The effects of intraportal administration of prostaglandin E1 on liver ischemia and hepatectomy in rats

The effects of intraportal administration of prostaglandin E₁ (PGE₁) on portal venous flow, hepatic arterial flow, peripheral tissue blood flow, and systemic arterial flow before and after 60 min total liver ischemia followed by 70% partial hepatectomy in rats were investigated. Total liver ischemia was induced by occluding the hepatoduodenal ligament for 60 min. PGE₁ at a dose of 0.5 μg/kg/min was infused intraportally for 15 min before inducing hepatic ischemia (preischemic period) and for 60 min after ischemia (postischemic reperfusion period) in the treatment group. Normal saline was infused in the control group. Seventy percent partial hepatectomy was performed during ischemia. Serum biochemical analysis and liver tissue histology were carried out 1, 3, and 24 h, and 1 and 24 h after reperfusion respectively. One-week survival of the PGE₁ group was improved to 70% compared to that of the control group of 30%. Postischemia reperfusion values of portal and peripheral tissue blood flows in the PGE₁ group were 6.33 ± 0.600 ml/min and 27.2 ± 23.5 (arbitrary), and were significantly different from those of the control group of 4.34 ± 0.400 ml/min and 23.5 ± 5.54 (arbitrary), respectively. There was no significant difference in hepatic arterial flow between the two groups. Serum alkaline phosphatase decreased significantly in the prostaglandin group. Histological examination revealed a significant portal venous congestion in the control group 1 and 24 h after reperfusion. The extent of the sinusoidal congestion was also severe in the control group 24 h after reperfusion. It was concluded that PGE₁ has a protective effect against liver damage when the liver was injured by warm ischemia and reperfusion followed by partial resection. Received for publication on May 30, 1997; accepted on July 27, 1998     

Sevoflurane before or after Ischemia Improves Contractile and Metabolic Function while Reducing Myoplasmic Ca2+ Loading in Intact Hearts

Background: Ca2+ loading occurs during myocardial reperfusion injury. Volatile anesthetics can reduce reperfusion injury. The authors tested whether sevoflurane administered before index ischemia in isolated hearts reduces myoplasmic diastolic and systolic [Ca2+] and improves function more so than when sevoflurane is administered on reperfusion.

Methods: Four groups of guinea pig hearts were perfused with crystalloid solution (55 mmHg, 37[degrees]C): (1) no treatment before 30 min global ischemia and 60 min reperfusion (CON); (2) 3.5 vol% sevoflurane administered for 10 min before ischemia (SBI); (3) 3.5 vol% sevoflurane administered for 10 min after ischemia (SAI); and (4) 3.5 vol% sevoflurane administered for 10 min before and after ischemia (SBAI). Phasic myoplasmic diastolic and systolic [Ca2+] were measured in the left ventricular free wall with the fluorescence probe indo-1.

Results: Ischemia increased diastolic [Ca2+] and diastolic left ventricular pressure (LVP). In CON hearts, initial reperfusion greatly increased diastolic [Ca2+] and systolic [Ca2+] and reduced contractility (systolic-diastolic LVP, dLVP/dtmax), relaxation (diastolic LVP, dLVP/dtmin), myocardial oxygen consumption (Mvo2), and cardiac efficiency. SBI, SAI, and SBAI each reduced ventricular fibrillation, attenuated increases in systolic and systolic-diastolic [Ca2+], improved contractile and relaxation indices, and increased coronary flow, percent oxygen extraction, Mvo2, and cardiac efficiency during 60 min reperfusion compared with CON. SBI was more protective than SAI, and SBAI was generally more protective than SAI.     

Mechanisms Underlying Myocardial Stunning

Abstract The effect of myocardial stunning on mitochondrial function was examined in rabbit hearts. After global normothermic ischemia followed by reperfusion, we previously found that mitochondrial high energy phosphate content was not significantly diminished. To determine whether myocardial stunning results from altered excitation-contraction coupling, we examined function and calcium uptake by sarcoplasmic reticulum (SR). Hearts were subjected to global ischemia under normothermic conditions. Ischemic hearts had significantly lower velocity of Ca² + uptake by the SR (V_max36.3 ± 1.94 nmol/min per mg vs 49.3 ± 2.54 nmol/min per mg control) but velocity was restored by reperfusion. Similarly, myocardial ATP content was decreased during ischemia (4.5 ± 1.23 μmol/g dry weight vs 13.6 ± 0.98 μmol/g control) but returned to normal during reperfusion. Incubation of homogenates with 610 μM ryanodine did not alter the difference in V_maxbetween control, ischemic, or reperfused hearts, suggesting that ischemia affects SR Ca² + pumping without affecting Ca² + release. Recovery of calcium uptake during reperfusion also indicates that SR Ca² + ATPase function is not the major cause of myocardial stunning. Potentiated contractions were studied in a Langendorff heart model, revealing that postrest potentiation (PRP) and peak paired-pulse potentiation (PPP) increase as a result of ischemia. On reperfusion, PPP also increased, but there was a decrease in PRP of left ventricular pressure (LVP) and LV dP/dt (PRP LV dP/dt = 127% preischemia vs 112% at 2 min postischemia), indicating than an impairment of an SR function other than Ca² + ATPase occurs during myocardial stunning.     

Mechanism of defective oxygen extraction following global ischemia

Prolonged global ischemia has been shown to result in a defect in oxygen extraction (O₂E) which is not related to postischemic changes in coronary blood flow or ventricular contractility. Possible explanations for this defect include either (1) decreased O₂ delivery due to diffusion barriers, arterial-venous (A-V) shunting, or myocardial flow maldistribution, or (2) an impaired cellular ability to utilize delivered O₂. Studies were carried out in 24 isolated perfused feline hearts divided into three equal groups. Groups I and II were subjected to 60 min of 37°C ischemia; Group III was protected with hypothermia (27°C) and potassium cardioplegia during the 60 min of ischemia. Group II underwent hyperosmolar (340 mOsm) reperfusion with mannitol to improve subendocardial perfusion; Groups I and III had isosmolar postischemic reperfusion. In addition to O₂E determinations, myocardial O₂ (P_mO₂) was monitored continuously by mass spectrometry. Radioactive microspheres were used to measure both A-V shunting and endo/epi flow ratios. Postischemic O₂E was depressed in Group I (70 ± 5% of control) and Group II (70 ± 4% of control) but was unaltered in Group III (105 ± 8% of control). This impairment of O₂E was not associated with increased A-V shunting. P_mO₂ was not different among the three groups excluding diffusion barriers as a likely explanation. Improving transmural myocardial perfusion in Group II did not result in improvement in postischemic O₂E making flow maldistribution an unlikely cause of this defect. The mechanism of defective postischemic O₂E, therefore, must be an impaired capacity for utilization of delivered O₂ at the cellular level.     

The value and limitations of L-arginine infusion on glomerular and tubular function in the ischemic/reperfused kidney

Purpose: The nitric oxide precursor, L-arginine, has been shown to have a salutary effect on ischemia and reperfusion injury in skeletal muscle, skin, and intestines. Because L-arginine also increases renal blood flow, glomerular filtration, and urine flow in experimental animals with normal renal function, we postulated that L-arginine may also improve renal function after renal ischemic injury.Methods: Eighteen adult New Zealand white rabbits weighing 3 to 3.5 kg were subjected to bilateral normothermic renal ischemia by clamping both renal pedicles for 1 hour followed by 2 hours of reperfusion. The animals were randomized into three groups: group I (control, n = 6) received no additional treatment; group II (pretreatment, n = 6) received systemic intravenous L-arginine at 150 mg/kg over 20 minutes before induction of ischemia; group III (posttreatment, n = 6) received systemic intravenous L-arginine at 150 mg/kg over 20 minutes from the onset of reperfusion. Urine flow, creatinine clearance (C_CR), fractional excretion of sodium (FENa), and renal failure index (RFI) were calculated before ischemia and 2 hours after reperfusion, by use of standard formulas. The changes of the various renal parameters were compared among the three groups.Results: Bilateral normothermic renal ischemia for 1 hour produced a significant deterioration of glomerular filtration as evidenced by a C_CR decrease from 11.1 ± 1.8 to 2.49 ± 0.9 ml/min ( p < 0.01), FENa increase from 2.9% ± 1.0% to 20.8% ± 1.5% ( p < 0.01) and RFI increase from 4.0 ± 1.3 to 28.8 ± 2.6 ( p < 0.01). Pretreatment with L-arginine (group II) minimized the deleterious effects caused by ischemia on glomerular filtration (C_CR of 2.49 ± 0.9 ml/min in group I vs 4.95 ± 2.5 ml/min in group II, p < 0.05) and tubular function (FENa of 20.8% ± 1.5% in group I vs 13.0% ± 5.6% in group II and RFI of 28.8 ± 2.6 in group I vs 18.6 ± 8.0 in group II, p < 0.05). Infusion of L-arginine at the onset of reperfusion (group III) produced a significant diuretic effect (urine flow from 32.6 ± 13.4 ml/hr in group I to 63.3 ± 18.8 ml/hr in group III, p < 0.05) and also minimized glomerular damage (C_CR from 2.49 ± 0.9 ml/min in group I to 4.80 ± 1.2 ml/min in group III, p < 0.05); however, no beneficial effect was observed on tubular function.Conclusion: Induction of nitric oxide production by systemic L-arginine infusion can best preserve glomerular and tubular function in the ischemic/reperfused kidney when given before the ischemic insult. (J VASC SURG 1995;21:453-9.)     

Atrionatriuretic peptide improves left ventricular function after myocardial global ischemia-reperfusion in hypoxic hearts

Atrionatriuretic peptide (ANP) is reported to be useful for attenuating myocardial ischemia–reperfusion injury and improving left ventricular function after reperfusion. However, ANP may be either ineffectual or harmful in cases where the myocardium has been chronically hypoxic since birth. This can be a result of the concomitant high levels of cyclic guanosine monophosphate (cGMP) produced within the myocardium. This study aimed to verify the validity of using ANP to improve left ventricular function after myocardial ischemia–reperfusion injury. For this purpose, a cyanotic congenital disease model that was developed using isolated rat hearts was used. Hearts were obtained from Sprague‐Dawley rats that were housed from birth until 6 weeks of age either in a hypoxic environment with 13–14% FiO₂ (hypoxic group) or in ambient air (normoxic group). These hearts were subjected to 30 min of normothermic global ischemia followed by 30 min of reperfusion using the Langendorff technique. Left ventricular functional recovery in hearts administered ANP (0.1 µM) into the reperfusion solution was compared with those hearts that were not administered ANP in both hypoxic (without ANP: n = 6, with ANP: n = 6, with ANP and HS‐142‐1[an antagonist of ANP]: n = 6) and normoxic hearts (without ANP: n = 6, with ANP: n = 6). In the hypoxic hearts, ANP administration improved the percent recovery of the left ventricular developed pressure (76.3 ± 9.2% without ANP vs. 86.9 ± 6.7% with ANP), maximum first derivative of the left ventricular pressure (82.4 ± 1.1% without ANP vs. 95.8 ± 6.5% with ANP), and heart rate (85.6 ± 4.7% without ANP vs. 96.1 ± 5.2% with ANP) after reperfusion. The improvement and recovery of these cardiac functions were closely related to significantly increased levels of postischemic cGMP release after ANP administration. The effect of ANP was blocked by HS‐142‐1. The improvements observed in the hypoxic group were similar to those found in the normoxic group. ANP administration during reperfusion improved left ventricular function after myocardial acute global ischemia–reperfusion equally in both the chronically hypoxic and age‐matched normoxic groups.     

Decrease in acute myocardial ischemia by hyaluronidase in isolated,perfused, rabbit hearts

Hyaluronidase has been reported to reduce infarct size and cellular damage after coronary artery occlusion. The influence of hyaluronidase (H) on experimental myocardial ischemia was studied in isolated perfused rabbit hearts. Changes in ischemic area were assessed by epicardial NADH fluorescence photography, an intrinsic, high-resolution display of myocardial ischemia. Computerized determination of ischemic area was made from standardized photographs. H was begun 5 min after coronary artery ligation at 4 units/ml perfusate. NADH fluorophotographs were taken at 10-min intervals up to 40 min of ischemia. Coronary sinus oxygen tension (P_esO₂) myocardial oxygen consumption (MV? O₂) and coronary flow were determined. After 40 min, the hearts were perfused with a rhodamine solution to indicate areas of myocardial perfusion. In 18 H-treated hearts 55 ± 6% (mean ± SE) of the nonperfused area was ischemic (NADH fluorescent) and the ischemic areas had a patchy distribution. In 26 untreated hearts 86 ± 2% of the nonperfused area was ischemic and the ischemic areas were uniform, (P < 0.001). The distance between perfused and ischemic tissue was 861 ± 76 μm in the H-treated and 359 ± 19 μm in the untreated hearts, (P < 0.001). In the H-treated hearts P_esO₂ increased to 154% of the postligation control while it decresed to 77% in the untreated hearts (P < 0.001). MV? O₂ decreased to 87% of control after ligation in both groups. The H-treated hearts had a further decline of 37% while the untreated hearts had no further change. In the H-treated hearts, coronary flow increased to 150% of the postligation control while it fell to 80% in the untreated group (P < 0.001). We conclude that hyaluronidase increases P_esO₂ and coronary flow while it decreases MV? O₂ during acute ischemia. In hyaluronidase-treated hearts, significant amounts of myocardium remain normoxic within the nonperfused areas.     

Effects of ulinastatin (urinary trypsin inhibitor) on ATP, intracellular pH, and intracellular sodium transients during ischemia and reperfusion in the rat kidney in vivo

Purpose. To investigate the effects of ulinastatin on renal ischemia–reperfusion injury, we monitored the dynamic changes in ATP, intracellular pH (pHi), and intracellular sodium (Nai) in rats in vivo. Methods. Renal ischemia was induced by clamping the abdominal aorta for 30 min followed by reperfusion for 60 min. Ulinastatin, 50 000 U·kg⁻¹ (UTI group), or normal saline (NS group) was infused for 30 min before ischemia. ³¹P- and double quantum ²³Na-NMR were used to monitor ATP, pHi, and Nai. Results. During ischemia, ATP was rapidly depleted and Nai increased to the same extent in both groups. After 60 min reperfusion, Nai in the NS group was almost restored to the preischemic baseline level (117.2 ± 7.4% of the baseline value), but the recovery of ATP was incomplete (60.9 ± 7.7%). The recovery of Nai in the UTI group began earlier than in the NS group with better recovery of ATP. The pHi values showed severe acidosis in the NS group compared with the UTI group during ischemia and reperfusion. As for ultrastructural findings, after 60 min reperfusion, the mitochondria were less swollen and less disorganized with respect to the membrane and the cristae in the UTI group. Conclusion. The transcellular sodium gradient is restored before the ATP level is normalized during postischemic reperfusion. Ulinastatin might protect mitochondrial conformation during ischemia, and facilitate functional recovery of the ionic pump after reperfusion. Received: April 7, 2000 / Accepted: September 13, 2000     

Landiolol, esmolol and propranolol protect from ischemia/reperfusion injury in isolated guinea pig hearts

PURPOSE: Beta blockers are thought to exert beneficial effects on the ischemic heart. The authors examined the effects of landiolol (ONO 1101), a highly selective beta1 antagonist, propranolol, a nonspecific beta blocker, and esmolol, a selective beta1 antagonist, on postischemic contractile recovery. Drugs were given prophylactically. METHODS: Ischemia-reperfusion in isolated guinea pig hearts was induced by stopping the perfusion for 45 min and reperfusing for 60 min. Hearts (n = 7 in each group) were treated with or without propranolol (1 or 10 microM), esmolol (5 or 50 microM), or landiolol (20, 100 or 500 microM) ten minutes before inducing ischemia. RESULTS: At the end of reperfusion, left ventricular pressure (LVP) recovered to 64 +/- 3% of the baseline value in the control group. With 1 and 10 microM propranolol, LVP recovered to 90 +/- 5% and 100 +/- 6% of the baseline value at 60 min after reperfusion, respectively. Fifty microM but not 5 microM of esmolol resulted in restoration of LVP to 97 +/- 17% of the pre-ischemic value at 60 min after reperfusion. In hearts pretreated with 100 and 500 microM landiolol, LVP was restored to 109 +/- 5% and 104 +/- 5% of the baseline value, respectively. Landiolol 100 microM did not depress LVP in the pre-ischemic period. CONCLUSIONS: The present study shows that landiolol, an ultra-short-acting cardioselective beta1 blocker, has cardioprotective effects on ischemia-reperfusion injury in isolated guinea pig hearts. All three beta blockers were equally protective but the intermediate dosage of landiolol preserved LVP during the pre-ischemic period.     

Experimental study in partial liquid ventilation for acute respiratory failure after ischemia reperfusion pulmonary injury in a rabbit model

Partial liquid ventilation (PLV) using perfluorooctylbromide (PFOB) was studied for use in treating experimental animal models in which acute respiratory failure was caused by hypoxia, oleic acid lung injury, or saline lung lavage. Clinical trials are currently being conducted in the United States. We studied the effectiveness of PLV with PFOB in treating acute respiratory failure after ischemia reperfusion pulmonary injury in a rabbit model; left lung ischemia was induced with a hilar clamp. Ninety minute later, the clamp was removed for reperfusion. Fifteen Japanese white rabbits weighing from 2.5 to 3.2 kg were divided into three groups-conventional mechanical ventilation (CMV) after reperfusion, PLV after reperfusion and controls (conventional mechanical ventilation without ischemia reperfusion injury). In the PLV group, a dose of 7 ml/kg PFOB was administered through an endotracheal tube. In the CMV group, PaO₂ value decreased to 79 ± 13 mmHg 120 min after reperfusion, significantly lower than in the PLV group-404 ± 70-or controls ?494 ± 61?. PaCO₂ was significantly higher in the CMV group ?61.9 ± 14.4 mmHg- than in the PLV group-45.7 ± 6.1? or controls-32.1 ±2.2. Peak airway pressure was slightly higher in the CMV group-19.0 ± 4.9-than in the PLV group-18.2 ± 5.4-or controls-16.2 ± 1.8. mPAP/mSAP did not differ significantly among groups. The heart rate decreased in the CMV and PLV groups, but was unchanged in controls. Microscopic studies revealed markedly reduced alveolar hemorrhage, lung fluid accumulation, and inflammatory infiltration in the PLV group, compared to the CMV group. PLV thus is effective in improving gas exchange and preventing pulmonary injury in acute respiratory failure after ischemia reperfusion injury in a rabbit model.     

Decreasing sarcoplasmic reticular calcium gives rise to myocardial protection? —The effect of thapsigargin for myocardial protection under conditions of normothermia—

Deceasing sarcoplasmic reticular (SR) calcium may contribute to the myocardiac protection against ischemia and reperfusion-induced injury. Therefore, using the isolated working rat heart model, we investigated the effect of Thapsigargin (TH)-induced SR calcium diminution on the myocardial protection when added either before onset of ischemia or at time of reperfusion under conditions of normothermic ischemia. Hearts (n=6/group) from male Wistar rats were aerobically (37°C) perfused (20 min) with bicarbonate buffer. In the experimental protocol A, this was followed by a 3 min infusion of St. Thomas’ Hospital cardioplegic solution No. 2 (STS) containing various concentrations of TH. Hearts were then subjected to 34 min of normothermic (37°C) global ischemia and 35 min of reperfusion (15 min Langendorff, 20 min working). Reperfusion cardiac functions at 20 min of working perfusion was measured and compared with the preischemia values. STS added to 0.1 and 0.25 μmol/L TH improved recovery of aortic flow after 20 min reperfusion from 47 ± 3% in the TH free controls to 62 ± 3, 63 ± 2% (n=6) (p<0.05). There was no difference in creatine kinase (CK) leakage during Langendorff reperfusion between the TH treated groups and the control group. In the experimental protocol B, 3 min of cardioplegia without TH and 34 min of ischemia (37°C) were followed by a 10 min Langendorff reperfusion with various concentrations of TH, then 10 min Langendroff reperfusion for washing out, and 20 min working reperfusion. When TH was added to reperfusate the recovery of aortic flow did not change. 0.5 μmol/L TH group had the detelious effect. Thus, TH, when added to the cardioplegia, enhanced myocardial protection. We conclude that lessened uptake of Ca²⁺ into sarcoplasmic reticulum by inhibitors of the Ca²⁺-ATPase pump can decrease ischemia and reperfusion-induced injury.     

The Effect of Direct Hemoperfusion with a Polymyxin B-Immobilized Fiber Column (DHP-PMX Therapy) on Pulmonary Ischemia-Reperfusion Injury in a Canine Model

This study evaluates the effectiveness of direct hemoperfusion with a polymyxin B-immobilized fiber column (DHP-PMX therapy) on warm ischemia-reperfusion injury of the lung using a canine mode.

Materials and Methods: Ten adult mongrel dogs weighing 13–16 kg were used. After a left thoracotomy, the left pulmonary artery and vein were clamped. The left main bronchus was also clamped and then divided, and complete ischemia of the left lung was maintained for 3 h. The left main bronchus was re-anastomosed before reperfusion of the left lung. The right pulmonary artery was ligated immediately after reperfusion of the left lung. The dogs were divided into two groups: the DHP-PMX group (n = 5, DHP-PMX was performed for 120 min, from 30 min before reperfusion to 90 min after reperfusion) and the control group (n = 5). The body temperature of the animals was maintained at 36°C–37°C during the experiment. The PaO₂/FiO₂ (P/F ratio), AaDO₂, and lt-pulmonary vascular resistance (PVR) were measured at 30, 60, 120, 180, and 240 min after reperfusion in both groups, and the two groups were compared. The water content of the lung tissues and histopathology was also analyzed. Results: The P/F ratio decreased remarkably after reperfusion in the control group, and was significantly (p <. 05) lower than that in the PMX-DHF group until 240 min after reperfusion. The AaDO₂ was significantly (p <. 05) lower in the DHP-PMX group than in the control group at 30, 60, and 120 min after reperfusion. The lt-PVR level differed significantly (p <. 05) between the two groups until 240 min after reperfusion. The water content in the control group was significantly (p <. 05) higher than that in the DHP-PMX group at 240 min after reperfusion. Lung tissues at 120 and 240 min after reperfusion were better preserved pathologically in the DHP-PMX group. Conclusion: DHP-PMX therapy reduced warm ischemia-reperfusion injury in the lung using a canine model.     

Sevoflurane before or after ischemia improves contractile and metabolic function while reducing myoplasmic Ca(2+) loading in intact hearts.

BACKGROUND: Ca(2+) loading occurs during myocardial reperfusion injury. Volatile anesthetics can reduce reperfusion injury. The authors tested whether sevoflurane administered before index ischemia in isolated hearts reduces myoplasmic diastolic and systolic [Ca(2+)] and improves function more so than when sevoflurane is administered on reperfusion. METHODS: Four groups of guinea pig hearts were perfused with crystalloid solution (55 mmHg, 37 degrees C): (1) no treatment before 30 min global ischemia and 60 min reperfusion (CON); (2) 3.5 vol% sevoflurane administered for 10 min before ischemia (SBI); (3) 3.5 vol% sevoflurane administered for 10 min after ischemia (SAI); and (4) 3.5 vol% sevoflurane administered for 10 min before and after ischemia (SBAI). Phasic myoplasmic diastolic and systolic [Ca(2+)] were measured in the left ventricular free wall with the fluorescence probe indo-1. RESULTS: Ischemia increased diastolic [Ca(2+)] and diastolic left ventricular pressure (LVP). In CON hearts, initial reperfusion greatly increased diastolic [Ca2+] and systolic [Ca(2+)] and reduced contractility (systolic-diastolic LVP, dLVP/dt(max)), relaxation (diastolic LVP, dLVP/dt(min)), myocardial oxygen consumption (MvO(2)), and cardiac efficiency. SBI, SAI, and SBAI each reduced ventricular fibrillation, attenuated increases in systolic and systolic-diastolic [Ca(2+)], improved contractile and relaxation indices, and increased coronary flow, percent oxygen extraction, MvO(2), and cardiac efficiency during 60 min reperfusion compared with CON. SBI was more protective than SAI, and SBAI was generally more protective than SAI. CONCLUSIONS: Sevoflurane improves postischemic cardiac function while reducing Ca(2+) loading when it is administered before or after ischemia, but protection is better when it is administered before ischemia. Reduced Ca(2+) loading on reperfusion is likely a result of the anesthetic protective effect.     

心肌缺血/再灌注后多巴酚丁胺最佳应用时间探讨

目的 制作大鼠离体心脏缺血/再灌注损伤(ischemia/reperfusion injury,I/RI)模型,比较再灌注后不同时间点给予多巴酚丁胺对心功能和心肌损伤的影响,以探索心肌缺血/再灌注(ischemia/reperfusion,I/R)后给予多巴酚丁胺的最佳时间.方法 雄性SD大鼠36只,按完全随机法分为4组(每组9只),各组在Langendorff灌注装置上建立离体心脏I/RI模型.平衡灌注15 min,缺血30 min,再灌注60 min,于再灌注期采取不同处理措施.单纯I/R组(I/R组)再灌注期全程以克-亨氏(Kreb'sHenseleit,K-H)液灌注;多巴酚丁胺一组(D1组)再灌注5 min时给予多巴酚丁胺灌注30 min,其余时间以K-H液灌注;多巴酚丁胺二组(D2组)再灌注15 min时给予多巴酚丁胺灌注30 min,其余时间以K-H液灌注;多巴酚丁胺三组(D3组)再灌注25 min时给予多巴酚丁胺灌注30 min,其余时间以K-H液灌注.其中,多巴酚丁胺输注剂量均为10 μg· kg-1·min-1.记录各组平衡灌注末(T0),再灌注10 min(T1)、20min(T2)、30min(T3)、60 min(T4)时的血流动力学指标:HR、左室舒张末压(left ventricular end diastolic pressure,LVEDP)、左室发展压(left ventricular developed pressure,LVDP)、左室内压上升/下降最大速率(the maximum rate of left ventricular pressure change,±dp/dtmax)及冠状动脉流量(coronary flow,CF).留取T0～T4各时点冠状动脉流出液,使用乳酸脱氢酶(lactate dehydrogenase,LDH)和肌酸磷酸激酶(creatine kinase,CK)试剂盒测定冠状动脉流出液中LDH和CK的活性.2,3,5-氯化三苯基四氮唑(2,3,5-triphenyl tetrazolium chloride,TTC)染色法测定心肌梗死面积(myocardial infarct size,MIS).Western blot法检测肌浆网钙泵(sarcoendoplasmic reticulum Ca2+-ATPase,SERCA2a)和兰尼碱受体(ryanodine receptors,RyR2)蛋白表达量. 结果 D1组在给予多巴酚丁胺后,HR、LVEDP、LDH、CK、MIS均比I/R组高,差异有统计学意义(P＜0.05);D2组、D3组在给予多巴酚丁胺后,HR、CF、LVDP、±dp/dtmax均高于I/R组,差异有统计学意义(P＜0.05),而LVEDP、LDH、CK、MIS比较,差异无统计学意义(JP＞0.05).多巴酚丁胺各组SERCA2a蛋白表达量和I/R组比较,差异无统计学意义(P＞0.05),而RyR2蛋白表达量则高于I/R组(P＜0.05).D2组与D3组相比在给予多巴酚丁胺后上述指标比较,差异均无统计学意义(P＞0.05). 结论 大鼠心肌FR 15 min时应用多巴酚丁胺要优于其他时间点.在这一时间点用药可以及时而有效地提高大鼠HR,增加CF,改善心肌收缩功能,且不会加重心肌损伤.     

Optimal Pressure for Low Pressure Controlled Reperfusion to Efficiently Protect Ischemic Heart: An Experimental Study in Rats

Recent work has demonstrated the benefit of low pressure (LP) reperfusion to protect the heart undergoing an ischemic insult. The goal of the present study was to determine the optimal pressure for the application of LP reperfusion. Isolated rats hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion with a pressure fixed at 100 cm H₂O (normal pressure [NP] = control group), 85 cm (group LP [low pressure]-85), 70 cm (group LP-70), or 55 cm (group LP-55). Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring lactate dehydrogenase (LDH) and creatine kinase (CK) leakage in the coronary effluents. Functional recovery was progressively and significantly improved with decreased perfusion pressure. Rate-pressure product (RPP) averaged 3765 ± 408, 6824 ± 439, and 12,036 ± 664 mm Hg/min, respectively, among the control, LP-85, and LP-70 groups (P < .001, LP-70 vs other groups). However, RPP collapsed in the LP-55 group. Similarly, necrosis as measured by LDH and CK leakage progressively reduced between LP-100 and LP-70 hearts (P < .01), with a drastic increase in enzyme in the LP-55 group. In conclusion, this study demonstrated that 70 cm H₂O is an optimal LP to improve postischemic contractile dysfunction and attenuate necrosis during reperfusion.     

Possible further reduction in coronary flow velocity reserve in angina pectoris patients after oral glucose loading

Background

Previous studies have suggested an increase in myocardial oxygen demand as a cause of postprandial angina. The purpose of this study was to assess coronary flow velocity reserve (CFVR) in the left anterior descending coronary artery (LAD) before and after glucose ingestion in patients with known significant LAD stenosis.

Methods

Fourteen patients with significant LAD stenosis and 20 subjects without LAD stenosis were enrolled. Transthoracic Doppler echocardiography was performed to measure the average peak diastolic coronary flow velocity (APDV) in the LAD at rest and during adenosine infusion. CFVR was calculated as APDV during adenosine infusion (APDV_ATP) divided by APDV at rest (APDVrest). APDVrest, APDV_ATP, and CFVR were assessed during fasting and 30, 60, and 120 min after a 75-g oral glucose loading.

Results

In patients with LAD stenosis, APDVrest at 30 min after glucose loading was the highest at any time point. However, significant differences were not found in the APDV_ATP among time points in the patients or controls. Consequently, the CFVR in the patients was the lowest at 30 min after glucose loading (fasting, 1.77 ± 0.19; 30 min, 1.48 ± 0.16; 60 min, 1.69 ± 0.17; and 120 min, 1.76 ± 0.19; p < 0.01, ANOVA), as in the controls.

Conclusions

These findings suggested that the value of CFVR in the LAD was reduced after glucose loading. Myocardial risk area supplied by a stenosed coronary artery may be exposed to myocardial ischemia more frequently during oral glucose loading than during fasting in patients with significant coronary artery stenosis.     

Selective adenosine-A2A activation reduces lung reperfusion injury following transplantation

Background: The adenosine-A_2A receptor on the neutrophil is responsible for several anti-inflammatory actions. We hypothesized that DWH-146e, a selective adenosine-A_2A agonist, would reduce lung reperfusion injury following transplantation.MethodsWe used an isolated, whole blood–perfused, ventilated rabbit lung model. Donor rabbits underwent lung harvest after pulmonary arterial PGE₁ injection and Euro-Collins preservation solution flush, and lungs were preserved for 18 hours at 4°C. Group I lungs (n = 9) served as control subjects. Group II lungs (n = 9) were reperfused with whole blood that was first passed through a leukocyte-depleting filter. In group III (n = 9), DWH-146e was added to the blood reperfusate (25 μg/kg) immediately before reperfusion and was administered throughout the reperfusion period (1 μg/kg/min). All lungs were reperfused for 30 minutes.ResultsArterial oxygenation in group II and group III was significantly higher than that of group I after 30 minutes of reperfusion (514.27 ± 35.80 and 461.12 ± 43.77 vs 91.41 ± 20.58 mm Hg, p < .001). Pulmonary vascular resistance was significantly reduced in group III (22,783 ± 357 dynes · s · cm⁻⁵) compared to both group II and group I (31,057 ± 1743 and 36,911 ± 2173 dynes · s · cm⁻⁵, p < .001). Airway compliance was improved in groups II and III when compared to group I (1.68 ± 0.08 and 1.68 ± 0.05 vs 1.36 ± 0.13, p = .03). Microvascular permeability in group III was reduced to 106.82 ± 17.09 compared with 165.70 ± 21.83 ng Evans blue dye per gram of tissue in group I (p = .05). Group III myeloperoxidase activity was 39.88 ± 4.87 compared with 88.70 ± 18.69 ΔOD/g/min in group I (p = .03); group II myeloperoxidase activity was 56.06 ± 7.46.ConclusionsDWH-146e reduced lung neutrophil sequestration and dramatically improved pulmonary graft function. Neutrophils are important components of the inflammatory cascade of reperfusion injury and their source may include both the circulating blood and the lung graft itself. Selective adensosine-A_2A activation interrupts the neutrophil-mediated inflammatory response and reduces lung reperfusion injury following transplantation.     

Does adenosine administration during the early reperfusion period affect ischemic preconditioning?

We hypothesized that the adenosine administration during the early reperfusion period might affect ischemic preconditioning (IPC) and might reduce infarct size and enhance post-ischemic functional recovery. Twenty-four anesthetized rabbits underwent 30 min. normothermic global ischemia with 120 min. reperfusion in a buffer-perfused isolated, paced heart model and divided into four groups. Global ischemic hearts (GI, n = 6) were subjected to 30 min. global ischemia without intervention. Control hearts (n=6) were subjected to perfusion without ischemia. Ischemic preconditioned hearts (IPC, n=6) were subjected to one cycle of 5 min. global ischemia and 5 min. reperfusion prior to global ischemia. IPC + Ado hearts (n=6) received IPC and adenosine administration (100 m mol/L) during 3 min. early reperfusion period. Post-ischemic functional recovery was better in IPC + Ado hearts as compared to GI and IPC hearts, but the effect of post-ischemic functional recovery in IPC + Ado hearts became weaker during 120 min. reperfusion after prolong ischemic insult. Infarct size wre 1.0 ± 0.3% in Control hearts, 32.9 ± 5.1% in GI hearts, 13.8 ± 1.3% in IPC hearts and 8.1 ± 0.9% in IPC + Ado hearts. Infarct size in IPC hearts was significantly decreased (p<0.01) as compared to GI hearts. The reduction rate against myocardial necrosis in IPC + Ado hearts versus GI hearts was higher as compared to IPC hearts versus GI hearts (p<0.001, IPC+Ado hearts vs GI hearts; p<0.01, IPC hearts vs GI hearts; p = ns, IPC + Ado hearts vs Control hearts). These data suggest that adenosine administration during the early reperfusion period reinforce IPC effect and reduce myocardial reperfusion injury. Cardiomyoprotective effects of IPC and exogenous adenosine are exerted during early reperfusion after coronary occlusion in the isolated perfused rabbit hearts.     

Xenon and isoflurane improved biventricular function during right ventricular ischemia and reperfusion

Background: Although anesthetics have some cardioprotective properties, these benefits are often counterbalanced by their negative inotropic effects. Xenon, on the other hand, does not influence myocardial contractility. Thus, xenon may be a superior treatment for the maintenance of global hemodynamics, especially during right ventricular ischemia, which is generally characterized by a high acute complication rate. Methods: The effects of 70 vol% xenon and 0.9 vol% isoflurane on biventricular function were assessed in a porcine model (n=36) using the conductance catheter technique, and the expression of the type B natriuretic peptide (BNP) gene was measured. The animals underwent 90 min of right ventricular ischemia followed by 120 min of reperfusion. A barbiturate‐anesthetized group was included as a control. Results: Cardiac output was compromised in unprotected animals during ischemia by 33±18% and during reperfusion by 53±17%. This was mainly due to impaired contractility in the left ventricle (LV) and increased stiffness. Isoflurane attenuated the increase in stiffness and resulted in a higher preload. In contrast, xenon increased the right ventricular afterload, which was compensated by an increase in contractility. Its effects on diastolic function were less pronounced. Upregulation of BNP mRNA expression was impeded in the remote area of the LV by both isoflurane and xenon. Conclusions: Xenon and isoflurane demonstrated equipotent effects in preventing the hemodynamic compromise that is induced by right ventricular ischemia and reperfusion, although they acted through somewhat differential inotropic and vasodilatory effects.     

Effects of the COX-2 Inhibitor FK3311 on Ischemia—Reperfusion Injury in the Rat Lung

Ischemia–reperfusion injury is induced by activation of the arachidonic acid cascade following the induction of cyclooxygenase-2. This study evaluated the effects of a selective cyclooxygenase-2 inhibitor, FK3311, on warm ischemia–reperfusion injury in the lung. Male Wistar rats were divided into two groups. In the FK3311 group (n = 27), FK3311 (4 mg/kg) was administered intravenously 5 min before ischemia, while in the control group (n = 27) only vehicle was injected. Warm ischemia was induced for 1 h by clamping the left hilus. The arterial oxygen pressure (PaO₂) and saturation (SaO₂) were measured 30 and 120 min after reperfusion. Serum thromboxane B₂ and 6-keto-prostaglandin F_1α were also measured 30 min after reperfusion. Lung specimens were harvested 120 min after reperfusion for histologic examination and polymorphonuclear counts, and immunostained with cyclooxygenase-2. The 1-week survival rate in the two groups was compared. PaO₂ and SaO₂ 30 and 120 min after reperfusion were significantly (p <. 05) better in the FK3311 group. Serum thromboxane B₂ levels were significantly (p <. 05) lower in the FK3311 group. However, there was no significant difference in 6-keto-prostaglandin F_1α. Histologically, tissue damage was mild and polymorphonuclear infiltration was reduced in the FK3311 group compared to the control group. The expression of cyclooxygenase-2 in the alveolar epithelium based on immunostaining was suppressed in the FK3311 group. The 1-week survival rate was significantly (p <. 05) higher in the FK3311 group. We conclude that FK3311 has protective effects on pulmonary ischemia–reperfusion injury, and results in improvement in the 1-week survival rate.