Normal Rabbit Chow Research Articles

Changes of Hematological and Hemorheological Parameters in Rabbits with Hypercholesterolemia.

Hypercholesterolemia plays an important role in the development of atherosclerosis, leading to endothelial dysfunction, ischemic events, and increased mortality. Numerous studies suggest the pivotal role of rheological factors in the pathology of atherosclerosis. To get a more detailed hematological and hemorheological profile in hypercholesterolemia, we carried out an experiment on rabbits. Animals were divided into two groups: the control group (Control) was kept on normal rabbit chow, the high-cholesterol diet group (HC) was fed with special increased cholesterol-containing food. Hematological parameters (Sysmex K-4500 automate), whole blood and plasma viscosity (Hevimet-40 capillary viscometer), red blood cell (RBC) aggregation (Myrenne MA-1 aggregometer), deformability and mechanical stability (LoRRca MaxSis Osmoscan ektacytometer) were tested. The white blood cell and platelet count, mean corpuscular volume, and mean corpuscular hemoglobin were significantly higher in the HC group, while the RBC count, hemoglobin, and hematocrit values were lower than the Control data. Viscosity values corrected to 40% hematocrit were higher in the HC group. The RBC aggregation significantly increased in the HC vs. the Control. The HC group showed significantly worse results both in RBCs’ deformability and membrane stability. In conclusion, the atherogenic diet worsens the hematological and macro- and micro-rheological parameters, affecting blood flow properties and microcirculation.

Natural cocoa improves birth weight and viability of rabbit pups born to hypercholesterolemic mothers

BackgroundMaternal nutrition affects fetal growth and development in humans and animals. Low birth weight can be caused by maternal hypercholesterolemia and is associated with increased risk of cardiovascular and other metabolic diseases later in adult life. Cocoa powder is rich in flavonoids and reduces plasma cholesterol levels. The study investigated the effect of hypercholesterolemia and natural cocoa intake during pregnancy on the birth weight and viability of rabbit pups. MethodsHypercholesterolemic female New Zealand White rabbits were crossed with normocholesterolemic males and randomly grouped into 2 (n = 4 each). One group (HCC) received natural cocoa powder in their water in addition to high cholesterol diet during pregnancy, whereas the other (HC) received only water and high cholesterol diet. Litter size, birth weight and viability of pups were assessed and compared to a control group (NC) fed normal rabbit chow (n = 2). ResultsAverage litter sizes of hypercholesterolemic rabbits (HC and HCC groups) were 3, whereas that of control group, NC was 5. Mean birth weight of pups was significantly lower in offspring of HC (42.73 g, SD 8.47) and HCC (50.0 g, SD 3.54) as compared to NC (73.0 g, SD 5.37). Mortality of offspring was highest in HC group (58.3%) as compared to 50% in HCC. ConclusionsMaternal hypercholesterolemia during pregnancy reduces litter size, birth weight and viability of offspring in rabbits and these deleterious effects may be minimized by regular intake of natural cocoa. Although further studies in humans need to be conducted, the results of this study suggest the need to monitor maternal cholesterol levels during pregnancy and the effects on pregnancy outcomes and health of offspring later in life.

Effects of Lepidium sativum supplementation on growth and gonadotropins secretion in ovariectomized, estrogen-implanted rabbits

Objective: To test the effects of dietary supplementation of Lepidium sativum (LS) seed powder on growth performance and gonadotropins secretion in ovariectomized, estradiol- implanted rabbits. Methods: Ovariectomized, estradiol-implanted Chinchilla rabbits were assigned into four experimental groups: LS seed powder was included into normal rabbit chow at 0% (control), 5% (low), 7% (mid) and 10% (high) w/w. Experimental feed and water were given ad-libitum for 3 weeks. Weekly body weights and daily feed intake of rabbits were recorded. Twenty-one days post-feeding, blood samples were collected at 15-minute interval for 3 h (Period I) after which 2.5 μg gonadotropin-releasing hormone (GnRH) was injected intravenously and the sampling continued for another hour (Period II). Plasma was harvested and analyzed for luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by radioimmunoassay. Results: Feed intake was significantly (P

Macrophage content detection in an experimental rabbit model of atherosclerotic plaque by optical coherence tomography

To evaluate the feasibility of detecting macrophage content on atherosclerotic plaques by optical coherence tomography (OCT) technique. Thirty New Zealand white rabbits were equally divided into 3 groups at random: Control group (fed normal rabbit chow, n = 10); lipid diet group (fed regular chow supplemented with cholesterol, n = 10) and balloon injury+ lipid diet group (balloon catheter injury of the common carotid artery after 2 weeks lipid diet, n = 10). After 12 weeks, all rabbits underwent pharmacological triggering with Chinese Russell's viper venom (CRVV, 15 mg/kg, i.p.) and histamine (0.02 mg/kg, i.v.). Common carotid arteries were detected with OCT and the Movat pentachrome stain respectively. OCT and histological examination results were compared and the correlation was analyzed. The intra thickness measured by Movat pentachrome stain and by the OCT was (15.2 ± 0.9) µm and (20.2 ± 7.6) µm, the medial thickness was (434.2 ± 86.5) µm and (453.8 ± 87.2) µm, the plaque thickness was (330.2 ± 87.1) µm and (392.2 ± 134.5) µm, the fibrous cap thickness was (58.3 ± 5.6) µm and (61.2 ± 4.9) µm, respectively (all P > 0.05). The normalized standard deviation of the OCT signal (NSD) was compared with immunohistochemical detection. The OCT signal within the cap is relatively homogeneous for low macrophage density in high lipid diet group. For the raw OCT data, a correlation of r = 0.846 (P < 0.01) was found between OCT NSD and a CD68 area<10%, whereas for the base 10 logarithm OCT data, a correlation of r = 0.646 (P < 0.05) was found between OCT NSD and a CD68 area<10%. In balloon injury + high lipid diet group, the OCT signal within the cap was relatively heterogeneous for high macrophage content. For the raw OCT data, a correlation of r = 0.906 (P < 0.01) was found between OCT NSD and a CD68 area >10%, whereas for the base 10 logarithm OCT data, a correlation of r = 0.593 (P < 0.05) was found between OCT NSD and a CD68 area >10%. For the raw OCT signal NSD, a range of NSDs (7.12% to 7.35%) demonstrated 100% sensitivity and specificity (Kappa value 1.0) for differentiating caps containing >10% CD68 staining. For the base 10 logarithm OCT signal, NSD values ranging from 7.81% to 7.92% provided 70% sensitivity and 75% specificity (value 0.44) for identifying caps containing >10% CD68 staining. OCT is an effective tool to determine macrophage content in this model. OCT imaging can clearly visualize different types of atherosclerotic plaques and provide detailed information on plaque characteristics.

Simvastatin Decreases Stent‐Induced In‐Stent Restenosis Rate Via Downregulating the Expression of PCNA and Upregulating that of p27kip1

The inhibition of the proliferation and migration of vascular smooth muscle cells (VSMC) is one cholesterol-independent effect of statins that could lower the rate of in-stent restenosis (ISR), even if the exact mechanism remains unclear. The aim of this study was to explore the exact inhibitory mechanisms of simvastatin on ISR in vivo. Forty-five rabbits were randomized into 3 feeding groups of equal size (n=15): normal rabbit chow (normal group), a high-cholesterol diet (control group), and a simvastatin-enriched high-cholesterol diet (simvastatin group). Balloon de-endothelialization was first performed in the control and simvastatin groups after 3 days, followed by stent deployment at week 14. All rabbits were killed at week 18, and the histological changes of the ISR segments were observed. The expressions of cyclin-dependent kinase inhibitor p27 (p27kip1), proliferating cell nuclear antigen (PCNA), and α-smooth muscle (α-SM) actin were measured. In the simvastatin group compared to the control group, the neointimal thickness, neointimal area, and degree of stenosis decreased, while the residual lumen area increased significantly (P<0.05). Moreover, the expression of α-SM actin in the control group decreased by 55.4% compared to the normal group, while it increased by 29.7% with respect to the simvastatin group (P<0.05). Finally, the expression of p27kip1 increased, while that of PCNA decreased significantly in the simvastatin group compared to the control group (P<0.05). Simvastatin may inhibit VSMC phenotype modulation and proliferation by downregulating the expression of PCNA and upregulating that of p27kip1.

Monteleucast and Zileuton Retard the Progression of Atherosclerosis via Down Regulation of the Inflammatory and Oxidative Pathways

Background: Atherosclerosis and its thrombotic complications are responsible for remarkably high numbers of deaths. Leukotrines are involved in different stages of atherosclerosis. Therefore this study was undertaken to evaluate the effect of montelukast and zileuton on the progression of atherosclerosis. Materials and methods: Thirty-five male rabbits were used in this study. These animals randomized into 5 groups (7 rabbits each). Rabbits in first group were maintained on normal rabbit chow diet and used as normal diet control group (NC). While the rabbits in other four groups were fed on atherogenic diet (2% cholesterol) for 8 weeks. The second group, Atherogenic Control Group (AC) rabbits received atherogenic diet alone. Third group, Positive Control Group (PC) rabbits received atherogenic diet and ethanol as vehicle. Forth group, Montelukast Treated Group (MT) rabbits received montelukast 1.5 mg per kg daily and the fifth group, Zileuton Treated Group (ZT) rabbits received zileuton 150 mg per kg daily. At the end of 8th weeks animals were sacrificed, blood sample was collected to measure the following parameters: lipid profile, plasma GSH, MDA, and hsCRP. Immunohistochemical analysis (VCAM-1, MCP-1, TNF-α, and IL17) and histopathologic assessment of aortic atherosclerotic changes were also performed. Results: Compared to NC, levels of lipid profile, atherogenic index, hsCRP, and MDA are increased while GSH were decreased in animals on atherogenic diet (p<0.001). There was statistically insignificant difference in the study parameters between positive control groups, when compared with those on atherogenic diet. Immunohistochemical analysis showed that expression of aortic VCAM-1, MCP-1, TNF-α and IL17 were significantly increased in AC group compared to NC group (p<0.001). Histopathologic finding showed that animals on atherogenic diet have significant atherosclerotic lesion compared to NC group. Compared to AC group both montelukast and zileuton do not have significant effect on lipid profile. Montelukast and zileuton cause statistically significant reduction in hsCRP and MDA, (p<0.001). Montelukast and zileuton treatment caused statistically significant, increase in plasma levels of GSH and reduced plasma MDA level (p<0.001). Both montelukast and zileuton treatment significantly reduced the expression of aortic VCAM-1, MCP-1, TNF-α and IL17 (p<0.001). Histopathologic examination of aortic arch showed that both montelukast and zileuton significantly reduced atherosclerotic lesion (p<0.001). Conclusion: Both montelukast and zileuton reduce lipid peroxidation, systemic inflammation and aortic expressions of inflammatory markers used in this study and reduced the progression of atherosclerosis.

Effect of methanolic extract of Piper sarmentosum leaves on neointimal foam cell infiltration in rabbits fed with high cholesterol diet.

Previous research has shown the beneficial effects of aqueous extract of Piper sarmentosum (P.s) on atherosclerosis. The first stage in atherosclerosis is the formation of foam cell. The aim of this study was to investigate the effect of the methanol extract of P.s on fatty streaks by calculating neointimal foam cell infiltration in rabbits fed with high cholesterol diet. Thirty six male New Zealand white rabbits were divided equally into six groups: (i) C: control group fed normal rabbit chow; (ii) CH: cholesterol diet (1 % cholesterol); (iii) PM1: 1 % cholesterol with methanol extract of P.s (62.5 mg/kg); (iv) PM2: 1 % cholesterol with methanol extract of P.s (125 mg/kg); (v) PM3: 1 % cholesterol with methanol extract of P.s (250 mg/kg); (vi) SMV group fed 1 % cholesterol supplemented with Simvistatin drug (1.2 mg/kg). All animals were treated for 10 weeks. At the end of the treatment, the rabbits were fasted and sacrificed and the aortic tissues were collected for histological studies to measure the area of the neointimal foam cell infiltration using software. The thickening of intima ratio of atherosclerosis and morphological changes by scanning electron microscope were measured. The results showed that the atherosclerotic group had significantly bigger area of fatty streak compared to the control group. The area of fatty streak in the abdominal aorta was significantly reduced in the treatment groups which were similar with the SMV group. Similarly, there was a reduction in the number of foam cell in the treatment groups compared to the atherosclerotic group as seen under scanning microscope. In conclusion, histological study demonstrated that the methanol extract of the P.s could reduce the neointimal foam cell infiltration in the lumen of the aorta and the atherosclerotic lesion.

Changes in the vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and c-reactive protein following administration of aqueous extract of piper sarmentosum on experimental rabbits fed with cholesterol diet.

BackgroundInflammation process plays an important role in the development of atherosclerosis. Hypercholesterolemia is one of the major risk factors for atherosclerosis. The present study aimed to evaluate the effect of aqueous extract of Piper sarmentosum (P.s) on inflammatory markers like vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and C-reactive protein (CRP).MethodsForty two male New Zealand white rabbits were divided equally into seven groups; (i) C- control group fed normal rabbit chow (ii) CH- cholesterol diet (1%cholesterol) (iii) X1- 1% cholesterol with water extract of P.s (62.5 mg/kg) (iv) X2- 1% cholesterol with water extract of P.s (125 mg/kg (v) X3- 1% cholesterol with water extract of P.s (250 mg/kg) (vi) X4- 1% cholesterol with water extract of P.s (500 mg/kg) and (vii) SMV group fed with 1% cholesterol supplemented with simvistatin drug (1.2 mg/kg). All animals were treated for 10 weeks. Blood serum was taken for observing the inflammatory markers at the beginning and end of the experiment.ResultsRabbits fed with 1% cholesterol diet (CH) showed significant increase in the level of VCAM-1, ICAM-1 and CRP compared to the C group. The levels of VCAM-1, ICAM-1 and CRP in the 1% cholesterol group and supplemented with P.s (500 mg/kg) were significantly reduced compared to the cholesterol group. Similar results were also reported with simvistatin group.ConclusionThese results suggest that the supplementation of Piper sarmentosum extract could inhibit inflammatory markers which in turn could prevent atherosclerosis.

Aqueous extract of Piper sarmentosum decreases atherosclerotic lesions in high cholesterolemic experimental rabbits.

BackgroundPiper sarmentosum (P.s) has flavonoid component in its leaves which has antioxidative effect. To date, its effect on atherosclerosis has not been studied histologically.AimThe study aimed to investigate the effect of P.s on atherosclerotic changes in hypercholesterolemic rabbits.MethodsForty two male New Zealand white rabbits were divided into seven groups. C - control group fed normal rabbit chow, CH - cholesterol diet (1% cholesterol), W1 - 1% cholesterol with water extract of P.s (62.5 mg/kg), W2 - 1% cholesterol with water extract of P.s (125 mg/kg), W3 - 1% cholesterol with water extract of P.s (250 mg/kg), W4 - 1% cholesterol with water extract of P.s (500 mg/kg) and Smv - 1% cholesterol supplemented with simvistatin drug (1.2 mg/kg). All rabbits were treated for 10 weeks. Following 10 weeks of supplementation, the animals were sacrificed and the aortic tissue was taken for histological study.ResultsRabbits fed only with high cholesterol diet 1% cholesterol (CH) showed focal fatty streak lesions compared to the C group and 1% cholesterol supplemented with simvistatin drug (Smv) group. Atherosclerotic lesions in the 1% cholesterol group supplemented with P.s (500 mg/kg) i.e. W4 group showed significant reduction (30 ± 6.0%, p < 0.05) in fatty streak compared to the high cholesterol group (85.6 ± 4.1%) under Sudan IV stain. The atherosclerotic lesions under transmission electron microscope showed reduction in foam cells in the treatment groups compared to the CH groups.ConclusionAdministration of P.s extract has protective effect against atheroscleros

VON WILLEBRAND FACTOR, C-REACTIVE PROTEIN, NITRIC OXIDE, AND VASCULAR ENDOTHELIAL GROWTH FACTOR IN A DIETARY REVERSAL MODEL OF HYPERCHOLESTEROLEMIA IN RABBIT

Endothelial dysfunction is considered a sign of the early vascular changes preceding atherosclerosis. We studied the alteration of von Willebrand Factor (vWF), C - reactive protein (CRP), nitrite and Vascular Endothelial Growth Factor (VEGF) in a dietary reversal model of hypercholesterolemia in rabbit. This project was designed in two phases. In phase I, male rabbits (n = 11) were fed a 1% high cholesterol diet for 30 days. Then the diet was replaced with normal rabbit chow for other 30 days (cholesterol withdrawal phase, phase II). To compare the fatty streak formation with normal condition, a control group (n = 6) received normal diet during the study. The serum lipid levels, vWF, CRP, nitrite, and VEGF were measured before the experiment and by the end of each phase. Fatty streak formation in the walls of the aortas in both groups (high cholesterol diet and control group) was determined using intima thickness/media thickness (IMT) ratio. The results indicate that the level of cholesterol, Low Density Lipoproteins (LDL), vWF and CRP increased significantly in phase I, and decreased after hypercholesterolemic diet withdrawal (p < 0.05). No statistically significant changes were found in VEGF levels but the serum level of nitrite increased significantly during both phases of the study (p < 0.05). The IMT ratio in the walls of aortas was significantly different between the groups in both phases of studies (p < 0.05). There was a significant correlation between nitrite and cholesterol levels in both phases (r = 0.62 and r = 0.98, p < 0.05). Nitrite concentration also correlated with IMT ratio in both phases of the study (r = 0.75 and r = -0.99, p < 0.05). vWF did not correlate with cholesterol but it correlated with IMT ratio in both phases of the study (r = 0.87 and r = 0.84, p < 0.05). CRP only correlated with cholesterol in the first phase (r = 0.91, p < 0.05). Among the endothelial biomarkers, vWF was found to be a biological marker for identifying the risk of developing atherosclerosis; however a single biomarker may not provide appropriate information.

Lipoprotein inflammatory properties and serum amyloid A levels but not cholesterol levels predict lesion area in cholesterol-fed rabbits

Rabbits on a 1% cholesterol diet received injections of vehicle with or without D-4F or L-4F. After 1 month, the percent of aorta with atherosclerotic lesions was 24 +/- 15% (vehicle), 10 +/- 6% (D-4F) (P < 0.01 vs. vehicle), and 13 +/- 9% (L-4F) (P < 0.05 vs. vehicle). Inflammatory indexes for HDL and LDL were determined by measuring monocyte chemotactic activity after adding rabbit lipoproteins to human endothelial cells. HDL-inflammatory index (HII) and LDL-inflammatory index (LII), respectively, were 1.39 +/- 0.24; 1.35 +/- 0.29 (vehicle), 0.67 +/- 0.26; 0.63 +/- 0.38 (D-4F) (P < 0.001 vs. vehicle), and 0.67 +/- 0.2; 0.68 +/- 0.32 (L-4F) (P < 0.01 vs. vehicle). Serum amyloid A (SAA) levels were 95 +/- 39, 8 +/- 22, and 7 +/- 19 mug/ml, respectively, for vehicle, D-4F, and L-4F (P < 0.001 vs. vehicle). There was no correlation between lesion area and total plasma or HDL-cholesterol levels. In contrast, there was a positive correlation with HII, LII, and SAA (P = 0.002, P = 0.0026, P = 0.0079, respectively). HII correlated closely with SAA levels (r = 0.6616; r(2) = 0.4377, P < 0.0001). Thus, HII, LII, and SAA are better predictors of lesion area than are total plasma or HDL-cholesterol levels in cholesterol-fed rabbits.

Abstract 1143: Imaging of Vasa Vasorum in Atherosclerotic Plaque with 99m Tc-labeled single chain-VEGF

Introduction: Adventitial vasa vasorum proliferation and neointimal neovascularization are associated with intraplaque hemorrhage, expansion of necrotic core and hence plaque vulnerability. Increased expression of VEGF and its receptors accompany neoangiogenic process. We used 99m Tc -labeled single chain VEGF (TcV) for developing potentially noninvasive imaging modality in experimentally induced aortic atherosclerotic lesion. Methods : Noninva-sive radionuclide imaging was performed with TcV (6.85 ±0. 27 mCi) in 6 NZW rabbits receiving high cholesterol diet (0.2% cholesterol, 4% fat) for one year and compared with 3 control rabbits receiving normal rabbit chow. Four hours after intravenous administration of TcV, micro SPECT/microCT imaging was performed for in vivo localization of tracer activity. Aortas were then explanted, and gamma counted for determination of % injected dose per gram (%ID/g). The aortas were then submitted for histopathologic characterization. Results : The uptake in thoracic aorta was clearly visualized non-invasively by TcV in vivo imaging in 4 of 5 rabbits in hypercholesterolemic rabbits, but not in the control animals. The %ID/g of each parts of aorta in hypercholesterolemic rabbits (Arch : 0.036 ± 0.020 %, Thoracic : 0.026 ± 0.012 %, Abd : 0.019 ± 0.009 %) was about 2.5-fold higher than that in control group (Arch : 0.014 ± 0.004 %, Thoracic : 0.009 ± 0.003 %, Abd : 0.009 ± 0.003 %) (figure a ). Ex vivo images of each group are shown as figure b . Conclusions : This preliminary study suggests a potentially novel strategy for non-invasive imaging of neoangiogenesis in atherosclerotic plaque and may allow identification of unstable plaques.

Long-term effect of experimental hypercholesterolemia on cavernosal tissues

Objectives To determine the effect of long-term experimental hypercholesterolemia on cavernosal tissues and to evaluate whether these alterations are reversible after improvement of hypercholesterolemia. Methods Thirty-seven New Zealand male rabbits with a mean age of 5 to 6 months and a weight of 2 to 2.5 kg were included in this study. The control group (group 1, n = 7) was fed with normal standard rabbit chow for 24 weeks, the hypercholesterolemia group (group 2, n = 17) was fed with a 1% pure cholesterol diet for 24 weeks, and the reversibility group (group 3, n = 13) was fed first with the 1% pure cholesterol diet for 24 weeks and then with normal standard rabbit chow for 12 weeks. The basal and 24-week serum lipid profiles of all groups and the 36-week serum lipid profiles of group 3 were measured. Core tissue samples 4 mm in diameter taken from formalin-fixed, paraffin-embedded tissue blocks of rabbit corpus cavernosum were examined for Masson trichrome histochemically and desmin and smooth muscle actin by the tissue array method using immunohistochemistry. Results Hypercholesterolemia was observed in groups 2 and 3 at 24 weeks compared with group 1. In group 3, at 36 weeks, the cholesterol levels were decreased. A statistically significant ( P <0.05) irreversible decrease was observed in smooth muscle actin level in group 3 (reversibility group) by immunohistochemical analysis. The decrease in desmin was reversible, and no significant difference was observed in collagen among the three groups. Conclusions Long-term chronic effects of experimental hypercholesterolemia on cavernosal smooth muscles might be irreversible and this might alter erectile function.

Inhibition of cholesteryl ester transfer protein activity by JTT-705 increases apolipoprotein E-containing high-density lipoprotein and favorably affects the function and enzyme composition of high-density lipoprotein in rabbits.

Inhibition of cholesteryl ester transfer protein (CETP) is an efficient way to increase high-density lipoprotein (HDL) levels in humans. We investigated the effects of the inhibition of CETP activity by a CETP inhibitor, JTT-705, on the function and composition of HDL particles. Japanese white rabbits were fed either normal rabbit chow LRC-4 (n=10) or a food admixture of LRC-4 and 0.75% JTT-705 (n=10) for 7 months. JTT-705 significantly inhibited CETP activities, increased HDL cholesterol (HDL-C) levels and the ratio of HDL2-C/HDL3-C, and decreased the fractional esterification rate of cholesterol in HDL, indicating preferentially increased large HDL particles. Treatment with JTT-705 increased all of the 3 charge-based HDL subfractions as determined by capillary isotachophoresis: fast-migrating, intermediate-migrating, and slow-migrating HDL. The percentage of slow HDL, ie, apolipoprotein E (apoE)-containing HDL and levels of apoE in HDL fraction, was also increased. JTT-705 treatment increased serum paraoxonase activity and HDL-associated platelet-activating factor acetylhydrolase activity, but decreased the plasma lysophosphatidylcholine concentration. Inhibition of CETP activity by JTT-705 not only increased the quantity of HDL, including HDL-C levels and charge-based HDL subfractions, but also favorably affected the size distribution of HDL subpopulations and the apolipoprotein and enzyme composition of HDL in rabbits.

W05.155 The role of T-cadherin in cell adhesion and migration, interaction with LDL and signalling

The purpose of this study was to test the hypothesis that plasma renin activity (PRA) is a risk factor for cardiovascular disease. Four groups of New Zealand rabbits were used to study the effects of PRA and hypertension on atherogenesis. Control groups were fed normal rabbit chow (Group I), or normal chow supplemented with 0.25% cholesterol (Group III) Group II animals were fed normal chow, had a clip placed around the left renal artery and were contralaterally nephrectomized (one-kidney-one-clip, 1K-1C). The renal arteries and kidneys of Group IV animals, which were fed a cholesterol diet, were manipulated similarly. Blood pressure and blood chemistry measurements were performed periodically over a 7-month period. The blood pressure was unaffected by either diet; however, PRA and aldosterone levels were greatly reduced in the 1 K-1 C groups (Groups II and IV). No atheroma were observed in any of the animals consuming the normal diet (Groups I and II) despite sharply elevated blood pressure in the Group II animals. Medial hypertrophy of small muscular arteries was observed in several Group II animals. All of the animals fed the atherogenic diet showed extensive aortic atheromata. There was, however, a significantly smaller lesion index for the normotensive cholesterol-fed animals (Group III) than those with increased blood pressure (Group IV). Likewise, microscopic evaluation of the aorta, coronary arteries, renal arteries, and kidneys mirrored this difference in the vascular involvement between the animals of Groups III and IV. We conclude that neither relatively high nor low PRA levels affect the development of atherosclerosis or other cardiovascular lesions. However, hypertension with a concomitantly high cholesterol diet acts synergistically in exacerbating atherogenesis.

Inhibition of cholesteryl ester transfer protein increases serum apolipoprotein (apo) A-I levels by increasing the synthesis of apo A-I in rabbits

Background: Inhibition of cholesteryl ester transfer protein (CETP) is an effective way to increase HDL levels in animals and humans. The effects of a CETP inhibitor, JTT-705, on the in vivo kinetics of apolipoprotein (apo) A-I and apo A-I gene expression in the liver and intestine were investigated. Methods: Japanese White rabbits were randomly fed normal rabbit chow LRC-4 ( n=10, control) or a food admixture of LRC-4 and 0.75% JTT-705 ( n=10, treated) for 7 months. An in vivo kinetics study of apo A-I was performed by injecting rabbit 125 I -apo A-I, and apo A-I mRNA levels were quantified by RT-PCR. Results: JTT-705 significantly inhibited CETP activities, increased serum levels of HDL-cholesterol (C), HDL 2-C, HDL-phospholipid, and apo A-I, and decreased HDL-triglyceride levels. The synthetic rate of apo A-I was higher in the treated rabbits than in control rabbits (13.7±2.6 versus 9.5±1.3 mg/kg per day, P<0.05), while the fractional catabolic rate was similar in the two groups. JTT-705 increased apo A-I mRNA levels in the liver without affecting those in the intestine. Conclusion: Inhibition of CETP activity by JTT-705 increases HDL levels by increasing the synthesis of apo A-I, suggesting that it could be a promising therapeutic approach for atherosclerosis.

Atorvastatin prevents glomerulosclerosis and renal endothelial dysfunction in hypercholesterolaemic rabbits.

Numerous studies have shown that elevated plasma cholesterol can exacerbate renal disease. However, the effect of lipids on renal structure and vascular function in normal kidneys is less well established. Therefore, the aim of this study was to evaluate the impact of hypercholesterolaemia on glomerular structure and vascular reactivity of segmental arteries in rabbits. In addition, we also studied whether or not atorvastatin can prevent these structural and vascular alterations in hypercholesterolaemic rabbits. Male New Zealand rabbits were fed either a normal rabbit chow or a diet containing 1% cholesterol and treated or not with atorvastatin (1 mg/kg/day) for 12 weeks. Dose-response curves to acetylcholine (10(-9)-10(-4) mol/l) and sodium nitroprusside (10(-9)-10(-4) mol/l) were studied in segmental arteries in the presence or absence of the thromboxane A2/PGH2 receptor antagonist ifetroban (10(-5) mol/l). Glomerular size and structure were also evaluated. Compared with control animals, hypercholesterolaemic rabbits presented glomerular hypertrophy and several types of injuries (capillary collapse, hyalinosis and alterations of Bowman's capsule), suggesting diffuse glomerulosclerosis. Segmental arteries also showed relaxing responses to acetylcholine and sodium nitroprusside which were lower than and similar to, respectively, those of control animals. The presence of ifetroban improved the acetylcholine response only in hypercholesterolaemic rabbits. Atorvastatin treatment prevented vascular and most glomerular changes associated with hypercholesterolaemia even in the presence of very high cholesterol levels. Atorvastatin exerts a protective effect on renal damage associated with hypercholesterolaemia even in the presence of deleterious levels of plasma cholesterol.

Intracavernosal injections of vascular endothelial growth factor protects endothelial dependent corpora cavernosal smooth muscle relaxation in the hypercholesterolemic rabbit: a preliminary study.

Atherosclerosis is a major risk factor for erectile dysfunction, and loss of endothelium-dependent vasodilation appears early in the development of this disorder. Nitric oxide (NO) appears to be the principle mediator of erectile function and is generated in part by the sinusoidal endothelium. Vascular endothelial growth factor (VEGF) is an angiogenic growth factor and an endothelial cell-specific mitogen and the actions of VEGF are coupled to NO. In this preliminary study, we investigated whether VEGF could be used to protect endothelial dependent cavernosal relaxation from the atherosclerotic injury induced by a hypercholesterolemic diet.Two groups of New Zealand white adult male rabbits received a 1% cholesterol diet for four weeks, and two groups consumed normal rabbit chow. Half of the rabbits consuming the 1% cholesterol diet received weekly penile injections of 0.3 mg VEGF (n=8), and half injections of normal saline (n=8). Rabbits fed normal chow followed a similar protocol, half received weekly penile injections of 0.3 mg VEGF (n=6) and half were given weekly penile injections of normal saline (n=6). Isometric tension studies (with norepinephrine, acetylcholine, sodium nitroprusside and histamine) were performed on isolated strips of corpora cavernosa. The degree of corporal smooth muscle relaxation in response to ACH and SNP administration was recorded and compared. Significant elevation in serum total cholesterol levels occurred in rabbits receiving 4 weeks of the 1% cholesterol diet (727+/-75.6 mg/dl vs 38.7+/-5.53 mg/dl) P<0.01. There were no significant differences in cavernosal contraction in any group, while cavernosal smooth muscle from rabbits on normal chow retained the ability to relax in response to ACH and SNP in tissue bath. The hypercholesterolemic rabbits receiving VEGF had a significantly higher maximal per-cent relaxation to ACH (111+/-28.9) compared to the hypercholesterolemic rabbits that received NS (77+/-23.1, P<0.001). This difference in percent maximal relaxation to SNP was also present for hypercholesterolemic/VEGF rabbits (129.4+/-24) versus the hypercholesterolemic/NS rabbits (115.0+/-18, P=0.033). In conclusion, intracavernosal injections of VEGF appear to protect corporal endothelium from hypercholesterolemia induced injury, thus preserving endothelial dependent corporal smooth muscle relaxation in hypercholesterolemic rabbit.

Dietary copper supplementation reduces atherosclerosis in the cholesterol-fed rabbit

There has been considerable debate about how copper status may affect the biochemical and cellular processes associated with atherogenesis. In the present study we have attempted to address this issue directly by investigating the effects of dietary copper supplementation on processes likely to contribute to atherogenesis, using the cholesterol-fed New Zealand White rabbit model. Age matched rabbits ( n=16) were fed a 0.25–1% cholesterol diet to maintain plasma cholesterol concentrations at approximately 30 mmol/l. Eight of these animals also received 0.2% copper acetate. Control animals ( n=8) received rabbit chow without supplements. After 13 weeks on the experimental diets the animals were killed. Integrated cholesterol levels were similar for the cholesterol-fed animals (31.1±2.5 vs. 29.9±1.9 mmol/l weeks; P>0.05). Although integrated plasma copper levels were higher in the animals receiving the copper supplements, these did not differ significantly (19.0±4.8 vs. 15.1±2.9 μmol/l weeks; P>0.05). Tissue concentrations of copper were higher in the copper fed animals compared to those on cholesterol alone in aortic (4.0±0.75 vs. 1.8±0.2 μg/g wet tissue; P<0.05), carotid artery (11.4±3.5 vs. 4.9±0.9 μg/g wet tissue; P<0.05), and hepatic (332.5±28.6 vs. 3.3±1.1 μg/g wet tissue; P<0.0001) samples. The concentration of copper within the carotid artery was also significantly higher than that within the aorta (7.5±1.8 vs. 2.4±0.4 μg/g wet tissue; P<0.05). In animals fed a normal rabbit chow aortic, carotid and hepatic copper concentrations were 3.7±0.8, 9.4±3.4, and 5.0±1.6 μg/g, respectively. These values did not differ significantly from the cholesterol-fed animals ( P>0.05). Plasma concentrations of caeruloplasmin, the major copper carrying protein, were estimated as plasma ferroxidase activity and were similar for the groups ( P>0.05), as were aortic superoxide dismutase activity levels ( P>0.05). Copper supplementation was associated with increased mononuclear cell adhesion to the endothelium of the carotid endothelium, with 2.6±0.3 adherent monocytes/1000 endothelial cells in the cholesterol plus copper-fed animals compared to 1.3±0.3 in the cholesterol-fed group ( P=0.0.0006), and 0.1±0.1 in the control animals ( P<0.002). This may reflect the higher concentrations of copper found within the carotid artery. Histology of the thoracic aorta at the level of the third and sixth intercostal arteries, showed that copper supplementation was associated with significantly smaller intimal lesions ( P<0.05 and P<0.01, respectively). These data suggest that copper supplements possibly inhibit the progression of atherogenesis.

Antiatherogenic effect of angiotensin converting enzyme inhibitor (benazepril) and angiotensin II receptor antagonist (valsartan) in the cholesterol-fed rabbits

The purpose of this study was to determine whether an angiotensin converting enzyme (ACE) inhibitor, benazepril, and an angiotensin receptor antagonist, valsartan, would decrease atherosclerotic severity in cholesterol-fed rabbits. Male rabbits were fed either: (a) normal rabbit chow; (b) 2% cholesterol diet; (c) 2% cholesterol diet supplemented by benazepril (3 mg/kg per day, subcutaneous injection); or (d) 2% cholesterol diet supplemented by valsartan (1 mg/kg per day, subcutaneous injection). After 12 weeks, the arteries were harvested for histomorphometry and immunohistochemistry. We observed that decreases in serum triglyceride (TG) and total cholesterol (TC) and ACE activity with benazepril-treatment were more than 60, 30, and 84%, respectively, in comparison with the cholesterol group; with valsartan-treatment, TG levels were 53% lower than in the cholesterol group, however, there was no significant difference in TC and ACE activity. The percentage of aortic surface atherosclerotic area, intimal thickness and the ratio of aortic intimal area to medial area were about 40% lower in the benazepril-treated group in comparison with those of the cholesterol group; the difference was more than 60% in the thoracic aorta. The valsartan-treated group had 23% less atherosclerotic area, less effective than benazepril treatment. The percent of PCNA-positive cells and the number of intimal proliferative cells/mm 2 were significantly less in the benazepril-treated group compared with the cholesterol group (by 55 and 63%); these parameters were 35 and 17% lower, respectively, with valsartan. The ratio of proliferating macrophages to smooth muscle cells (SMCs) was 3:1 in the cholesterol group, 1:1 in the benazepril and 2:1 in the valsartan-treated group. These results indicate that benazepril could reduce atherosclerotic progression by decreasing macrophage proliferation and accumulation in the arterial wall. The mechanisms for reducing atherosclerotic progression by benazepril and valsartan may be related to reduction of TG and blockade of the angiotensin II action.