioid agonist [d-Ala2, d-Leu5] enkephalin on spinal cord ischemia reperfusion injury by regional perfusion into abdominal aorta in rabbits

[d-Ala2, d-Leu5] enkephalin (DADLE) has been reported to exhibit protective effects against hypoxic or ischemic induced brain insult. However its efficacy on the spinal cord ischemia-reperfusion injury remains unclear. Here we investigate whether DADLE could attenuate ischemia and reperfusion induced neural injury in the rabbit spinal cord. New Zealand white rabbits were subjected to spinal cord ischemia by infrarenal aortic occlusion for 30min. In the period of spinal cord ischemia, DADLE 0.5mg/kg or NS were infused continuously into the distal clamped abdominal aorta. The heart rate, blood pressure, and core temperature were monitored continuously during the whole experimental procedure. Then the neurological behavioral function was assessed with Tarlov scale system at 1h, 6h, 24h, 48h after reperfusion, and neuronal injury evaluation in the ventral horn of gray matter was measured by counting the normal motor neurons at 48h after reperfusion. Comparing with the control group, the Tarlov scores were significantly higher and the incidences of paraplegia were significantly lower in the DADLE group at four time-point recorded. In addition, the normal neurons numbers in the DADLE group were significant more than those in the control group at 48h after reperfusion. These results suggested that DADLE infused into the abdominal aorta during ischemia period could attenuate behavioral retardation and the loss of normal motor neuron induced by ischemia-reperfusion in rabbits.

β-adrenergic antagonists influence abdominal aorta contractility by mechanisms not involving β-adrenergic receptors.

β-adrenergic receptors (β-AR) are widely distributed in the cardiovascular system, where they considerably contribute to the control of its functions. β-blockers are commonly used in the treatment of disorders of the circulatory system. They act primarily by inhibiting cardiac β-receptors. However, there are also reports of pleiotropic action of β-blockers as well as of new compounds created to study β3 adrenergic receptors. The study aimed to investigate additional mechanisms of action of β-AR inhibitors in the rabbit abdominal aorta with emphasis on their action on α-adrenergic receptors and calcium influx. Responses to propranolol, betaxolol, metoprolol and SR59230A were evaluated in phenylephrine and PGF(2alpha) precontracted aortic rings. The effect of propranolol on the phenylephrine concentration-contraction curve was examined. Propranolol (≥ 10 μM) and SR59230A (≥ 0.1 μM) induced relaxations in phenylephrine-precontracted rings, while betaxolol and metoprolol had little effect. The β-AR inhibitors produced further contraction of tissues preincubated with PGF(2alpha), excluding SR59230A, which after initial contraction, elicited marked relaxation at a concentration above 1 ĕM. 100 μM of propranolol caused a significant rightward shift of the concentration-contraction curve to phenylephrine with no reduction in the maximum response. Incubation of aortic rings in phentolamine reduced the maximal contraction to propranolol; verapamil pretreatment by contrast enhanced contractile response. In conclusion, SR59230A and propranolol most probably act as α1-AR competitive antagonists in the presence of phenylephrine in rabbit abdominal aortic rings. After α-ARs blockade, propranolol exerts a weak relaxing activity connected with Ca2+ channel inactivation. SR59230A at a high concentration acts on the rabbit aorta by an additional mechanism needing further investigation.

Evaluation of Statin Therapy on Endothelial Function in Hypercholesterolemic Rabbits by Automatic Measurement of Arterial Wall Movement Using Ultrasound Images

The aim of this study was to evaluate arterial endothelial function, assessed as acetylcholine-mediated dilation (AMD), in a hypercholesterolemic atherosclerotic rabbit model to investigate the effects of atorvastatin in the atherosclerotic process, using a new computerized analysis model and ultrasound images. Twenty-seven rabbits were fed a high-cholesterol (2%) diet for 6 wk and then divided into three groups for an additional 9 wk: Group A received regular chow food, group B received a 2% cholesterol-rich diet plus atorvastatin drug, and group C received regular chow food plus atorvastatin. Ultrasound examinations of endothelial function of the rabbit abdominal aorta artery were performed immediately after the 6 weeks (0 wk) and then 3, 6 and 9 wk after that. For off-line analysis, a computerized analysis method for evaluating instantaneous changes in the wall of the rabbit abdominal aorta was used. As parameters of improvement resulting from treatment, endothelium-dependent acetylcholine-induced dilation and endothelium-independent nitroglycerin-induced dilation were evaluated in treated rabbits. Differences among groups were tested using analysis of variance. On histopathology, intima-media thickness decreased after treatment in all groups. There were no significant differences in arterial diameter and blood velocity changes among treated rabbits at 0, 3, 6 and 9 wk of treatment in all groups, except in end-diastolic velocity, radial strain percentage, pulse index and resistance index in group C. In group A, AMD did not significantly improve after 3, 6 and 9 wk, as compared with 0 wk. Atorvastatin treatment significantly increased AMD (18%) at 3 wk in group B, compared with week 0. AMD significantly increased after 3 (26%), 6 (124%) and 9 (182%) wk in group C, compared with 0 wk. It is concluded that the new automatic method enables accurate and repeated evaluation of endothelial function during the progression and regression of atherosclerosis. Also, the results obtained in this study indicate that short-term administration of atorvastatin can improve endothelial function in cholesterol-fed rabbits.

Atherosclerotic plaque identification by virtual histology intravascular ultrasound in a rabbit abdominal aorta model of vulnerable plaque

This study aimed to evaluate the utility of virtual histology intravascular ultrasound (VH-IVUS) for recognizing vulnerable plaque compared to histological pathological analysis. Four-month-old New Zealand rabbits (n = 16) were randomly divided into two groups: one fed a high-fat diet and subjected to balloon injury (experimental, n = 10) and one fed a high-fat diet alone (control, n = 6). Blood lipid profiles of overnight-fasted rabbits were measured at week 2 (beginning of study) and week 12 (end of study). At week 12, experimental group rabbits underwent IVUS under anaesthesia. Rabbits were sacrificed and a 5-cm segment of the abdominal aorta was removed. Arterial sections were subjected to pathological and immunohistochemical analyses. Serum lipid levels increased in all rabbits fed with high-fat diet, with low-density lipid cholesterol (LDL-C) levels increasing the most. Levels of six biomarkers (high sensitivity C-reactive protein, matrix metalloproteinase-3, interleukin [IL]-1, IL-10, tumour necrosis factor-α, and oxidized [ox]-LDL) showed no differences between the two groups at week 2, but were higher in the experimental group at week 12. A total of 276 atherosclerotic plaques in the experimental group were analysed. VH-IVUS had sensitivities of 87% and 92% for detection of noncalcified and calcified thin-cap fibroatheromas, respectively. VH-IVUS correctly identified 85% and 89% of noncalcified and calcified fibroatheromas, respectively. For detection of pathological intimal thickening, VH-IVUS showed a sensitivity of 79% and positive predictive value of 78%. Linear regression analysis showed a strong correlation between histology and VH-IVUS for the percent area of fibrous fibro-fatty tissue, necrotic calcified tissue, and confluent necrotic core. The intra-observer and inter-observer variability of the intimal and medial-adventitial boundaries was low. Endothelial injury followed by a high-fat diet in rabbits is a viable method for inducing atheroma, and VH-IVUS is a feasible, reproducible, and valuable means of vulnerable plaque identification invivo.

Combination of Periaortic Elastase Incubation and Cholesterol-Rich Diet: A Novel Model of Atherosclerosis in Rabbit Abdominal Aorta

Atherosclerosis, the leading cause of most cardiovascular disease, is a progressive multifaceted inflammatory disease characterized by extracellular matrix degradation and extensive remodeling of artery wall. However, its mechanism has not been completely understood, and animal models are useful to study its pathogenetic process. An analysis of literature on the nature of atherosclerosis indicates that focal accumulation of smooth muscle cells (SMCs) into the intima by plasma factors is fundamental to the entire process of plaque growth. In our previous study, vascular SMCs proliferation was obvious in elastase-induced aorta by day 15, which led to intimal hyperplasia and regression of rabbit aneurysm. Model induced by combination of balloon injury and an atherogenic diet in rabbits is the conventional, but most largely used experimental model of atherosclerosis. Since proliferation and accumulation of intimal SMCs are found in elastase-induced aorta, and hypercholesterolemia is usually induced by cholesterol-rich diets in rabbits, a novel atherosclerosis model may be induced by combination periaortic elastase incubation and cholesterol-rich diet.

Nonspecific Effects of Ligands on the β-Adrenergic Receptors in Rabbit Abdominal Aorta in vitro

The study was conducted on 30 New Zealand rabbits weighing 3-4 kg from which sample strips of the abdominal aorta were collected. The study investigated the in vitro reaction of rabbit aorta smooth muscle to ligands binding to beta-adrenergic receptors. The response of aortic strips to beta-adrenergic receptor agonists (dobutamine, isoproterenol, salbutamol) and the influence of beta-adrenergic receptor antagonists (propranolol, betaxolol) on contractile activity was determined. All tested agonists induced contraction of the rabbit abdominal aorta muscle in a concentration-dependent manner (dobutamine >> isoproterenol > salbutamol). Enhanced reaction to low concentrations of agonists (dobutamine, isoproterenol) after administration of propranolol and inhibition of contractility in the presence of high concentrations thereof (dobutamine, salbutamol) was observed. Maximal reaction to agonists decreased after betaxolol pretreatment. The results indicate that all the substances with beta-agonist activity also possess contracting properties (presumably by acting at alpha-adrenergic receptors), but are much weaker in the case of isoproterenol and salbutamol than for dobutamine. Propranolol and betaxolol reduce the contractile response of smooth muscle using probably other mechanisms than those associated with adrenergic receptors.

Antioxidant Effect of Captopril and Enalapril on Reactive Oxygen Species-Induced Endothelial Dysfunction in the Rabbit Abdominal Aorta

BackgroundReactive oxygen species (ROS) are known to be related to cardiovascular diseases. Many studies have demonstrated that angiotensin-converting enzyme inhibitors have beneficial effects against ROS. We investigated the antioxidant effect of captopril and enalapril in nitric oxide mediated vascular endothelium-dependent relaxations.Materials and MethodsIsolated rabbit abdominal aorta ring segments were exposed to ROS by electrolysis of the organ bath medium (Krebs-Henseleit solution) after pretreatment with various concentrations (range, 10-5 to 3×10-4 M) of captopril and enalapril. Before and after electrolysis, the endothelial function was measured by preconstricting the vessels with norepinephrine (10-6 M) followed by the cumulative addition of acetylcholine (range, 3×10-8 to 10-6 M). The relevance of the superoxide anion and hydrogen peroxide scavenging effect of captopril and enalapril was investigated using additional pretreatments of diethyldithiocarbamate (DETCA, 0.5 mM), an inhibitor of Cu/Zn superoxide dismutase, and 3-amino-1,2,4-triazole (3AT, 50 mM), an inhibitor of catalase.ResultsBoth captopril and enalapril preserved vascular endothelium-dependent relaxation after exposure to ROS in a dose-dependent manner (p<0.0001). Pretreatment with DETCA attenuated the antioxidant effect of captopril and enalapril (p<0.0001), but pretreatment with 3AT did not have an effect.ConclusionBoth captopril and enalapril protect endothelium against ROS in a dose-dependent fashion in isolated rabbit abdominal aortas. This protective effect is related to superoxide anion scavenging.

Comparison of the Effect of α1- and α2-Adrenoceptor Agonists and Antagonists on Muscle Contractility of the Rabbit Abdominal Aorta in vitro

The aim of the study was to demonstrate the effect of selected agonists and antagonists of alpha-adrenergic receptors on muscle contractility of the rabbit abdominal aorta in vitro with particular emphasis on alpha2-adrenergic receptor subtypes. The study was conducted on 30 New Zealand breed rabbits from which specimens of the abdominal aorta were collected. The sections were set up in an automatic water bath in a Krebs-Henseleit buffer at 37 degrees C. The experiments showed that alpha1-adrenergic receptors played the main role in the contractile response ofthe rabbit abdominal aorta. Stimulation of alpha1-adrenergic receptor by administration ofphenylephrine resulted in an increase in smooth muscle tonus ofthe rabbit abdominal aorta by an average of 4.75 mN. The reaction after stimulation of alpha2-adrenergic receptors by similar doses of their agonists was much weaker. Prolonged tissue response time and time needed to reach maximum tonus for alpha2-adrenergic receptor agonists were observed. The obtained results confirm the thesis that the alpha1-adrenergic receptor is the most important factor controlling the contractility of the rabbit abdominal aorta, but the alpha2-adrenergic receptor is also involved in maintaining muscle tissue tonus.

Assessment of atherosclerotic plaques in the rabbit abdominal aorta with interleukin-8 monoclonal antibody-targeted ultrasound microbubbles

In this study, we aimed to prepare a neovascularization-relevant inflammatory cytokine-targeted ultrasound contrast agent and apply it in the ultrasound imaging of atherosclerotic plaque. An interleukin-8 (IL-8) monoclonal antibody was conjugated to SonoVue microbubbles using the N-succinimidyl-3-(2-pyridyldithio)propionate cross-linking method. Then, a prepared IL-8-targeted contrast agent was used for contrast-enhanced ultrasound (CEU) to detect rabbit abdominal aorta atherosclerotic plaque and to investigate the imaging characteristics of atherosclerotic plaque with the contrast agent. We found that an IL-8 monoclonal antibody can be successfully coupled to SonoVue microbubbles with stable biological characteristics. CEU with this IL-8-targeted contrast agent can increase the atherosclerotic plaque detection sensitivity, with stronger echo, so that three more plaques were detected compared with using non-targeted SonoVue microbubbles. Thus, an inflammatory cytokine-targeting ultrasound contrast agent carrying IL-8 monoclonal antibody can provide unique advantages for researching the characteristics of atherosclerotic plaque.

Observation of a Long Primo Vessel in a Lymph Vessel from the Inguinal Node of a Rabbit

Though primo vessels are frequently found in the lymph near the abdominal aorta of rabbit by Alcian blue dye, the reproductions are still difficult to require considerable skills and technical know-how at dissected tissue of animal species. However, in the inguinal lymph node of a rabbit we found a long-type primo vascular system (LTP) dyed with Alcian blue, from an abdominal lymph vessel to an inguinal lymph node. The length of LTP was over an average length of 9.1 cm. The average diameters of the primo and the lymph vessels were about 23.9 μm and 242 μm, respectively. The primo vessels were not floating but adhered to lymph vessels with fascial connective tissue. These primo vessels might be a functional integration in the lymph system.

Role of α1-adrenergic receptor subtypes in contractility of the rabbit abdominal aorta in vitro

Investigation of the effect of α1-adrenergic receptor subtypes on the contraction of the abdominal aorta will allow for more effective treatment of hypertension by use of selective antagonists. The aim of the study was to evaluate the participation of α1-adrenergic receptor subtypes in the contractility of the aortic smooth muscle cells in rabbits. The in vitro experiments were performed in isolated tissue preparations from 30 adult female New Zealand rabbits. The abdominal aortic sections were placed in organ bath chambers and contracted with increasing doses of non-selective α1-adrenergic receptor agonist phenylephrine without pre-incubation or after incubation in α1-adrenergic receptor subtype-selective or non-selective antagonists. Separate sections were incubated with increasing concentrations of antagonists. Phenylephrine caused maximal rise in arterial smooth muscle tone to 4.75 ± 0.47 mN. The most potent in blocking phenylephrine induced contraction was 5-metylurapidil (α1A-adrenergic receptor antagonist) followed by phentolamine and prazosin (non-selective α1-adrenergic receptor antagonists); BMY 7378 (α1D-adrenergic receptor antagonist), cyclazosin and L-765.314 (α1B-adrenergic receptor antagonists) were less effective. All antagonists, except BMY 7378 elicited relaxation of non-precontracted aorta in dose dependent manner. Our results indicate that postsynaptic α1A receptors are the most potent in producing rabbit abdominal aorta contraction, while α1B and α1D subtypes are less effective.