Protective effect of agiotensin II type I receptor antagonist, CV-11974, on ischemia and reperfusion injury of the liver

BACKGROUND: Microcirculatory disturbance has been shown to play a critical role in hepatic ischemia and reperfusion (I/R) injury. Angiotensin II (AngII) is one of the most potent endogenous vasoconstrictors. Angiotensin II type I (AT1) receptor antagonist has been reported to have protective effects on I/R injury of the heart and kidney. However, effect on hepatic I/R injury has not been determined. In this study, we investigate our hypothesis that AT1 receptor antagonist, CV-11974, attenuates hepatic I/R injury. METHODS: Twelve beagle dogs underwent a 2-hr total hepatic vascular exclusion with veno-venous bypass. CV-11974 was given to animals at a dose of 0.002 mg/ kg/min for 5 min followed by 0.001 mg/kg/min for 25 min via portal vein before ischemia (group II, n=6). Nontreated animals were used as the control (group I, n=6). Animal survival, hemodynamics, hepatic tissue blood flow (HTBF), liver function, platelet count, renin activity, and AngII concentration of hepatic vein, energy metabolism, and histopathology were analyzed. RESULTS: Two-week survival was 33% in group I, in contrast, 100% in group II. Mean arterial blood pressure during early reperfusion was maintained, and HTBF after reperfusion was significantly higher in group II. Treatment attenuated liver enzyme release and decrease of platelet count, increased renin and AngII, suppressed ATP degradation during ischemia and enhanced ATP resynthesis after reperfusion. Neutrophil infiltration and histopathological damages were lessened in group II. CONCLUSIONS: Our data demonstrated that the local renin-angiotensin system might play a role in hepatic microcirculation. AT1 receptor blockade with CV-11974 attenuated hepatic microcirculatory disturbance and ameliorated I/R injury.     

入肝血流阻断和全肝血流阻断对肝组织氧压影响

目的 研究兔常温下入肝血流阻断（portal triad clamp,PTC)及全肝血流阻断（total hepatic vascular exclusion,THVE)对肝组织氧压（tissue oxygen pressure,Ptio2)的影响。方法 24只兔均分二组即PTC和THVE组。分别测定二组缺血前、缺血30min及再灌注30min后肝Ptio2值及血清丙氨酸氨基转氨酶（ALT）值变化。结果 PTC和THVE组均表现为肝Ptio2下降，但THVE较PTC组肝Ptio2值下降更显著（P＜0．01）、血清ALT值也明显升高（P＜0．05）。结论 PTC组较THVE组对肝缺血的耐受性增加。     

入肝血流阻断和全肝血流阻断对胆道梗阻兔肝脏损伤的研究

目的 研究入肝血流阻断和全肝血流阻断对胆道梗阻兔肝脏的缺血-再灌注损伤。方法 36只兔随机均分为3组:胆道梗阻组(A组,BCDL)、入肝血流阻断组(B组,PTC)和全肝血流阻断组(C组,THVE)。组织气体分析仪持续测定肝组织氧分压(P_(ti)O_2);全自动生化仪测定血流总胆红素(TBIL)、丙氨酸氢基转氨酶(ALT);光镜观察肝脏病理改变。结果 B、C组在肝血流阻断后,肝 P_(ti)O_2值均明显下降,再灌注 60 min仅恢复到缺血前的 87.5％和 73.4％(P<0.05),C组较 B组肝P_(ti)O_2 值恢复更慢(P<0.05)。B、C两组 ALT值在肝缺血-再灌注期间均有不同程度升高,C组ALT值升高更明显,且与肝细胞损伤的病理学改变相一致。结论 急性胆道梗阻兔行PTC和THVE均可导致肝脏缺血-再灌注损伤,PTC较THVE对肝脏的损伤明显减轻。     

Advantage of ischemic preconditioning for hepatic resection in pigs

BACKGROUND: Ischemic preconditioning (IP) and intermittent inflow occlusion (IO) have provided beneficial outcomes in hepatic resection. However, comparison of these two procedures against warm hepatic ischemia-reperfusion injury has not been studied enough. MATERIALS AND METHODS: Pigs that had undergone 65% hepatectomy were subjected to Control (120 min continuous ischemia, n = 6), IP (10 min ischemia and 10 min reperfusion, followed by 120 min continuous ischemia, n = 6), and IO (120 min ischemia in the form of eight successive periods of 15 min ischemia and 5 min reperfusion, n = 6). We evaluated hepatocyte injury by aspartate aminotransferase, lactate dehydrogenase and hepaplastin test, hepatic microcirculation by hepatic tissue blood flow (HTBF) and endothelin (ET)-1, inflammatory response by tumor necrosis factor-alpha (TNF-alpha), and histopathology after reperfusion. RESULTS: IP prevented hepatocyte injury, HTBF disturbance, and hepatocyte necrosis in histopathology as well as IO. These two groups showed significantly better outcomes than Control. IP produced significantly less ET-1 and TNF-alpha than IO. CONCLUSIONS: IP ameliorated hepatic warm ischemia-reperfusion injury. Furthermore, IP gained more advantages in preventing chemokine production such as ET-1 and inflammatory response over IO. IP could take the place of IO for hepatectomy.     

Role of cyclic nucleotides in ischemia and reperfusion injury of canine livers

BACKGROUND: In a series of canine liver ischemia experiments, we have shown that amelioration of hepatic injury is achievable by the inhibition of vasoconstriction, cytokine production, platelet aggregation, and neutrophil infiltration. Cyclic adenosine diphosphate (cAMP) was considered to be involved in most of these events. In our study, we tested our hypothesis that augmentation of endogenous cAMP by phosphodiesterase (PDE) 3 inhibitor, amrinone (AM), or adenylate cyclase stimulator, NKH477 (NKH), could attenuate ischemia and reperfusion injury of the liver. METHODS: Thirty-six beagle dogs were used. They were divided into group CT (untreated control), group AM, group NKH, and group CB (treated by both agents). AM or NKH were administered i.v. 1 hr before ischemia (group preAM and group preNKH) or 15 min before reperfusion (pos-AM and postNKH). Combination group animals were treated only before ischemia. Animal survival, hepatic tissue blood flow, liver enzymes, platelet counts, energy metabolism, hepatic cAMP and cyclic guanosine 3',5'-cyclic monophosphate levels, and histopathology were analyzed. RESULTS: Two-week animal survival was significantly improved by pre- or posttreatment with either agent. After reperfusion, hepatic tissue blood flow, liver enzyme release, platelet counts, energy metabolism, tissue cAMP levels, and histological architecture were also ameliorated markedly. Combination of both agents induced severe liver damage and lethal hypotension. AM treatment exhibited more protective effects than NKH, particularly when it was given before ischemia. Interestingly, not only cyclic guanosine 3',5'-cyclic monophosphate, were also restored at higher levels after reperfusion by preischemia treatment. CONCLUSIONS: Administration of amrinone or NKH477 maintained hepatic tissue concentrations of cyclic nucleotides, and attenuated ischemia and reperfusion injury of the liver. Thus, regulation of hepatic tissue cyclic nucleotides is an important alternative for prevention of hepatic damage in liver preservation and surgery.     

Attenuation of ischemic injury by N-acetylcysteine preconditioning of the liver

BACKGROUND: Numerous previous studies have established the hepatoprotective properties of N-acetylcysteine (NAC). The present study was designed to investigate the effects of NAC on a warm hepatic ischemia-reperfusion rat model with a focus on the role of cAMP. MATERIALS AND METHODS: Fifty-six male Wistar rats were allocated randomly into the control group (n = 28) or the study group (group NAC, n = 28). Group NAC animals received an intravenous bolus dose of 0.3 mg/g NAC, whereas control animals were given an equal volume of normal saline. Subsequently, 60-min partial liver ischemia was induced by occlusion of blood inflow to the left and middle liver lobes. Aspartate aminotransferase, alanine aminotransferase, and alpha-glutathione S-transferase levels, platelet aggregation, and ischemic tissue cyclic adenosine 5-monophosphate (cAMP) levels were examined at 30, 60, and 120 min after reperfusion. Parts of the ischemic liver were sampled at the same time-points. Measurements were obtained from seven animals at each time point. RESULTS: The administration of NAC resulted in lower levels of aspartate aminotransferase, alanine aminotransferase, and alpha-glutathione S-transferase, decreased platelet aggregation, and increased levels of ischemic tissue cAMP at all time points after reperfusion. Histologically, fewer necrotic changes were observed in the NAC group at 60 and 120 min after reperfusion. All differences were statistically significant (P < 0.05). CONCLUSIONS: In the present study, NAC seems to attenuate hepatic ischemia-reperfusion damage, as demonstrated by liver function tests and liver histology. The effects of NAC appear to be mediated by the decrease in platelet aggregation and increase in the levels of cAMP observed in ischemic liver tissue.     

Post-ischemic intraportal adenosine administration protects against reperfusion injury of canine liver

Although adenosine has been postulated to inhibit ischemia-reperfusion injury in various tissues, its in vivo cytoprotective mechanism is not fully known. The aim of this study was to determine the effect of intraportally infused adenosine on reperfusion injury in the canine liver. Two h ischemia and reperfusion of the liver were induced in beagle dogs by clamping the portal triad. Either adenosine or saline was infused in the portal vein after reperfusion for 60 min. Levels of serum aspartate aminotransferase and alanine aminotransferase and the survival of animals were examined. Hepatic levels of protein carbonyls and glutathione were also measured, as markers of oxidative stress. One h after reperfusion, the liver was perfused with nitroblue tetrazolium and the formation of formazan was observed to evaluate superoxide formation. Twenty-four h after reperfusion, 100% of animals in the adenosine group and 33% of animals in the control group survived. Adenosine significantly decreased the reperfusion-induced increase in serum levels of aspartate aminotransferase and alanine aminotransferase. Adenosine also suppressed the formation of protein carbonyls and the decrease in glutathione levels. Histologically, neutrophil infiltration, superoxide formation, and apoptosis were decreased by adenosine. These results suggest that intraportally infused adenosine attenuates reperfusion injury of the liver, presumably by suppressing the activation of neutrophils and oxidative stress. Received for publication on Oct. 15, 1999; accepted on Nov. 11, 1999     

Ozone oxidative preconditioning is mediated by A1 adenosine receptors in a rat model of liver ischemia/ reperfusion

The liver is damaged by sustained ischemia in liver transplantation, and the reperfusion after ischemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the role of A₁ adenosine receptor on the protective actions conferred by OzoneOP in hepatic I/R. By using a specific agonist and antagonist of the A₁ subtype receptor (2-chloro N6 cyclopentyladenosine, CCPA and 8-cyclopentyl-1,3-dipropylxanthine, DPCPX respectively), we studied the role of A₁ receptor in the protective effects of OzoneOP on the liver damage, nitiric oxide (NO) generation, adenosine deaminase activity and preservation of the cellular redox balance. Immunohistochemical analysis of nuclear factor-kappa B (NF-κB), tumor necrosis factor alpha (TNF-α) and heat shock protein-70 (HSP-70) was performed. OzoneOP prevented and/or ameliorated ischemic damage. CCPA showed a similar effect to OzoneOP + I/R group. A₁AR antagonist DPCPX blocked the protective effect of OzoneOP. OzoneOP largely reduced the intensity of the p65 expression, diminished TNF-α production, and promoted a reduction in HSP-70 immunoreactivity. In summary, OzoneOP exerted protective effects against liver I/R injury through activation of A₁ adenosine receptors (A₁AR). Adenosine and ^.NO produced by OzoneOP may play a role in the pathways of cellular signalling which promote preservation of the cellular redox balance, mitochondrial function, glutathione pools as well as the regulation of NF-κB and HSP-70.     

Attenuation of liver and lung injury after hepatic ischemia and reperfusion by a cytokine-suppressive agent, FR167653

BACKGROUND: Hepatic ischemia/reperfusion (I/R) injury is an important clinical problem and leads to the release of the proinflammatory cytokines, TNF-alpha and IL-1. These cytokines play important roles in the induction of polymorphonuclear neutrophil (PMN) activation and infiltration, and induce not only localized hepatic injury but also remote organ injury, especially pulmonary injury. Using a total hepatic ischemia model in rats, we tested our hypothesis that suppression of TNF-alpha and IL-1 by FR167653 ameliorates I/R injury in the liver and lung. METHODS: Male Wistar rats, weighing 240-280 g, were divided into 3 groups, an FR group, a control group and a sham group. In the FR group, FR167653 (1 mg/kg/h) was administered continuously to the animals for 30 min prior to the onset of ischemia and for 2 h after reperfusion. The control group received normal saline. A porto-systemic shunt was placed between the cecal branch of the portal vein and the jugular vein, and total hepatic ischemia was produced for 90 min. The sham group was treated with placement of the porto-systemic shunt only. The 1-week survival rate, liver enzyme activity, hepatic tissue blood flow (HTBF), cytokine mRNA expression, myeloperoxidase (MPO) activity and histological results were studied. RESULTS: The 1-week survival rate and HTBF were significantly higher in the FR group than in the control group. Serum AST, ALT, and LDH levels were significantly lower in the FR group at 30 min, 1 h and 3 h after reperfusion. MPO levels in liver and lung tissue were also significantly lower in the FR group. The expression of IL-1beta mRNA remarkably decreased up to 6 h after reperfusion in the FR group. CONCLUSIONS: We concluded that the inflammatory cytokines, IL-1beta, play important roles in hepatic I/R injury. FR167653 might ameliorate I/R injury and be useful in liver surgery with ischemia.     

Preconditioning protects against ischemia/reperfusion injury of the liver

Ischemic preconditioning (IPC) of an organ may induce protection against the injury caused by longer duration of ischemia and subsequent reperfusion. In a standardized model of such injury in the rat liver, we used the following protocol to investigate whether adenosine played a role in IPC by preventing its enzymatic degradation by dipyridamole pretreatment according to the following protocol: group 1, non-ischemic control rats; group 2, ischemic control rats subjected to 60 minutes of ischemia by clamping of the common hepatic artery followed by 60 minutes of reperfusion; group 3, IPC with 10 minutes of ischemia followed by 15 minutes of reperfusion, prior to the ischemia/reperfusion period as in group 2; group 4, pharmacologic preconditioning with administration of dipyridamole prior to the ischemia/reperfusion period as in group 2. Peripheral liver blood flow was significantly reduced during clamping (groups 2 to 4). After unclamping, blood flow was still reduced in the ischemic rats (group 2) but had returned to preclamp values in the animals that had been subjected to ischemic (group 3) or pharmacologic (group 4) preconditioning. Liver cell injury was significantly increased in the ischemia group (group 2) only. In our experimental model of ischemia/reperfusion injury in the rat liver, we found an equally beneficial effect with ischemic and pharmacologic preconditioning. Adenosine appears to be a crucial factor in IPC.     

Contribution of endothelin-1 to microcirculatory impairment in total hepatic ischemia and reperfusion injury

BACKGROUND: Endothelin (ET)-1 may have a role in hepatic polymorphonuclear leukocyte infiltration as well as microcirculatory disturbance during hepatic ischemia-reperfusion (HIR) injury. This study was conducted to investigate the influence of ET-1 on the hepatic microcirculation after total HIR and to evaluate the effect of a nonselective ET receptor antagonist under these conditions. METHODS: Male rats pretreated with either normal saline (NS group) or TAK-044, a nonselective ET receptor antagonist (TAK group), were subjected to 120 min of total hepatic ischemia with extracorporeal portosystemic shunting. RESULTS: Plasma ET-1 levels increased significantly from 1 to 6 hr after reperfusion in the NS group when compared with the nonischemic control. In the early phase of reperfusion, the NS group showed significantly narrower sinusoids, lower hepatic tissue blood flow, a lower hepatic tissue oxy-hemoglobin concentration, and more hepatic neutrophil infiltration than the TAK group (P<0.05). Pretreatment with TAK-044 improved hepatic microcirculatory derangement, and resulted in significantly better 7-day survival (61.5%) with more bile production after reperfusion when compared with the NS group (P<0.01). CONCLUSIONS: The present study demonstrated that ET-1 is involved in the development of HIR injury by causing deterioration of the hepatic microcirculation. A nonselective ET receptor antagonist successfully ameliorated HIR injury through improvement of hepatic oxygenation and of the microcirculation along with reduced hepatic neutrophil infiltration.     

Transfer of the interleukin-1 receptor antagonist gene into rat liver abrogates hepatic ischemia-reperfusion injury

BACKGROUND: The anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1Ra) is known to reduce hepatic ischemia-reperfusion injury. Therefore, we wished to examine the effect of IL-1Ra gene delivery into the rat liver on hepatic ischemia-reperfusion injury. METHODS: IL-1Ra cDNA was delivered into the rat liver by a single injection of the transgene vector into the portal vein using either the plasmid-cationic liposome or the recombinant adenoviral vector. At 24 hours after the gene delivery, rats were subjected to partial liver ischemia for 90 minutes followed by reperfusion. Liver tissue and serum samples were taken at 180 minutes of reperfusion, and the degree of the liver injury as well as the expression level of pro-inflammatory cytokines in the serum and tissue were investigated. In addition, we assessed the effect of IL-1Ra gene delivery on the 7-day survival rate when the nonischemic liver lobe was partially excised immediately following reperfusion. RESULTS: In both cases of delivery methods, gene transfer of IL-1Ra resulted in significant elevation of serum IL-1Ra concentration, which reached maximal levels at 24 hours following the delivery. However, the highest serum concentration with the adenoviral vector was 1,000-fold of that in the liposome-treated animals. In the IL-1Ra delivered rats, liver damage, as well as production of pro-inflammatory cytokines, at 180 minutes of reperfusion was significantly reduced in a concentration-dependent manner of the circulating IL-1Ra protein. Rats subjected to the adenoviral vector gene delivery had higher 7-day survival rates compared with control animals. CONCLUSIONS: IL-1Ra gene delivery into the liver may be of therapeutic use for abrogating hepatic ischemia-reperfusion injury after transplantation.     

Attenuation of renal ischemia–reperfusion injury by postconditioning involves adenosine receptor and protein kinase C activation

Significant organ injury occurs after transplantation and reflow (i.e., reperfusion injury). Postconditioning (PoC), consisting of alternating periods of reperfusion and re‐occlusion at onset of reperfusion, attenuates reperfusion injury in organs including heart and brain. We tested whether PoC attenuates renal ischemia–reperfusion (I/R) injury in the kidney by activating adenosine receptors (AR) and protein kinase C (PKC). The single kidney rat I/R model was used. Groups: (1) sham: time‐matched surgical protocol only. In all others, the left renal artery (RA) was occluded for 45 min and reperfused for 24 h. (2) Control: I/R with no intervention at R. All antagonists were administered 5 min before reperfusion. (3) PoC: I/R + four cycles of 45 s of R and 45 s of re‐occlusion before full R. (4) PoC + ARi: PoC plus the AR antagonist 8‐ρ‐(sulfophenyl) theophylline (8‐SPT). (5) PoC + PKCi: PoC plus the PKC antagonist chelerythrine (Che). In shams, plasma blood urea nitrogen (BUN mg/dl) at 24 h averaged 23.2 ± 5.3 and creatinine (Cr mg/dl) averaged 1.28 ± 0.2. PoC reduced BUN (87.2 ± 10 in Control vs. 38.8 ± 9, P = 0.001) and Cr (4.2 ± 0.6 in Control vs. 1.5 ± 0.2, P < 0.001). 8‐SPT and Che reversed renal protection indices after PoC. I/R increased apoptosis, which was reduced by PoC, which was reversed by 8‐SPT and Che. Postconditioning attenuates renal I/R injury by adenosine receptor activation and PKC signaling.     

Mild hypothermia ameliorates lung ischemia reperfusion injury in an ex vivo rat lung model

BACKGROUND: Ischemia reperfusion (I-R) injury of the lung frequently occurs after cardiopulmonary bypass, pulmonary thromboendarterectomy, lung transplantation, and major pulmonary resection with vascular reconstruction. Mild hypothermia ameliorates ischemia reperfusion injury of the brain and the liver. However, the effect of mild hypothermia on I-R injury of the lung has not been investigated. METHODS: The lungs of Lewis rats underwent 80 min of ischemia followed by 60 min of reperfusion in an ex vivo perfusion model. The ambient temperature was maintained at either normothermia (38 degrees C, n=6) or mild hypothermia (35 degrees C, n=6) during the ischemia and reperfusion. RESULTS: Pulmonary shunt fraction, peak inspiratory pressure, mean pulmonary arterial pressure during reperfusion, and the wet/dry weight ratio of the lung tissue at the end of reperfusion in the mild hypothermia group were significantly (p<0.05) lower than those in the normothermia group. Total adenine nucleotide, adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate after reperfusion in the mild hypothermia group were significantly (p<0.05) higher than those in the normothermia group. CONCLUSION: Mild hypothermia attenuates I-R injury of the lung with maintained levels of intrapulmonary high-energy phosphate compounds after reperfusion, suggesting its beneficial effect on warm lung I-R in clinical settings.     

Pentoxifylline contributes to the hepatic cytoprotective process in rats undergoing hepatic ischemia and reperfusion injury.

AIM: Considerable efforts have been made to find and/or eliminate the underyling causes of hepatic ischemia-reperfusion injury, but many points are still unclear. Pentoxifylline-related cytoprotection is one of these unclear points. Our study tests the effects of pentoxifylline on the hepatic cytoprotective process in an experimental model. MATERIALS AND METHODS: The animals were divided into two groups: (1) placebo-pretreated rats and (2) pentoxifylline-pretreated rats. After pretreatment, all rats underwent the hepatic ischemia-reperfusion procedure which was performed by clamping the hepatoduodenal ligament. To evaluate the liver injury, serum levels of alanine transaminase (ALT) and aspartate transaminase (AST), and liver tissue levels of prostaglandin E(2) (PGE(2)) were measured before ischemia, immediately after ischemia and immediately after reperfusion. RESULTS: Before ischemia and immediately after ischemia, there were no significant differences between ALT and AST levels of groups 1 and 2 (p >0.05). However, at the end of reperfusion, ALT and AST levels of group 2 were significantly decreased when compared with group 1 (p < 0.05 and p < 0.01, respectively). Additionally, tissue levels of PGE(2) that were obtained before ischemia, immediately after ischemia and immediately after reperfusion in group 2 were significantly higher than those of group 1 (p < 0.001). CONCLUSION: Pentoxifylline reduces reperfusion injury of the liver through significantly decreased transaminase levels, and contributes to hepatic cytoprotection by increasing tissue levels of PGE(2) significantly. These effects reflect the role of tissue PGE(2) in pentoxifylline-related hepatoprotection against ischemia-reperfusion injury of the liver.     

Attenuation of ischemia and reperfusion injury of canine livers by inhibition of type II phospholipase A2 with LY329722

BACKGROUND: Membrane phospholipid breakdown, caused by ischemia and reperfusion (I/R) of the liver, releases free fatty acids including arachidonic acids and lysophospholipids, which serve as precursors of various inflammatory lipid derivatives. Phospholipase A2 (PLA2) is a key enzyme that initiates this reaction. In this study, we tested our hypothesis that a type II PLA2 inhibitor, LY329722, could attenuate hepatic I/R injury caused by a 2-hr total hepatic vascular exclusion (THVE) in dogs. METHODS: Eighteen beagle dogs, subjected to a 2-hr THVE, were divided into three groups. Group 1 (n=6) was untreated and served as a control group. LY329722 was administered to animals in group 2 (n=6) intravenously (0.2 mg x kg(-1) x hr(-1)) for 60 min before ischemia, and to animals in group 3 (n=6) for 60 min starting 15 min before reperfusion (0.2 mg x kg(-1) x hr(-1)). Animal survival, systemic and splanchnic hemodynamics, hepatic tissue blood flow, liver functions, energy metabolism, hepatic venous thromboxane B2 and endothelin-1 levels, phospholipid levels and tumor necrosis factor-a mRNA expression in liver tissue, and histopathologic findings were evaluated. RESULTS: Two-week animal survival was 33% (two of six) in group 1, and 100% (six of six) in groups 2 and 3. LY329722 improved systemic and splanchnic hemodynamics, hepatic tissue blood flow, and energy metabolism, reduced liver enzyme, thromboxane B2, and endothelin-1 release, prevented hepatic phospholipid degradation and tumor necrosis factor-alpha mRNA expression, and lessened histopathologic damage and the number of neutrophil infiltrating into the liver tissue. CONCLUSION: The present study demonstrated that a type II PLA2 inhibitor, LY329722, attenuated hepatic I/R injury caused by a 2-hr THVE model in dogs.     

Experimental evaluation of the effects of the intraportal administration of cyclic guanosine monophosphate on ischemia/reperfusion in the porcine liver

This study was done to examine the protective effects of cyclic guanosine monophosphate (cGMP), a second messenger of nitric oxide, for ischemia/reperfusion injury of the liver, since it is known to induce vasodilatation and to inhibit platelet aggregation. Using an experimental model of porcine liver ischemia, 8-bromoguanosine 3′,5′ monophosphate, a cGMP analog, was continuously administered into the portal vein before ischemia and after reperfusion 30 min for each in the cGMP group (n=6). Saline water was administered in the same way in the control group (n=6). The cardiac output (CO), mean arterial blood pressure (MAP), portal venous flow (PVF), hepatic arterial flow (HAF), hepatic tissue blood flow (HTBF), and hepatic tissue cGMP level were determined. Hepatic enzymes and the bile discharge were also assessed as indicators of hepatic function. The hepatic tissue cGMP level was significantly higher, and PVF, HTBF, and the bile discharge were significantly greater in the cGMP group, while there were no remarkable differences between the groups with CO, MAP, HAF, and hepatic enzymes. In conclusion, the continuous supplementation of cGMP into the portal vein was found to be beneficial for preserving both the hepatic circulation and, consequently, the hepatic function of after warm ischemia of porcine liver.     

Dynamic changes of post-ischemic hepatic microcirculation improved by a pre-treatment of phosphodiesterase-3 inhibitor, milrinone

BACKGROUND: Phosphodiesterase-3 inhibition has been shown to attenuate hepatic warm ischemia-reperfusion injury. The aim of this study was to investigate the effect of milrinone, phosphodiesterase-3 inhibitor, on post-ischemic microcirculation of rat livers by intravital microscopy. MATERIALS AND METHODS: Male Wistar rats were randomly assigned to three groups; group A, milrinone pre-treatment; group B, ischemic pre-conditioning; and group C, no pre-treatment. All animals underwent a 60-min warm ischemia of the left lateral liver lobe. Microvascular perfusion and leukocyte-endothelial interaction were observed by intravital videomicroscopy. Hepatocellular viability and cellular damage were quantified by adenosine triphosphate tissue concentration as well as alanine aminotransferase and lactate dehydrogenase blood levels, respectively. RESULTS: In groups A and B, cyclic AMP hepatic tissue concentration was elevated significantly. After reperfusion, microvascular perfusion in hepatic sinusoids was significantly better maintained, and the number of adherent leukocytes was reduced in sinusoids and in post-sinusoidal venules in these rats. Serum transaminase blood levels were suppressed significantly in these groups compared with controls. CONCLUSION: The demonstrated improvement of hepatic microcirculation is certainly derived from milrinone induced cell protection in ischemia reperfusion of the liver. This effect is outlined by improved energy status and reduced liver enzyme liberation and mimics the effect of ischemic pre-conditioning.     

Novel nitric oxide donor (FK409) ameliorates liver damage during extended liver resection with warm ischemia in dogs

BACKGROUND: Nitric oxide attenuates ischemia-reperfusion injury by maintaining organ circulation through its actions as a vasoregulator, an inhibitor of platelet aggregation, and an attenuator of leukocyte adhesion. Otherwise, the harmful effects of enhanced nitric oxide production induced by inducible nitric oxide synthase mediate ischemia-reperfusion injury. FK409 has been characterized as a spontaneous nitric oxide donor. The aim of this study was to evaluate the effects of FK409 on extended liver resection with ischemia using a canine model. STUDY DESIGN: Adult mongrel dogs were subjected to 60 minutes of warm ischemia by partial inflow occlusion. After reperfusion the nonischemic lobes were resected and the remnant liver function was evaluated. The dogs were divided into two groups: the control group (n = 7) and the FK409 group (n = 6), which was given FK409 through the portal vein. RESULTS: The hepatic tissue blood flow, serum liver enzymes levels, and serum endothelin-1 level after reperfusion were significantly better in the FK409 group than in the control group. Electron microscopy demonstrated that endothelial cells and Ito cells were well-preserved in the FK409 group. The 3-day survival rate was statistically better in the FK409 group (67%) than in the control group (14%). CONCLUSIONS: FK409 appears to have protective effects during extended liver resection with ischemia.     

缺血预处理对骨骼肌缺血再灌注损伤的保护机制及其与腺苷关系研究

目的 :探讨骨骼肌缺血预处理保护作用机制及其腺苷的关系。方法 :采用兔右后肢缺血模型 ,将 2 8只兔随机分为 4组 (n =7) ,对照组 :持续缺血 4h ,再灌注 1h ;预处理组 :缺血 5min ,再灌注 5min ,重复 3次后 ,持续缺血 4h再灌注1h。腺苷治疗组 :于缺血再灌注前经股动脉注入 0 5mg腺苷。腺苷受体拮抗剂 8-PT处理组 :在 3次循环IPC处理前 ,经股动脉注入 3 0mg 8-PT ,再缺血 4h ,再灌注 1h。通过高效液相色谱法测定处理前、缺血 4h ,再灌注 10min、3 0min及6 0min时血浆腺苷浓度变化。通过血浆CPK、MDA及骨骼肌99mTcMDP吸收量的测定判断骨骼肌损伤程度。结果 :预处理组、腺苷组及 8-PT组 ,在缺血 4h和再灌注 1h期间血浆腺苷浓度明显升高 (P <0 0 1) ,再灌注 10min时达到高峰 ,并随再灌注时间延长而逐渐降低。与对照组相比 ,预处理组和腺苷组血浆CPK、MDA及骨骼肌99mTcMDP吸收量显著降低 (P <0 0 1)。结论 :腺苷参与了缺血预处理对骨骼肌的保护作用 ,腺苷受体拮抗可阻断缺血预处理对骨骼肌的保护作用。腺苷释放和腺苷受体激活在骨骼肌缺血预处理中起重要作用。