Glutamine prevents gastric oxidative stress in an animal model of portal hypertension gastropathy

Background and rationale. Portal hypertension (PHI) is a clinical syndrome characterized by increases of the blood flow and/or of the vascular resistance in the portal system. A direct consequence of PHI can appearance different lesions on the gastric mucosa and submucosa, cumulatively termed portal hypertensive gastropathy (PHG). Aims. To investigate the effects of glutamine on oxidative stress in an experimental model of PHG induced by partial portal vein ligation (PPVL).Material and methods. Portal pressure, transaminase and alkaline phosphatase activity were quantified. Gastric tissue damage was assessed by histological analysis. Oxidative stress was measured by quantification of cytosolic concentration of thiobarbituric acid reactive substances (TBARS), hydroperoxide-initiated chemiluminescence (QL), and nitric oxide (NO) production. Moreover, activities of the antioxidant enzymes superoxide dismutase (SOD), glutathione pe-roxidase (GPx), and catalase (CAT) were analyzed.Results. Transaminase and alkaline phosphatase activities were not significantly modified by PPVL, indicating absence of liver injury. Histological analysis of gastric sections showed a lost of normal architecture, with edema and vasodilatation. TBARS, QL, and NO production were significantly increased in PPVL animals. A reduction of SOD activity was found. Glutamine administration markedly alleviated histological abnormalities and oxidative stress, normalized SOD activity, and blocked NO overproduction.Conclusions. Our results confirm that the use of molecules with antioxidant capacity can provide protection of the gastric tissue in portal hypertension. Glutamine treatment can be useful to reduce the oxidative damage induced by PHI on gastric tissue.     

N-acetylcysteine modulates angiogenesis and vasodilation in stomach such as DNA damage in blood of portal hypertensive rats

AIM: To evaluate the antioxidant effect of N-acetylcysteine(NAC) on the stomach of rats with portal hypertension.METHODS: Twenty-four male Wistar rats weighing ± 250 g were divided into four experimental groups(n =6 each): Sham-operated(SO),SO + NAC,partial portal vein ligation(PPVL),and PPVL + NAC. Treatment with NAC in a dose of 10 mg/kg(i.p.) diluted in 0.6 m L of saline solution was administered daily for 7 d starting 8 d after the surgery. Animals from the PPVL and SO group received saline solution(0.6 m L) for the same period of time as the PPVL + NAC and SO + NAC group. On the 15 th day the animals were anesthetized and we evaluated portal pressure by cannulating mesenteric artery. After,we removed the stomach for further analysis. We performed immunohistochemical analysis for endothelial nitric oxide synthase(e NOS),vascular endothelial growth factor(VEGF),and nitrotirosine(NTT) proteins in stomach. We also evaluated e NOS and VEGF by Western blot analysis and assessed DNA damage in blood samples by the comet assay.RESULTS: The portal hypertension group exhibited increases in portal pressure when compared to SO group(29.8 ± 1.8 vs 12.0 ± 0.3 mm Hg)(P 0.001). The same was observed when we compared the e NOS(56.8 ± 3.7 vs 13.46 ± 2.8 pixels)(P 0.001),VEGF(34.9 ± 4.7 vs 17.46 ± 2.6 pixels)(P 0.05),and NTT(39.01 ± 4.0 vs 12.77 ± 2.3 pixels)(P 0.05) expression by immunohistochemistry of the PPVL animals with the SO group. The expression of e NOS(0.39 ± 0.03 vs 0.25 ± 0.03 a.μ)(P 0.01) and VEGF(0.38 ± 0.04 vs 0.26 ± 0.04 a.μ)(P 0.01) were also evaluated by Western blot analysis,and we observed an increase of both proteins on PPVL animals. We also evaluated the DNA damage by comet assay,and observed an increase on damage index and damage frequency on those animals. NAC decreased portal pressure values in PPVL + NAC animals(16.46 ± 2 vs 29.8 ± 1.8 mm Hg)(P 0.001) when compared to PPVL. The expression of e NOS(14.60 ± 4.1 vs 56.8 ± 3.7 pixels)(P 0.001),VEGF(19.53 ± 3.2 vs 34.9 ± 4.7 pixels)(P 0.05) and NTT(21.84 ± 0.7 vs 39.01 ± 4.0 pixels)(P 0.05) evaluated by immunohistochemistry were also reduced in PPVL + NAC animals. Also,when evaluated by Western blot e NOS expression(0.32 ± 0.03 vs 0.39 ± 0.03 a.μ)(P 0.05) and VEGF expression(0.31 ± 0.09 vs 0.38 ± 0.04 a.μ)(P 0.01). Furthermore,NAC modulated DNA damage in PPVL + NAC animals.CONCLUSION: In view of these results,we believe NAC is able to protect the stomach from the alterations induced by the PPVL procedure.     

Antioxidant effect of N-acetylcysteine on prehepatic portal hypertensive gastropathy in rats

Background. Portal hypertension is a clinical syndrome associated with the development of a hyperdynamic circulation and gastroesophageal varices.Aim. To evaluate the antioxidant effect of N-acetylcysteine on portal hypertensive rats.Material and methods. Portal hypertension was induced by partial portal vein ligation (PPVL). Oxidative damage in the stomach was measured by lipoperoxidation trough thiobarbituric acid reactive substances (TBARS) and antioxidant enzyme activity; we also evaluated nitrates and nitrites level and histology stained by hematoxylin-eosin. We performed evaluation of portal pressure and measurement of vessels diameter. Liver damage was evaluated by measuring hepatic enzymes. The animals were divided in four experimental groups (n = 6): Sham-operated (SO), SO + NAC, Partial portal vein ligation (PPVL) and PPVL + NAC. N-acetylcysteine (10 mg/kg ip) was administered daily for 7 days and started 8 days after surgery.Results. The portal hypertensive group showed an increase in portal pressure, vessels diameter, levels of TBARS and nitrates and nitrites when compared to SO group. These values were accompanied by a decrease in superoxide dismutase (SOD) and glutathione peroxidase (GPx) antioxidant enzyme activity. Histology showed dilated vessels in the gastric mucosa in the PPVL group. NAC was able to decrease portal pressure values, vessels diameter, TBARS and also nitrates and nitrites levels when compared to PPVL group. Furthermore, PPVL+NAC group presented an increase in SOD and GPx activity. N-acetylcysteine attenuated damage in gastric mucosa.Conclusion. Oxidative stress is associated with portal hypertension and that antioxidant NAC is able to minimize damages of PPVL in rats.     

Antioxidant role of heme oxygenase-1 in prehepatic portal hypertensive rats

AIM: To study the effect of bilirubin on the oxidative liver status and the activity and expression of heme oxy-genase-1 (HO-1) in rat liver injury induced by prehepatic portal hypertension. METHODS: Wistar male rats, weighing 200-250 g, were divided at random into two groups: one group with prehepatic portal hypertension (PH) induced by regulated prehepatic portal vein ligation (PPVL) and the other group corresponded to sham operated rats. Portal pressure, oxidative stress parameters, antioxidant enzymes, HO-1 activity and expression and hepatic sinusoidal va-sodilatation were measured. RESULTS: In PPVL rats oxidative stress was evidenced by a marked increase in thiobarbituric acid reactive substances (TBARS) content and a decrease in reduced glutathione (GSH) levels. The activities of liver antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were also diminished while activity and expression of HO-1 were enhanced. Administration of bilirubin (5μmol/kg body weight) 24 h before the end of the experiment entirely prevented all these effects. Pretreatment with Sn-pro-toporphyrin IX (Sn-PPIX) (100μg/kg body weight, i.p.), a potent inhibitor of HO, completely abolished the oxidative stress and provoked a slight decrease in liver GSH levels as well as an increase in lipid peroxidation. Besides, carbon monoxide, another heme catabolic product, induced a significant increase in sinusoidal hepatic areas in PPVL group. Pretreatment of PPVL rats with Sn-PPIX totally prevented this effect. CONCLUSION: These results suggest a beneficial role of HO-1 overexpression in prehepatic portal hypertensive rats.     

Increased angiogenesis and permeability in the mesenteric microvasculature of rats with cirrhosis and portal hypertension: an in vivo study.

BACKGROUND: In vivo evidence for angiogenesis in the splanchnic vasodilation in portal hypertension (PHT) and cirrhosis is lacking. Vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) are mediators of angiogenesis. The present study visualises in vivo structural changes (angiogenesis and vascular hyperpermeability) and examines the presence of VEGF and eNOS in the mesenteric microvasculature of animal models of PHT with and without cirrhosis. METHODS: Portal hypertension was induced by partial portal vein ligation (PPVL) and cirrhosis was induced by common bile duct ligation (CBDL) in rats. The mesenteric microcirculation was examined by intravital microscopy. Expression of VEGF, eNOS and CD31 in mesenteric tissue were studied by immunohistochemistry. RESULTS: An increased mesenteric angiogenesis was observed in PPVL and CBDL rats compared with Sham-operated and control rats, as shown by intravital microscopy and CD 31 staining. VEGF and eNOS expression was higher in CBDL and PPVL rats compared with control groups and correlated positively with vascular density. Macromolecular leakage was increased in cirrhotic rats compared with control and PPVL rats. CONCLUSION: Our study provides in vivo evidence of an increased angiogenesis in the mesenteric microvasculature of animal models of PHT and cirrhosis. Increased VEGF and eNOS expression in the mesentery of PPVL and CBDL rats may suggest their contribution. Microvascular permeability in the mesenteric vessels was only increased in cirrhotic rats.     

Role of shear stress in aortic eNOS up-regulation in rats with biliary cirrhosis

BACKGROUND & AIMS: In rats with portal vein stenosis, the initial cause of aortic nitric oxide (NO) overproduction might be overactivation of endothelial NO synthase (eNOS) related to increased shear stress. Cardiac output is higher in cirrhosis than in extrahepatic portal hypertension. The aims of this study were to evaluate the role of shear stress, vascular endothelial growth factor (VEGF), and cytokines in aortic eNOS up-regulation in rats with biliary cirrhosis and to compare these results with those in rats with portal vein stenosis. METHODS: NOS activities, NOS protein, heat shock protein (Hsp) 90, and VEGF expressions were studied in rat aortas. Propranolol was administered to rats with cirrhosis to reduce cardiac output and thus shear stress. RESULTS: In cirrhotic rats, the aortic eNOS protein was 3.0 and 1.7 times higher than in control and portal vein-stenosed rats, respectively. In cirrhotic rats, the Hsp90 content was 3.2 and 2.2 times higher than in control and portal vein-stenosed rats, respectively. Propranolol decreased NOS activity by 47% and eNOS and Hsp90 expression by 75% and 72%, respectively. Aortic VEGF expression was decreased in cirrhotic rats. VEGF-induced stimulation of NOS activity was greater in aortas from control rats than in aortas from portal vein-stenosed or cirrhotic rat aortas. eNOS expression was up-regulated after VEGF incubation. After lipopolysaccharide administration, eNOS expression did not change in portal vein-stenosed or cirrhotic rats. CONCLUSIONS: This study shows that in aortas from rats with biliary cirrhosis, systemic vasodilation depends mainly on eNOS up-regulation related to shear stress.     

Caloric restriction improves endothelial dysfunction during vascular aging: Effects on nitric oxide synthase isoforms and oxidative stress in rat aorta

Aging is characterized by activation of inducible over endothelial nitric oxide synthase (iNOS and eNOS), impaired antioxidant activity and increased oxidative stress, which reduces nitric oxide bioavailability and causes endothelial dysfunction. Caloric restriction (CR) blunts oxidative stress. We investigated whether CR impacts endothelial dysfunction in aging and the underlying mechanisms. Aortas from young (YC, 6 months of age) and old (OC, 24 months of age) rats ad-libitum fed and from old rats caloric-restricted for 3-weeks (OR, 26%) were investigated. Endothelium-dependent vasorelaxation was impaired in OC, associated with reduced eNOS and increased iNOS expression (P < 0.05). Aortic nitrite was similar in OC and YC, but the contribution of calcium-independent NOS to total NOS activity was increased whereas that of calcium-dependent NOS was reduced (p ≤ 0.0003). Plasma thiobarbituric acid-reactive substances (TBARS) were elevated in OC as well as aortic nitrotyrosine (P < 0.05). Expression of manganese superoxide dismutase (MnSOD) and total SOD activity were impaired in OC (P < 0.05 vs. YC), whereas copper-zinc (CuZn) SOD expression was similar in OC and YC. CR restored endothelial dysfunction in old rats, reduced iNOS expression, total nitrite and calcium-independent NOS activity in aorta (P < 0.05) without changes in eNOS expression and calcium-dependent NOS activity. Sirtuin-1 expression did not differ among groups. Plasma TBARS and aortic nitrotyrosine were reduced (P < 0.05) in OR compared with OC. In OR CuZnSOD protein and SOD activity increased (P < 0.05) without changes in MnSOD expression. Short-term CR improves age-related endothelial dysfunction. Reversal of altered iNOS/eNOS ratio, reduced oxidative stress and increased SOD enzyme activity rather than enhanced NO production appear to be involved in this effect.     

肝前性门静脉高压大鼠NO、CO与高动力循环的关系

目的 观察肝前性门静脉高压大鼠血中一氧化氮（NO）、碳氧血红蛋白（COHb)与血液循环动力指标的关系。方法 制作门静脉高压大鼠模型和假手术组模型。分别检测血中NO、COHb浓度，测定门静脉压力。血流和平均动脉压。结果 门静脉高压组大鼠血中NO、COHb浓度均较假手术组高，门静脉高压组大鼠门静脉压增高，门静脉血流减少及平均动脉压降低，血中NO、CO-Hb水平分别与门静脉压力呈正相关，与门静脉血流和平均动脉压呈负相关。结论 NO、一氧化碳（CO）的过度形成和释放对门静脉高压的形成和维持起重要作用。     

Association between oxidative stress and vascular reactivity in children with sickle cell anaemia and sickle haemoglobin C disease

Oxidative stress and haemolysis‐associated nitric oxide (NO) depletion plays a crucial role in the development of vasculopathy in sickle cell anaemia (SS). However it remains unknown whether oxidative stress and haemolysis levels influence vascular function in patients with sickle haemoglobin C disease (SC). Microvascular response to heat (using Laser Doppler flowmetry on finger), oxidative stress biomarkers, NO metabolites, endothelin‐1 and haematological parameters were compared between patients with SS and SC. Vascular function, oxidative and nitrosative markers were also measured in healthy (AA) children. SS and SC had increased plasma advanced oxidation protein products (AOPP), malondialdehyde, plasma antioxidant activities and NO end products, compared to AA. SC had lower catalase activity compared to AA and SS. Haemolytic rate, glutathione peroxidase and nitrotyrosine concentrations were significantly increased in children with SS compared to SC and AA. SS and SC had impaired microvascular reactivity compared to AA. In SS, the plateau phase of the response to local thermal heating was negatively associated with nitrotyrosine and AOPP. No association between vascular function parameters and oxidative stress markers was observed in SC. Mild haemolysis in SC, compared to SS, may limit oxidative and nitrosative stress and could explain the better preserved microvascular function in this group.     

Exercise restores endothelial function independently of weight loss or hyperglycaemic status in <Emphasis Type="Italic">db/db</Emphasis> mice

AIMS/HYPOTHESIS: Exercise ameliorates oxidative stress-mediated diabetic vascular endothelial dysfunction through poorly defined mechanisms. We hypothesised that, in addition to improving metabolic parameters, upregulation of antioxidants such as superoxide dismutase (SOD) mediates exercise-induced reductions of oxidative stress and increased nitric oxide (NO) bioavailability, and also restores vasodilatation. METHODS: Type 2 diabetic db/db and normoglycaemic wild-type mice were exercised at moderate intensity for 1 h a day for 7 weeks, leading to a 10% body weight loss. Sedentary animals or those undergoing a low-intensity exercise regimen causing non-significant weight loss were also used. We examined aortic endothelial cell function, NO bioavailability and various biomarkers of oxidative stress. RESULTS: Moderate-intensity exercise lowered body weight, increased mitochondrial manganese SOD (MnSOD) and both total and phosphorylated (Ser1177) endothelial nitric oxide synthase (eNOS) protein production; it also reduced whole-body (plasma 8-isoprostane) and tissue oxidative stress (nitrotyrosine immunostaining or protein carbonyl levels in the aorta). Low-intensity exercise did not alter body weight; however, it upregulated cytosolic Cu/Zn-SOD instead of MnSOD, and still demonstrated all the above benefits in the db/db aorta. Importantly, both exercise protocols improved endothelial-dependent vasodilatation and NO bioavailability without altering hyperglycaemic status in db/db mice. CONCLUSIONS/INTERPRETATION: Exercise reverses diabetic vascular endothelial dysfunction independently of improvements in body weight or hyperglycaemia. Our data suggest that upregulation of eNOS and specific SOD isoforms could play important roles in improving NO bioavailability, as well as in reversing endothelial dysfunction in type 2 diabetes patients through lifestyle modifications in the management of diabetes.     

氯吡格雷对尼古丁诱导的血管内皮损伤的保护作用

目的探讨尼古丁对血管内皮细胞的影响及氯吡格雷的保护作用。方法将40只SD大鼠分为5组,对照组、模型组(尼古丁2 mg/kg)、尼古丁损伤+氯吡格雷低剂量组(低剂量组)、尼古丁损伤+氯吡格雷中剂量组(中剂量组)、尼古丁损伤+氯吡格雷高剂量组(高剂量组),每组8只。尼古丁造模4周后,测定大鼠血浆超氧化物歧化酶(SOD)、内皮素1、NO及内皮型一氧化氮合酶(eNOS)浓度,免疫组织化学法及Western blot法测定血管eNOS阳性细胞的表达。结果与对照组比较,模型组大鼠血浆NO、eNOS及SOD浓度明显下降,而内皮素1浓度明显上调,eNOS阳性细胞表达明显减少(P0.01);与模型组比较,低、中、高剂量组大鼠NO、eNOS及SOD浓度明显升高,eNOS阳性细胞表达明显增多,且中、高剂量组大鼠增多更显著(P0.05,P0.01)。结论氯吡格雷可能抑制氧化应激反应,调节内皮细胞中eNOS的正常表达,从而缓解尼古丁对血管内皮细胞的损害。     

Primary role of superoxide anion generation in the cascade of events leading to endothelial dysfunction and damage in high glucose treated HUVEC

AimThe aim of the study was to elucidate the chain of events leading to oxidative damage in endothelial cells exposed to high glucose.MethodThe nitric oxide synthase (NOS) cofactor tetrahydrobiopterin (BH₄), the peroxynitrite decomposition catalyst FP15, the inhibitor of mitochondrial complex II thenoyltrifluoroacetone (TTFA) and the antioxidant superoxide dismutase (SOD) mimetic Mn(III)tetrakis(4-benzoic acid) porphyrin chloride (MnTBAP) were individually added to human umbilical vein endothelial cells (HUVEC) cultured in high glucose. This study was designed to establish the possible sequence of action of NOS, peroxynitrite and superoxide anion in the oxidative damage cascade.ResultsWe found that in high glucose, nitrotyrosine, 8OHdG, NO (+40%) and O₂⁻ (+300%) production, eNOS and caspase-3 expression increased, while Bcl-2 expression decreased. MnTBAP and TTFA were able to normalize all the parameters assayed. FP15 caused an increase in NO production, did not interfere with eNOS expression and O₂⁻ generation, but was able to reduce apoptosis and to normalize nitrotyrosine and 8OHdG formation. BH₄ enrichment was able to reduce O₂⁻ generation, nitrotyrosine and 8OHdG formation and apoptosis. The addition of this cofactor did not affect eNOS expression, but increased NO formation, more than FP15.ConclusionThese data show the starting role of superoxide anion generated at mitochondrial level in the cascade of events leading to hyperglycemia generated apoptosis.     

Reduced oxidative and nitrosative damage in murine experimental colitis in the absence of inducible nitric oxide synthase

BACKGROUND: Oxidative and nitrosative stress have been implicated in the pathogenesis of inflammatory bowel diseases. AIMS: To study the role of nitric oxide (NO) derived from inducible NO synthase (iNOS) in an experimental model of murine enterocolitis. METHODS: Trinitrobenzene sulphonic acid (TNBS) was instilled per rectum to induce a lethal colitis in iNOS deficient mice and in wild type controls. The distal colon was evaluated for histological evidence of inflammation, iNOS expression and activity, tyrosine nitration and malondialdehyde formation (as indexes of nitrosative and oxidative stress), myeloperoxidase activity (as index of neutrophil infiltration), and tissue localisation of intercellular adhesion molecule 1 (ICAM-1). RESULTS: TNBS administration induced a high mortality and weight loss associated with a severe colonic mucosal erosion and ulceration, increased myeloperoxidase activity, increased concentrations of malondialdehyde, and an intense staining for nitrotyrosine and ICAM-1 in wild type mice. Genetic ablation of iNOS gene conferred to mice a significant resistance to TNBS induced lethality and colonic damage, and notably reduced nitrotyrosine formation and concentrations of malondialdehyde; it did not, however, affect neutrophil infiltration and intestinal ICAM-1 expression in the injured tissue. CONCLUSION: Data show that activation of iNOS is required for nitrosative and oxidative damage in experimental colitis.     

Lack of inducible NO synthase reduces oxidative stress and enhances cardiac response to isoproterenol in mice with deoxycorticosterone acetate-salt hypertension

Although NO derived from endothelial NO synthase (eNOS) is thought to be cardioprotective, the role of inducible NO synthase (iNOS) remains controversial. Using mice lacking iNOS (iNOS-/-), we studied (1) whether development of hypertension, cardiac hypertrophy, and dysfunction after deoxycorticosterone acetate (DOCA)-salt would be less severe compared with wild-type controls (WT; C57BL/6J), and (2) whether the cardioprotection attributable to lack of iNOS is mediated by reduced oxidative stress. Mice were uninephrectomized and received either DOCA-salt (30 mg/mouse SC and 1% NaCl+0.2% KCl in drinking water) or vehicle (tap water) for 12 weeks. Systolic blood pressure (SBP) was measured weekly. Left ventricular (LV) ejection fraction (EF) by echocardiography and cardiac response to isoproterenol (50 ng/mouse IV) were studied at the end of the experiment. Expression of eNOS and iNOS as well as the oxidative stress markers 4-hydroxy-2-nonenal (4-HNE, a marker of lipid peroxidation) and nitrotyrosine (a marker for peroxynitrite) were determined by Western blot and immunohistochemical staining, respectively. DOCA-salt increased SBP and LV weight similarly in both strains and decreased EF in WT but not in iNOS-/-. Cardiac contractile and relaxation responses to isoproterenol were greater, 4-HNE and nitrotyrosine levels were lower, and eNOS expression tended to be higher in iNOS-/-. We conclude that lack of iNOS leads to better preservation of cardiac function, which may be mediated by reduced oxidative stress and increased eNOS; however, it does not seem to play a significant role in preventing DOCA-salt-induced hypertension and hypertrophy.     

Supplementation with tetrahydrobiopterin prevents the cardiovascular effects of angiotensin II-induced oxidative and nitrosative stress

OBJECTIVE: The pteridine cofactor tetrahydrobiopterin (BH4) has emerged as a critical determinant of endothelial nitric oxide synthase (eNOS) activity. When BH4 availability is limited, eNOS does not produce nitric oxide (NO) but instead generates superoxide. BH4 may reverse endothelial dysfunction due to cardiovascular disease, including atherosclerosis, coronary artery disease and hypertension. In this study, the influence of BH4 on cardiovascular parameters and the production of free radicals following angiotensin II (Ang II) infusion was assessed. METHODS: BH4 (20 mg/kg per day in drinking water) was administered with Ang II (300 ng/kg per min subcutaneously, osmotic pump) for 7 days in Sprague-Dawley rats. In addition, BH4 was also given in vehicle-infused rats. RESULTS: Treatment with BH4 significantly prevented some of the effects of Ang II, such as impaired vascular responses to acetylcholine, hypertension and increases in heart weight index values. Treatment with BH4 also significantly reduced Ang II-induced increases in inducible NO synthase expression, nitrotyrosine immunostaining, NO production and superoxide anion formation in rats. CONCLUSION: These results indicate that BH4 might prevent the development of hypertension and myocardial hypertrophy, as well as the Ang II-induced production of superoxide and NO, thereby reducing the production of peroxynitrite. Therefore, BH4 may protect against the cardiovascular manifestations of oxidative and nitrosative stress in this experimental model of Ang II-mediated hypertension.     

Vascular hyporesponsiveness in the mesenteric artery of anaesthetized rats with cirrhosis and portal hypertension: an in-vivo study

INTRODUCTION: Cirrhosis is complicated by splanchnic vasodilation. Nitric oxide (NO) and prostacyclin contribute to this. Vascular hyporesponsiveness has been reported, but the underlying pathophysiological mechanisms are unclear. OBJECTIVE: This in-vivo study examined the contribution of NO and prostacyclin to the development of vascular hyporesponsiveness in the mesenteric circulation of animals with cirrhosis and portal hypertension. METHODS: Rats underwent common bile duct ligation (CBDL) (n = 11), partial portal vein ligation (PPVL) (n = 12) and sham-operation (sham) (n = 11). Blood flow in the mesenteric artery (MBF) was measured during intramesenteric infusion of endothelium-dependent (acetylcholine) and endothelium-independent vasodilators (deta-NONOate, pinacidil) and a vasoconstrictor (L-phenylephrine). The measurements were repeated after systemic infusion of L-NAME (NO synthase inhibition) and indomethacin (cyclo-oxygenase inhibition). RESULTS: The MBF response to acetylcholine was significantly lower in CBDL and tended to be lower in PPVL than in sham. L-NAME and indomethacin significantly decreased the MBF response to acetylcholine in all groups. The hyporeactivity to acetylcholine in CBDL and PPVL was maintained after L-NAME and indomethacin. The MBF response to pinacidil, deta-NONOate and phenylephrine, before and after NO synthase and cyclo-oxygenase inhibition, was lower in CBDL and PPVL than in sham. CONCLUSION: This is the first in-vivo study demonstrating an impaired response to endothelium-dependent and endothelium-independent vasodilators as well as vasoconstrictors in the mesenteric artery of animals with cirrhosis and portal hypertension. The generalised hyporeactivity suggests an abnormality on the vascular smooth muscle cell level. The hyporesponsiveness persisted after combined NO synthase and cyclo-oxygenase inhibition.     

Estrogen improves the hyperdynamic circulation and hyporeactivity of mesenteric arteries by alleviating oxidative stress in partial portal vein ligated rats

AIM:To evaluate the effects of estrogen(E2) on systemic and splanchnic hyperdynamic circulation in portal hypertensive rats.METHODS:Fifty castrated female Sprague-Dawley rats were divided into five groups:sham operation(SO),partial portal vein ligation(PPVL) + placebo(PLAC),PPVL + E2,PPVL + ICI and PPVL + E2 + ICI. Hemodynamic measurements were performed using ultrasonography. Mesenteric arteriole contractility in response to norepinephrine was determined using a vessel perfusion system. Oxidative stress in the mesenteric artery was investigated by in situ detection of the superoxide anion(O2) and hydrogen peroxide(H2O2) concentrations.RESULTS:Treatment with E2 resulted in a significant decrease of portal pressure(P < 0.01) and portal venous inflow(P < 0.05),and higher systemic vascular resistance(P < 0.05) and splanchnic arteriolar resistance(P < 0.01) in PPVL + E2 rats compared to PPVL+ PLAC rats. In the mesenteric arterioles of PPVL +E2 rats,the dose-response curve was shifted left,and the EC50was decreased(P < 0.01). E2 reduced O2 production and H2O2concentration in the mesenteric artery. However,ICI182,780 reversed the beneficial effects of E2,therefore,the systemic and splanchnic hyperdynamic circulation were more deteriorated in ICI182,780-treated rats.CONCLUSION:Treatment with estrogen improved the systemic and splanchnic hyperdynamic circulation in PPVL rats,in part due to the alleviation of oxidative stress.     

The role of portal pressure in the severity of bleeding in portal hypertensive rats

The aim of this study was to investigate the role of portal hypertension determining the severity of bleeding in portal hypertensive rats. The effects of section of branches of the ileocolic vein were studied in sham-operated (SO), partial portal vein-ligated (PPVL), and common bile duct-ligated (CBDL) rats. The ensuing hemorrhage was compared with that caused by section of femoral vein, where the portal hypertensive factor is excluded. In PPVL rats, section of branches of increasing size (divided into fourth, third, second, and first order) resulted in increasingly severe bleeding (arterial pressure: / +/- 4%, / 6 +/- 12%, / /15 +/- 8%, and / 28 +/- 13%; P <.005; hematocrit / 4 +/- 2%, / 6 +/- 1%, / 7 +/- 2%, and / 10 +/- 4%; P <.005). Bleeding from first-order branches was mild in SO, moderate in PPVL, and severe in CBDL rats, as shown by increasing changes in arterial pressure (/ 3 +/- 3%, / 12 +/- 16% and, / 43 +/- 23%; P <.01), hematocrit (/ 4 +/- 1%, / 12 +/- 2%, and / 32 +/- 19%; P <.01), and mortality (0%, 0%, and 56%; P <.001). Greater blood loss in CBDL rats was associated with higher portal pressure (16.6 +/- 2.7 vs. 13. 1 +/- 1.1 mm Hg in PPVL; P <.01) and more prolonged bleeding time (70 +/- 4 vs. 35 +/- 3 seconds in PPVL; P <.001). Vessels were similarly dilated in CBDL and PPVL (0.7 +/- 0.2 and 0.7 +/- 0.1 vs. 0.4 +/- 0.1 mm in SO; P <.05). Section of femoral vein caused equal blood loss in SO, PPVL, and CBDL rats, assessed by falls in hematocrit (/ 8 +/- 2%, / 7 +/- 1%, / 8 +/- 1%, respectively; NS) and by the blood loss (3.6 +/- 0.7, 3.5 +/- 0.9, and 3.8 +/- 0.7 g; NS). The study shows that the degree of portal pressure elevation is a major determinant of the severity of portal hypertension-related bleeding in PPVL and CBDL rats.