Plasma D (-)-lactate as a new marker for diagnosis of acute intestinal injury following ischemia-reperfusion

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Tempol prevents harmful effects of remote ischemia reperfusion injury on healing of experimental colonic anastomoses

Background and aims Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) is a water-soluble analogue of the spin label TEMPO. As an antioxidative agent, it is a member of nitroxides, which detoxifies superoxide and possibly other toxic radicals in vivo. In this study, we aimed to investigate whether tempol prevents harmful systemic effects of superior mesenteric ischemia-reperfusion on left colonic anastomosis in rats. Materials and methods Anastomosis of the left colon was performed in 30 rats that were divided into three groups each having ten animals: sham-operated control (group I), 60 min of intestinal ischemia-reperfusion by superior mesenteric artery occlusion (group II), and tempol-treated group (30 mg/kg before and after the ischemia-reperfusion (group III). On postoperative day 5, all animals were killed and anastomotic bursting pressures were measured in vivo. Tissue samples were obtained for further investigation of anastomotic hydroxyproline content, perianastomotic malondialdehyde, and glutathione levels. Results There was a statistically significant increase in the quantity of myeloperoxidase activity and malondialdehyde levels in group II, along with a decrease in glutathione levels, anastomotic hydroxyproline content, and bursting pressure values when compared to controls. However, all of the investigated parameters were normalized in tempol-treated animals (group III). Conclusion We conclude that tempol significantly prevents harmful systemic effects of reperfusion injury on colonic anastomoses in a rat model of superior mesenteric artery occlusion.     

Differential expression of pulmonary nitric oxide synthase isoforms after intestinal ischemia-reperfusion

BACKGROUND/AIMS: Nitric oxide has been implicated in both attenuating and aggravating ischemia-reperfusion injury in most organs. This study aimed to investigate the role of nitric oxide produced by the two principal isoforms of nitric oxide synthase in the lung during post-ischemic reperfusion of the intestine. METHODOLOGY: Rats were randomized into four groups of 6 animals: Group A: laparotomy and superior mesenteric artery dissection without occlusion and maintenance for 2 h (control group at 2 h). Group B: laparatomy and superior mesenteric artery occlusion for 30 min and reperfusion of the intestine for 2 h (ischemia-reperfusion group at 2 h). Group C: control animals at 6 h. Group D: ischemia-reperfusion animals at 6 h. Arterial blood pressure was monitored throughout the procedure. Animals were euthanazed at the end of the experiment, and lungs were harvested for histological assessment of injury and for immunohistochemical examination of nitric oxide synthase isoforms and nitrotyrosine. RESULTS: In all animals subjected to intestinal ischemia a period of systemic hypotension occurred immediately upon reperfusion. Histological evidence of lung injury was limited to those animals subjected to an intestinal reperfusion insult. Compared to control animals, pulmonary endothelial nitric oxide synthase expression was diminished at 2 h (p = 0.002), while expression of inducible nitric oxide synthase (p = 0.002) and nitrotyrosine (p = 0.02) was increased at 6 h. CONCLUSIONS: Following intestinal ischemia-reperfusion, early pulmonary damage is associated with decreased endothelial nitric oxide synthase expression in the lung. Expression of inducible nitric oxide synthase occurs during the later stages of reperfusion; this leads to overproduction of nitric oxide with consequent nitrosylation of protein tyrosine residues and thus aggravated pulmonary injury.     

Doppler US of superior mesenteric artery in the assessment of ulcerative colitis. A prospective study

BACKGROUND/AIMS: The purpose of this study was to correlate blood flow velocity in the superior mesenteric artery and activity of ulcerative colitis. METHODOLOGY: Doppler spectral analysis of superior mesenteric artery blood flow velocities were obtained in a blind study from 28 patients after fasting (A1: 13 patients with pancolitis, A2: 5 patients with subtotal colitis, B: 10 patients with left-sided colitis) and 50 healthy volunteers (control group). Disease activity was determined with clinical and endoscopic findings. RESULTS: A significant increase in superior mesenteric artery blood flow measurements was observed in the active pancolitis group A1 [Vsyst = 3.64 +/- 0.18 m/sec and Vdiast = 0.94 +/- 0.09 m/sec as compared with healthy volunteers (Vsyst = 1.14 +/- 0.07 m/sec, Vdiast = 0.38 +/- 0.04 m/sec) P < 0.01. A minor increase in superior mesenteric artery blood flow velocity was observed in patients with subtotal colitis, group A2 (Vsyst = 2.06 +/- 0.14 m/sec, Vdiast = 0.45 +/- 0.05 m/sec) as compared with healthy volunteers P < 0.01. In group B with left sided colitis superior mesenteric artery velocity changes were not statistically significant (P > 0.05). CONCLUSIONS: Doppler US velocity measurement of superior mesenteric artery may be used as an adjunct in the assessment of ulcerative colitis extension and activity.     

Changes in lipopolysaccharide concentrations in hepatic portal and systemic arterial plasma during intestinal ischemia in monkeys

The time course of changes in the level of plasma lipopolysaccharides (LPS) in both the hepatic portal and the systemic arterial circulations, together with changes in cardiovascular parameters, was ascertained during a 1 hr occlusion of the superior mesenteric artery (SMA) in six primates. The LPS concentrations before occlusion of the SMA in the hepatic portal and systemic arterial circulation were 0.051 +/- 0.009 and 0.065 +/- 0.011 ng/ml, respectively (NS). At the end of the occlusion period, there was no significant increase in either the hepatic portal or systemic arterial plasma LPS concentrations. Immediately on removal of the occlusion, however, the LPS concentration in the portal plasma increased and peaked at 0.431 +/- 0.124 ng/ml (P less than 0.01) within 17.5 +/- 1.71 min, whereas in the systemic arterial circulation the LPS concentration began to rise but only after a delay of approximately 10 min to peak at 0.287 +/- 0.126 ng/ml (P less than 0.05) within 32.5 +/- 4.23 min of reperfusion. The mean arterial pressure (MAP) declined during the reperfusion period from 98.6 +/- 6.89 to 65.0 +/- 9.5 mm Hg (P less than 0.05). The heart rate showed a small but not significant increase (P greater than 0.2) after about 80 min of reperfusion. These data indicate that the gut is the source of the increased plasma LPS concentration following occlusion of the SMA.     

Studies on intragastric PCO2 at rest and during exercise as a marker of intestinal perfusion in patients with chronic heart failure

AIMS: The aim of this study was to investigate mesenteric ischaemia by determining intragastric PCO(2) (iPCO(2)) with gastric tonometry during rest and exercise stress testing in patients with chronic heart failure (CHF). In CHF inflammatory immune activation is hypothesized to result from a chronic endotoxin challenge due to bacterial translocation of hypoperfused intestinal mucosa. METHODS AND RESULTS: In 10 patients with CHF and ten healthy controls a tonometry catheter was inserted into the stomach. IPCO(2) was measured at rest and during bicycle exercise every 5 min. At rest arterial pCO(2) (aPCO(2)), intragastric pCO(2) (iPCO(2)) and the intragastric/arterial gap did not differ between patients and controls. During low level exercise (25 W), patients showed an increase in iPCO(2) compared to resting iPCO(2), whereas controls did not show an increase in iPCO(2) (change in iPCO(2): 12+/-2% vs. 1+/-0.4%, P<0.001). In CHF, iPCO(2) during peak exercise was 25+/-3% higher than at rest, compared to controls (increase 2+/-1, P<0.0001). CONCLUSIONS: Patients with CHF already at low level exercise develop an increase in iPCO(2). This is likely to reflect hypoperfusion of the intestinal mucosa, which may contribute to the development of bacterial translocation.     

鲜生地汁对大鼠肠缺血再灌注损伤的防护作用

目的:探讨鲜生地汁对大鼠肠缺血再灌注损伤(I/R)的防护作用及其机制。方法:采用肠系膜上动脉(SMA)夹闭方法制作I/R模型。实验大鼠随机分为正常组、I/R模型组、I/R 鲜生地汁大剂量组、I/R 鲜生地汁小剂量组、I/R 乳果糖组。观察肠系膜上动脉夹闭0.5小时再灌注24小时、48小时、72小时后肠黏膜损伤程度,测定血浆内毒素水平。结果:各时点I/R 鲜生地汁大剂量、I/R 小剂量组及I/R 乳果糖组肠黏膜损伤程度、血浆内毒素水平均低于I/R模型组(P<0.05)。结论:鲜生地汁对肠缺血再灌注损伤大鼠肠黏膜具有保护作用。     

TNF-α and plasma D(-)-lactate levels in rats after intestinal ischemia and reperfusion

Objective To study the potential role of tumor necrosis factor-α (TNF-α) induction in the development of mucosal barrier dysfunction in rats caused by acute intestinal ischemia-reperfusion injury, and to examine whether pretreatment with monoclonal antibody against TNF-α (TNF-α MoAb) would affect the release of D(-)-lactate after local gut ischemia followed by reperfusion. Methods Anesthetized Sprague-Dawley rats underwent superior mesenteric artery occlusion for 75 min followed by reperfusion for 6 hr. The rats were treated intravenously with either TNF-α MoAb (20 mg/kg) or albumin (20 mg/kg) 30 min prior to the onset of ischemia. Plasma D(-)-lactate levels were measured in both the portal and systemic blood by an enzymatic spectrophotometric assay. Intestinal TNF-αmRNA expression as well as protein levels were also measured at various intervals. In addition, a postmortem examination was performed together with a macropathological evaluation based on a four-grade scoring system.Results Intestinal ischemia resulted in a significant elevation in D(-)-lactate levels in the portal vein blood in both the control and treatment groups ( P ＜0.05). However, animals pretreated with TNF-α MoAb at 6 hr after reperfusion showed significant attenuation of an increase in both portal and systemic D(-)-lactate levels when compared with those only receiving albumin (P ＜ 0.05). In the control animals, a remarkable rise in intestinal TNF-α level was measured at 0.5 hr after clamp release ( P ＜ 0.01); however, prophylactic treatment with TNF-α MoAb completely annulled the increase of local TNF-α levels seen in the control animals. Similarly, after anti-TNF-α MoAb administration, intestinal TNF-α mRNA expression was markedly inhibited, which showed significant differences when compared with the control group at 0.5 hr, 2 hr and 6 hr after the release of occlusion ( P ＜ 0.05-0.01 ). In addition, the pathological examination showed marked intestinal lesions that formed during ischemia, which were much worse upon reperfusion,particularly at the 6 hr time point. These acute injuries were obviously attenuated in animals receiving TNF-α MoAb.Conclusions It appeared that acute intestinal ischemia was associated with failure of the mucosal barrier, resulting in increased plasma D(-)-lactate levels in both portal and systemic blood. These results suggest that TNF-α appears to be involved in the development of local damage associated with intestinal ischemic injury. Moreover, prophylactic treatment with TNF-α MoAb exerts preventive effects on ischemia/ reperfusion-induced circulating D (-)-lactate elevation and gut injury. ( J Geriatr Cardiol 2004;1(2):119-124. )     

Superior mesenteric artery is more important than inferior mesenteric artery in maintaining colonic mucosal perfusion and integrity in rats

Mucosal hemodynamics (by reflectance spectrophotometry) and mucosal damage (by histologic examination) following acute colonic ischemia were evaluated in different anatomic locations in the colon of anesthetized rats. The reflectance spectrophotometer provides an index of mucosal hemoglobin concentration (IHB) and an index of oxygen saturation of hemoglobin (ISO₂). The patterns of ischemia without congestion (IHB, ISO₂) during superior mesenteric artery occlusion, and ischemia with congestion (IHB, ISO₂) during portal vein occlusion, previously demonstrated in the stomach and duodenum, are also applicable to the colon. The significant linear correlations between changes (as percent of baseline) in IHB, ISO₂, and hydrogen gas clearance suggest that changes in these indices are adequate indicators of changes in colonic mucosal perfusion. Superior mesenteric artery ligation produced significant reductions in both indices, and an increase in damage in the mucosa of the cecum, transverse colon, splenic flexure, and left colon, but not the rectum. Inferior mesenteric artery ligation produced only slight reduction in these indices and minimal damage only in the mucosa of the splenic flexure. These results support the hypothesis that the superior mesenteric artery is more important than the inferior mesenteric artery in maintaining colonic perfusion and colonic mucosal integrity in the rat.Supported by the American Society for Gastrointestinal Endoscopy Career Development Award (H850208, H870212), Veterans Administration Medical Research Funds; and in part by research grants (0162-01, 0162-02; 0291-01) from the Smokeless Tobacco Research Council, Inc.; and by funds provided by the Cigarette and Tobacco Surtax Fund of the State of California through the Tobacco Related Disease Research Program of the University of California.     

TNF-α and plasma D(-)-lactate levels in rats after intestinal ischemia and reperfusion

Objective To study the potential role of tumor necrosis factor-or(TNF-α)induction in the development ofmucosal barrier dysfunction in rats caused by acute intestinal ischemia-reperfusion injury,and to examine whetherpretreatment with monoclonal antibody against TNF-α(TNF-αMoAb)would affect the release of D(-)-lactate afterlocal gut ischemia followed by reperfusion.Methods Anesthetized Sprague-Dawley rats underwent superiormesenteric artery occlusion for 75 min followed by reperfusion for 6 hr.The rats were treated intravenonsly with eitherTNF-α MoAb(20 mg/kg)or albumin(20 mg/kg)30 min prior to the onset of ischemia.Plasma D(-)-lactate levelswere measured in both the portal and systemic blood by an enzymatic spectrophotometrie assay.Intestinal TNF-αmRNA expression as well as protein levels were also measured at various intervals.In addition,a postmortemexamination was performed together with a macropatholngical evaluation based on a four-grade scoring system.Results Intestinal ischemia resulted in a significant elevation in D(-)-lactate levels in the portal vein blood in boththe control and treatment groups(P<0.05).However,animals pretreated with TNF-α MoAb at 6 hr after reperfusionshowed significant attenuation of an increase in both portal and systemic D(-)-lactate levels when compared with thoseonly receiving albumin(P<0.05).In the control animals,a remarkable rise in intestinal TNF-α level was measuredat 0.5 hr after clamp release(P<0.01);however,prophylactic treatment with TNF-α MoAb completely annulled theincrease of local TNF-α levels seen in the control animals.Similarly,after anti-TNF-α MoAb administration,intestinalTNF-α mRNA expression was markedly inhibited,which showed significant differences when compared with the controlgroup at 0.5 hr,2 hr and 6 hr after the release of occlusion(P<0.05-0.01).In addition,the pathologicalexamination showed marked intestinal lesions that formed during ischemia,which were much worse upon reperfusion,particularly at the 6 hr time point.These acute injuries were obviously attenuated in animals receiving TNF-α MoAb.Conclusions It appeared that acute intestinal ischemia was associated with failure of the mucosal barrier,resulting inincreased plasma D(-)-lactate levels in both portal and systemic blood.These results suggest that TNF-α appears to beinvolved in the development of local damage associated with intestinal ischemic injury.Moreover,prophylactictreatment with TNF-α MoAb exerts preventive effects on ischemia/reperfusion-induced circulating D(-)-lactateelevation and gut injury.(J Geriatr Cardiol 2004;1(2):119-124.)     

Dietary Glutamine Supplementation Prevents Mucosal Injury and Modulates Intestinal Epithelial Restitution Following Ischemia-Reperfusion Injury in the Rat

The aim of the present study was to evaluate the preventive effect of a 2-day oral glutamine supplementation against intestinal ischemia-reperfusion (IR) injury in a rat. Male Sprague-Dawley rats were divided into four experimental groups: sham rats underwent laparotomy, sham-GLU rats underwent laparotomy and were treaded with enteral glutamine (GLU) given in drinking water (2%) 48 hr before and following operation, IR rats underwent occlusion of both the superior mesenteric artery and the portal vein for 30 min followed by 24 hr of reperfusion, and IR-GLU rats were treated with enteral glutamine 48 hr before and following IR. Intestinal mucosal damage (Park’s injury score), mucosal structural changes, enterocyte proliferation, and enterocyte apoptosis were determined 24 hr following IR. Sham-GLU rats demonstrated a lower rate of cell apoptosis in jejunum and ileum compared to sham animals. IR-GLU animals demonstrated a greater jejunal and ileal bowel and mucosal weight, mucosal DNA, villous height and crypt depth, and enterocyte proliferation index in ileum and a lower injury score grade in jejunum compared to IR-nontreated rats. In conclusion, pretreatment with oral glutamine prevents mucosal injury and improves intestinal recovery following IR injury in the rat.     

The effects of anisodamine and dobutamine on gur mucosal blood flow during gut ischemia／reperfusion

AIM：To detemine if anisodamine is able to augment mucsal perfusion during gut I/R ischemia-reperfusion METHODS:A jejunal sac was formend in Sperague Dawley rat.A Laser Doppler probe and a tonometer were inserted into the sac thich was filled with saline.The superior mesenteric artery was occluded(SMAO)for 60 minutes followed by 90 minutes of reperfusion.At the end of 60 minutes of SMAO.either 0.2mg/kg of anisodmine or dobutamine was injected into the jejunal sac.Lase Doppler mucosal blood flow and regional PCO2(PrCO2) measurements were made .RESULTS:Mucosal blood flow was significantly increased at 30,60 and 90 minutes of reperfusion(R30,R60,R90)when intraluminal anisodamine or dobutamine was present compared to intraluminal saline only(44&#177;3.3%or 48&#177;4.1%vs 37&#177;2.6%at R30,57&#177;5.0%,57&#177;5.0%or56&#177;4.7%vs45&#177;2.7%at R60,64&#177;3.3%or56&#177;4.2%.vs48&#177;3.4%at R90,respectively P&lt;0.05),Blood flow changes were also reflected by lowering of jejunal PrCO2 measurements after imtraluminal anisodamine or dobutamine compared with that of the saline controls(41&#177;3.1mmHg or 44&#177;3.0mmHg vs49&#177;3.7mmHg at R30,38&#177;3.7mmHg or 40&#177;2.1mmHg vs47&#177;3.8mmHg at R60,34&#177;2.1mmHg or 39&#177;3.0mmHg vs46&#177;3.4mmHg at R90,respectively,P&lt;0.05),Most interesting finding was that there were significantly higher mucosal blood flow and lower jejunal PrCO2 in anisodamine group than those in dobutamine group at 90 minutes of reperfusion(64&#177;3.3%vs56&#177;4.2%for blood flow or 34&#177;2.1mmHg vs39&#177;3.0mmHg for PrCOs,respectively,P&lt;0.05).suggesting that anisodamine had a more lasting effect on mucosal perfusion than dobutamine.CONCLUSION.Intraluminal anisodamine and dobutamine can augment mucosal blood flow during gut I/R and alleviate mucosal acidosis.The results provided benifical effects on the treatment of splanchnic hypoperfusion following traumatic or burn shock.     

Intestinal ischemia induces late preconditioning against myocardial infarction: a role for inducible nitric oxide synthase

OBJECTIVE: We tested the hypothesis that occlusion of the superior mesenteric artery induces late preconditioning against myocardial infarction and examined the effects of pharmacological modifiers of inducible nitric oxide synthase activity on the late preconditioning in anesthetized rats. METHODS: Rats underwent an intestinal ischemia preconditioning protocol (30 min occlusion of the superior mesenteric artery) or were sham-operated. They were subjected to a sustained 30 min of coronary occlusion and 180 min of reperfusion 24 h later. RESULTS: In rats receiving no pharmacological intervention, the percentage of myocardial infarct within the area at risk and left ventricle was 72+/-4% and 31+/-2%, respectively, in sham-operated rats, and these were significantly reduced to 44+/-4% and 23+/-2% (P<0.01) 24 h after intestinal ischemia preconditioning. Myeloperoxidase activity was significantly reduced by intestinal ischemia preconditioning. Administration of aminoguanidine (300 mg/kg, s.c.) or S-methylisothiourea sulfate (3 mg/kg, i.v.), both relative inducible NO synthase inhibitors, 60 or 30 min before sustained myocardial ischemia not only abolished the late preconditioning afforded by intestinal ischemia, but also inhibited the ability of intestinal ischemia preconditioning to significantly reduce neutrophil infiltration. A change in inducible NO synthase activity was not observed in normal myocardium 24 h after intestinal ischemia, but 30 min of coronary occlusion significantly increased the inducible NO synthase activity in the preconditioned group, which was abolished by aminoguanidine or S-methylisothiourea sulfate. CONCLUSIONS: These data provide pharmacological evidence that induction of inducible nitric oxide synthase, following intestinal ischemia, is associated with increased myocardial tolerance to infarction 24 h later.     

The effect of transient intestinal ischemia on inflammatory parameters

BACKGROUND AND AIMS: To determine the early biological changes occurring in intestinal ischemia in vivo. PATIENTS AND METHODS: We studied the effects of acute transient intestinal ischemia in 15 patients undergoing elective open surgery for the treatment of abdominal subrenal aortic aneurysm induced by clamping of the aorta at subrenal level and above the branching of the inferior mesenteric artery. Blocking the blood flow results in hypoperfusion of the inferior mesenteric artery and then to rectal mucosal ischemia. RESULTS: With the introduction of a mucosal ischemic period the basal intestinal mucosal pH decreased during ischemia, and showed a rapid increase during reperfusion to the level preceding ischemia. Parameters were evaluated in blood taken from inferior mesenteric vein. A rectal dialysis was put into the rectum to evaluate eicosanoid concentrations in rectal fluid collected before and during clamping and after declamping. Significant enhancement in plasma level of xanthine, a marker for tissue damage, was observed during reperfusion. Interleukin-6 levels were significantly elevated from 11.28+/-3.4 pg/ml (preischemic) to 109+/-85.9 pg/ml (ischemic) and to 189.33+/-120.24 pg/ml (reperfusion); and tromboxane B(2) levels from 141.57+/-51.20 pg/ml preoperation to 473.01+/-319.01 pg/ml during the surgical procedure. CONCLUSION: These observations indicate that even transient ischemia modifies the inflammatory pattern.     

Antishock and endothelial protective actions of a NO donor in mesenteric ischemia and reperfusion.

Splanchnic artery occlusion (SAO) of the celiac, superior mesenteric, and inferior mesenteric arteries for 2 hr, followed by a 2-hr reperfusion period in cats produces a severe form of circulatory shock characterized by endothelial dysfunction, increased lysosomal leakage, and severe hypotension resulting from release of proteases, oxygen-derived free radicals, and other humoral mediators into the circulation. Administration of 0.75 mg/kg/hr of C873754, a nitric oxide (NO) donor, 10 min prior to reperfusion, significantly attenuated the accumulation of plasma cathepsin D from 12 +/- 3 U/ml in the SAO + vehicle group to 5 +/- 1 U/ml (P < 0.05) in the C87-3754 treated SAO group. A similar attenuation of plasma myocardial depressant factor (MDF) activity was observed in the C87-3754 treated cats (P < 0.02). Administration of C87-3754 significantly increased short term (i.e., 2-hr) survival rate (P < 0.05, compared to the vehicle group). Moreover, C87-3754 attenuated the SAO shock induced decline in release of endothelium-derived relaxing factor (EDRF) from isolated superior mesenteric artery (SMA) rings stimulated by acetylcholine and A23187. Additionally, C87-3754 significantly decreased PMN adherence to the superior mesenteric venous endothelium in vitro. Thus, treatment with the NO donor, C87-3754 reduced the accumulation of humoral mediators into the plasma while significantly attenuating endothelial dysfunction and improving short term survival.     

Intestinal fatty acid-binding protein as a sensitive marker of intestinal ischemia

Determination of the serum level of intestinal fatty acid-binding protein has been used to detect rat intestinal ischemia following ligation or 30-min occlusion of the superior mesenteric artery. The normal values were under the minimal detectable level of less than 2 ng/ml in all the 10 rats. The serum fatty acid-binding protein level increased rapidly, to 340.7 +/- 54.6, 438.5 +/- 40.1, 388.1 +/- 37.4, and 292.2 +/- 95.7 ng/ml (P less than 0.01) at 1, 2, 4, and 8 hr after ligation, respectively. It also increased, to 347.2 +/- 127.7 ng/ml (P less than 0.01) at 1 hr, after a 30-min transient occlusion and then returned to a normal level. Histological studies showed destruction of the villi, disappearance of the mucosa, and transmural necrosis with the progress of time after ligation, while no remarkable morphological change was observed following 30-min transient occlusion. These observations strongly suggest that the intestinal fatty acid-binding protein is a useful biochemical marker for intestinal ischemia, particularly in the early reversible phase.     

Experimental mesenteric ischaemia in sheep: Gut peptide release and haemodynamic changes

Mesenteric ischaemia remains a frequently lethal condition. An improvement in survival is only likely with earlier diagnosis. Even with action upon early diagnosis and re-establishment of circulation, fatal shock often follows. This study was designed to determine the possible role of gastrointestinal regulatory peptides in the haemodynamic pathophysiology of acute mesenteric arterial ischaemia and whether measurement of these peptides would have diagnostic potential. Fourteen anaesthetized sheep were studied, seven with acute superior mesenteric artery (SMA) occlusion and seven with acute superior mesenteric and coeliac artery (SMA + CA) occlusion. Changes in peptide levels and haemodynamic changes were similar in the two experimental groups, but were more pronounced in the more severe ischaemia of SMA + CA occlusion. No major changes in systemic plasma gastrin, pancreatic polypeptide, neurotensin and vasoactive intestinal polypeptide (VIP) occurred during ischaemia. There was, however, a five-fold increase in VIP in portal venous plasma during SMA + CA occlusion. In the reperfusion period there were increases in VIP concentrations in both systemic and portal circulations in both groups. During ischaemia there was a rise in mean arterial pressure and peripheral resistance and a fall in cardiac output. Reperfusion was characterized by systemic and splanchnic vasodilation coincident with the rise in systemic plasma VIP. It is concluded that VIP which is released from the ischaemic intestine is likely to mediate a component of vasodilation seen during reperfusion.     

Superior mesenteric artery occlusion shock in cats: modification of the endotoxemia by antilipopolysaccharide antibodies (anti-LPS)

We measured the time course of elevated plasma LPS concentration caused by a temporary intestinal ischemia using the superior mesenteric artery (SMA) occlusion shock model in anesthetized cats. The systemic plasma LPS increased from 0.075 +/- 0.006 ng/cc to 0.219 +/- 0.026 ng/cc (P less than 0.001) during the occlusion period. On release of the clamp, the plasma LPS concentration rose rapidly to 0.716 +/- 0.122 ng/cc (P less than 0.001) within 20 min. Thereafter, it declined to reach baseline levels after 100-120 min reperfusion. A total of 21 animals received IV 1.0 cc/kg antilipopolysaccharide hyperimmune equine plasma (anti-LPS) either 1.5 hr before the occlusion or at 0, 10, or 20 min after release of the occlusion. Prophylactic anti-LPS prevented any rise in plasma LPS both during and after release of the occlusion. The administration of anti-LPS during the reperfusion period completely reversed the endotoxemia caused by intestinal ischemia within 5-10 min. This rapidity of response to anti-LPS may be important in the previously reported therapeutic benefit of anti-LPS.     

Effects of glucagon, vasoactive intestinal peptide, and vasopressin on villous microcirculation and superior mesenteric artery blood flow of the rat

The effects of the peptide hormones glucagon, vasoactive intestinal peptide, and vasopressin on the microcirculation of single jejunal villi were studied in anesthetized rats. By means of a recently developed in vivo video-microscopy technique, the red blood cell velocity (pretreatment value: 2.1 +/- 0.1 mm X s-1) and the diameter of the red blood cell column (5.5 +/- 0.2 micron) were measured in the villous arcade vessels. From these parameters, an index of blood flow was calculated in order to determine changes in response to intravenous infusions of the peptides. During the infusions of glucagon and vasopressin, simultaneous measurements were made of superior mesenteric artery blood flow and villous arcade flow. Glucagon (1 microgram X kg-1 X min-1) increased villous arcade flow markedly to 150.1 +/- 13.7% of control, while superior mesenteric artery flow remained unchanged. Vasoactive intestinal peptide (1 microgram X kg-1 X min-1) produced a dilation of the arcade vessel with a commensurate reduction of red cell velocity, leaving the flow index unaltered. Vasopressin (14.3 mU X kg-1 X min-1) was found to be a potent vasoconstrictor at the mucosal level, and since red cell velocity also decreased, villous flow was reduced substantially, paralleling a reduction of superior mesenteric artery flow. After the vasopressin infusion, a reactive hyperemia occurred in the villous arcades. No such increase in blood flow was observed in the superior mesenteric artery. From these findings, we conclude that the villous microvasculature is influenced by various hormones and, therefore, must occupy a prominent position in control of the circulation of the small intestine.     

Reperfusion injury after critical intestinal ischemia and its correction with perfluorochemical emulsion ＂perftoran＂

AIM: To investigate the anti-ischemic properties of perfluorochemical emulsion "perftoran" in mesenteric region. METHODS: Experiments were conducted on 146 nonlinear white male rats weighing 200-350 g. Partial critical intestinal ischemia was induced by thorough atraumatic strangulation of 5-6 cm jejunal loop with its mesentery for 90 min. Global critical intestinal ischemia was made by atraumatic occlusion of the cranial mesenteric artery (CMA) for 90 min also. Perftoran (PF, 0.8-1.0 mL per 100 g) in experimental groups or 0.9% sodium chloride in control groups was injected at 75 min of ischemic period. Mean systemic arterial blood pressure (BPM) registration, intravital microscopy and morphological examination of ischemic intestine and its mesentery were performed in both groups. RESULTS: During 90 min of reperfusion, BPM progressively decreased to 27.3±7.4% after PF administration vs 38.6±8.0% in the control group of rats with partial intestinal ischemia (NS) and to 50.3±6.9% vs 53.1±5.8% in rats after global ischemia (NS). During the reperfusion period, full restoration of microcirculation was never registered; parts with restored blood flow had leukocyte and erythrocyte stasis and intra-vascular clotting, a typical "non-reflow" phenomenon. The reduction of mesenteric 50-400 μm feeding artery diameter was significantly less in the PF group than in the control group (24±5.5% vs 45.2±3.6%, P<0.05) 5 min after partial intestinal ischemia. This decrease progressed but differences between groups minimized at the 90th min of reperfusion (41.5±4.2% and 50.3±2.8%, respectively). In reperfusion of rat's intestine, a significant mucosal alteration was registered. Villous height decreased 2.5-3 times and the quantity of crypts decreased more than twice. In the group of rats administered PF, intestinal mucosal layer was protected from irreversible post-ischemic derangement during reperfusion. Saved cryptal epithelial cells were the source of regeneration of the epithelium, which began to cover renewing intestinal villi after 24 h of blood flow restoration. View of morphological alterations was more heterogeneous in CMA groups. CONCLUSION: Systemic administration of perftoran promotes earlier and more complete structural regeneration during reperfusion in rats after partial and global critical intestinal ischemia.