Serum markers for early detection of patients with mesenteric ischemia after cardiac surgery.

OBJECTIVE: Mesenteric ischemia (MESI) is a rare but often fatal complication in patients after cardiac surgery. Non-specific clinical symptoms and lack of specific laboratory parameters complicate the diagnosis. We evaluated potential serum markers for MESI in cardiac surgery patients. METHODS: Between March and October 2012, serial serum samples of 567 elective cardiac surgery patients were collected 1, 24, and 48 h after the operation, and concentrations of potential markers for MESI [α-glutathione-S-transferase (αGST), intestinal fatty-acid-binding protein (iFABP), and D-lactate] were measured retrospectively. In patients requiring laparotomy, blood samples obtained 72, 48, 24, and 12 h before the laparotomy were additionally measured and compared to all other patients (control group). RESULTS: Laparotomy was performed in 18 patients at 11±7 days after cardiac surgery. MESI was found in 9/18 patients. Already 1 h after cardiac surgery, the serum concentrations of D-lactate (37±18 vs. 25±20 nmol/mL, p<0.01) and αGST (82±126 vs. 727±1382 µg/L, p<0.01) in patients undergoing laparotomy were increased compared to the control group. Between patients with and without MESI, differences were only found for iFABP 24 h after cardiac surgery (1.1±0.4 vs. 2.9±0.6 ng/mL, p=0.04) and up to 72 h before laparotomy (0.56±0.72 vs. 2.51±1.96 ng/mL, p=0.01). CONCLUSIONS: D-lactate and αGST were early markers for gastrointestinal complications after cardiac surgery. Before laparotomy, lowered iFABP levels indicated MESI. Routinely used, these markers can help identify patients with gastrointestinal complications after cardiac surgery early, and might be useful for the evaluation of new therapeutic or preventive strategies.

Resveratrol Does Not Protect from Ischemia-Induced Acute Kidney Injury in an in Vivo Rat Model.

BACKGROUND/AIMS: The natural polyphenol resveratrol (RSV) has been shown to ameliorate ischemia/reperfusion (I/R)-induced damage. Therefore, a rat model of I/R-induced AKI equipped with intensive monitoring was utilized to examine direct renal protection by RSV in vivo. METHODS: AKI was induced by bilateral renal clamping (45 min) followed by reperfusion (3 h). Solvent-free RSV was continuously infused intravenously (0.056 and 0.28 mg/kg) in a total volume of 7 ml/kg/h starting from 30 min before renal clamping. At a mean arterial blood pressure below 70 mmHg for more than 5 min, bolus injections of 0.5 ml 0.9% NaCl solution were administered repetitively (max. 5 ml/kg/h). RESULTS: No differences could be found between normoxic control groups with/without RSV. Bilateral renal clamping and subsequent reperfusion caused a progressive rise in creatinine, cystatin C, and CK, a decrease in cellular ATP content and diuresis. Infusion of RSV increased sirtuin 1 expression after ischemia/reperfusion and was associated with decreased blood pressure during ischemia and early reperfusion accompanied by an increased requirement of bolus injections as well as with increased expression of TNFα. CONCLUSION: RSV did not exert protective effects on I/R-induced AKI in the present short-term in vivo rat model. The lack of protection is potentially connected to aggravation of blood pressure instability.

Effect of Glycine, Pyruvate, and Resveratrol on the Regeneration Process of Postischemic Intestinal Mucosa.

BACKGROUND: Intestinal ischemia is often caused by a malperfusion of the upper mesenteric artery. Since the intestinal mucosa is one of the most rapidly proliferating organs in human body, this tissue can partly regenerate itself after the onset of ischemia and reperfusion (I/R). Therefore, we investigated whether glycine, sodium pyruvate, and resveratrol can either support or potentially harm regeneration when applied therapeutically after reperfusion injury. METHODS: I/R of the small intestine was initiated by occluding and reopening the upper mesenteric artery in rats. After 60 min of ischemia and 300 min of reperfusion, glycine, sodium pyruvate, or resveratrol was administered intravenously. Small intestine regeneration was analyzed regarding tissue damage, activity of saccharase, and Ki-67 positive cells. Additionally, systemic parameters and metabolic ones were obtained at selected periods. RESULTS: Resveratrol failed in improving the outcome after I/R, while glycine showed a partial beneficial effect. Sodium pyruvate ameliorated metabolic acidosis, diminished histopathologic tissue injury, and increased cell proliferation in the small intestine. CONCLUSION: While glycine could improve in part regeneration but not proliferation, sodium pyruvate seems to be a possible therapeutic agent to facilitate proliferation and to support mucosal regeneration after I/R injury to the small intestine.

Autodigestion by migrated trypsin is a major factor in small intestinal ischemia-reperfusion injury.

BACKGROUND: The pathophysiological role of pancreatic digestive hydrolases in intestinal ischemia-reperfusion (I/R) injury is still not clear. Here, we studied whether ischemia-induced injury to the small intestine can be explained by the autodigestion hypothesis. MATERIALS AND METHODS: Mesenteric I/R was induced in rats by superior mesenteric artery occlusion (90 min) and reopening (120 min). Thirty minutes before superior mesenteric artery occlusion, aprotinin (14.7 mg/kg), orlistat (5 mg/kg), and their combination or α1-proteinase inhibitor (60 mg/kg) were injected into the lumen of the small intestine. Systemic and vital parameters, intestinal microcirculation, and mucosal barrier function were monitored during the observation phase; markers of small intestinal injury, as well as trypsin-, chymotrypsin-, elastase-, and lipase-like activities in intestinal effluates were assessed at the end. RESULTS: The pattern of small intestinal injury correlated inversely with the local alterations in microvascular tissue perfusion and corresponded with the intestinal distribution of trypsin-like activity. Aprotinin almost completely inhibited trypsin-like activity (P < 0.05) and significantly reduced intestinal tissue injury. Combined with orlistat, it also increased the postischemic blood pressure (P < 0.05) but not the intestinal barrier function. Macroscopic as well as the histologic alterations were decreased by α1-proteinase inhibitor, which significantly improved postischemic blood pressure (P < 0.05). CONCLUSIONS: The I/R-induced pattern of small intestinal injury is likely to result from both local differences in tissue ischemia and the digestive activity of migrated pancreatic trypsin. Therefore, administration of aprotinin and orlistat into ischemic small intestines may be a therapeutic option in patients with a poor diagnosis.

Attenuation of Multiple Organ Damage by Continuous Low-Dose Solvent-Free Infusions of Resveratrol after Severe Hemorrhagic Shock in Rats.

Therapeutic effects of continuous intravenous infusions of solvent-free low doses of resveratrol on organ injury and systemic consequences resulting from severe hemorrhagic shock in rats were studied. Hemorrhagic shock was induced by withdrawing arterial blood until a mean arterial blood pressure (MAP) of 25-30 mmHg was reached. Following a shock phase of 60 min, rats were resuscitated with the withdrawn blood plus lactated Ringer's. Resveratrol (20 or 60 µg/kg × h) was continuously infused intravenously starting with the resuscitation phase (30 min) and continued until the end of the experiment (total treatment time 180 min). Animals of the shock control group received 0.9% NaCl solution. After the observation phase (150 min), rats were sacrificed. Resveratrol significantly stabilized the MAP and peripheral oxygen saturation after hemorrhagic shock, decreased the macroscopic injury of the small intestine, significantly attenuated the shock-induced increase in tissue myeloperoxidase activity in the small intestine, liver, kidney and lung, and diminished tissue hemorrhages (particularly in the small intestine and liver) as well as the rate of hemolysis. Already very low doses of resveratrol, continuously infused during resuscitation after severe hemorrhagic shock, can significantly improve impaired systemic parameters and attenuate multiple organ damage in rats.

Citrate shows protective effects on cardiovascular and renal function in ischemia-induced acute kidney injury.

BACKGROUND: Ischemia and reperfusion (I/R) is one of the major causes of acute kidney injury (AKI). Citrate reduces hypoxia-induced mitochondrial energetic deficits in isolated proximal tubules. Moreover, citrate anticoagulation is now frequently used in renal replacement therapy. In the present study a rat model of I/R-induced AKI was utilized to examine renal protection by citrate in vivo. METHODS: AKI was induced by bilateral renal clamping (40 min) followed by reperfusion (3 h). Citrate was infused at three different concentrations (0.3 mmol/kg/h; 0.6 mmol/kg/h and 1.0 mmol/kg/h) continuously for 60 min before and 45 min after ischemia. Plasma calcium concentrations were kept stable by infusion of calcium gluconate. The effect of citrate was evaluated by biomonitoring, blood and plasma parameters, histopathology and tissue ATP content. RESULTS: In comparison to the normoxic control group bilateral renal ischemia led to an increase of creatinine and lactate dehydrogenase activity and a decrease in tissue ATP content and was accompanied by a drop in mean arterial blood pressure. Infusion of 1.0 mmol/kg/h citrate led to lower creatinine and reduced LDH activity compared to the I/R control group and a tendency for higher tissue ATP content. Pre-ischemic infusion of 1.0 mmol/kg/h citrate stabilized blood pressure during ischemia. CONCLUSIONS: Citrate has a protective effect during I/R-induced AKI, possibly by limiting the mitochondrial deficit as well as by beneficial cardiovascular effects. This strengthens the rationale of using citrate in continuous renal replacement therapy and encourages consideration of citrate infusion as a therapeutic treatment for AKI in humans.

Attenuation of intestinal ischemic injury and shock by physostigmine.

BACKGROUND: Recently, protection in shock (hemorrhagic or septic) by physostigmine has been demonstrated. Here, we studied the protective effect of intravenous infusion of physostigmine in a rat model of severe intestinal ischemia-reperfusion (I/R) injury and shock. MATERIALS AND METHODS: Mesenteric I/R was induced in male Wistar rats by occlusion of the superior mesenteric artery (90 min) and subsequent reperfusion (120 min). Physostigmine (30 or 70 µg/kg) was administered as bolus injection before induction of I/R. One additional group received, subsequent to the bolus of 30-µg/kg physostigmine, a continuous infusion of 60-µg/kg physostigmine till the end of the experiment. RESULTS: Physostigmine at a dose of 70 µg/kg administered before I/R significantly decreased the macroscopically and microscopically visible intestinal damage. In addition to and presumably as a result of this local protective effect, physostigmine prevented shock induced by reperfusion of the ischemically injured intestine. Lower doses (30 µg/kg) or continuous application of physostigmine were less advantageous. CONCLUSIONS: Physostigmine is clearly protective in intestinal I/R injury and shock. However, for this purpose, physostigmine has to be applied at a dose (70 µg/kg), that is, approximately double the amount of the presently used clinical dose.

Proteomic analysis of human bladder epithelial cells by 2D blue native SDS-PAGE reveals TCDD-induced alterations of calcium and iron homeostasis possibly mediated by nitric oxide.

A proteomic analysis of the interaction among multiprotein complexes involved in 2,3,7,8-dibenzo-p-dioxin (TCDD)-mediated toxicity in urinary bladder epithelial RT4 cells was performed using two-dimensional blue native SDS-PAGE (2D BN/SDS-PAGE). To enrich the protein complexes, unexposed and TCDD-exposed cells were fractionated. BN/SDS-PAGE of the resulting fractions led to an effective separation of proteins and protein complexes of various origins, including cell membrane, mitochondria, and other intracellular compartments. Major differences between the proteome of control and exposed cells involved the alteration of many calcium-regulated proteins (calmodulin, protein S100-A2, annexin A5, annexin A10, gelsolin isoform b) and iron-regulated proteins (ferritin, heme-binding protein 2, transferrin). On the basis of these findings, the intracellular calcium concentration was determined, revealing a significant increase after 24 h of exposure to TCDD. Moreover, the concentration of the labile iron pool (LIP) was also significantly elevated in TCDD-exposed cells. This increase was strongly inhibited by the calmodulin (CaM) antagonist W-7, which pointed toward a possible interaction between iron and calcium signaling. Because nitric oxide (NO) production was significantly enhanced in TCDD-exposed cells and was also inhibited by W-7, we hypothesize that alterations in calcium and iron homeostasis upon exposure to TCDD may be linked through NO generated by CaM-activated nitric oxide synthase. In our model, we propose that NO produced upon TCDD exposure interacts with the iron centers of iron-regulatory proteins (IRPs) that modulate the alteration of ferritin and transferrin, resulting in an augmented cellular LIP and, hence, increased toxicity.

Immune stimulation by exogenous melatonin during experimental endotoxemia.

Melatonin has been shown to enhance the immune response under immune-compromised conditions. However, its immune-modulatory effects under inflammatory conditions are unclear at present. Both pro- and anti-inflammation has been reported. To study time-dependent effects of melatonin on the general immune response during endotoxemia in more detail, we used two models in male rats: per-acute endotoxemia was induced by lipopolysaccharide (LPS) bolus injection (2.5 mg/kg), sub-acute endotoxemia by LPS infusion (2.5 mg/kg × h). Melatonin was applied directly before and 2 h after LPS administration (3 mg/kg, each). The LPS-induced formation of the pro-inflammatory cytokines tumor necrosis factor alpha, interferon-gamma, interleukin (IL)-1α/ß, IL-5, and IL-6 and of the anti-inflammatory cytokine IL-10 was further amplified by melatonin, although it was only significant during per-acute endotoxemia. In both models, melatonin had no effect on the LPS-induced nitric oxide release. These findings show that exogenous melatonin is capable of enhancing the general immune response under inflammatory conditions.

Superiority of acetate compared with lactate in a rodent model of severe hemorrhagic shock.

BACKGROUND: Recently, we have shown that the use of lactated Ringer's (LR) solution is inferior to pure Ringer's solution (RS) in treatment of severe hemorrhagic shock in rats. The present study was performed to evaluate whether this is a specific effect of lactate or also applies to another metabolizable anion, namely acetate. MATERIAL AND METHODS: We subjected male Wistar rats to hemorrhagic shock by dropping the mean arterial blood pressure to 25-30 mm Hg for 60 min, resuscitated with acetated Ringer's (AR) solution, LR solution, RS, or normal saline (NS) within 30 min, and further observed the animals for 180 min. RESULTS: Administration of AR solution prolonged median survival to 115 min compared with 50 min for resuscitation with LR solution or 85 and 90 min for NS and RS, respectively. Resuscitation with AR solution and LR solution clearly improved metabolic acidosis compared with NS and RS but tissue injury, indicated by plasma enzyme activities, was most pronounced in the LR solution group, medium in the NS and RS groups, and least in the AR solution group. CONCLUSIONS: In severe hemorrhagic shock, resuscitation with both RS and NS is superior to administration of LR solution but initial outcome is even further improved if AR solution is used. Mere amelioration of the acid-base status by AR solution may explain its superior role compared with RS and NS but cannot be responsible for its superiority compared with LR solution. Here, direct injury by lactate has to be discussed.

Acid-base and electrolyte status during normovolemic hemodilution with succinylated gelatin or HES-containing volume replacement solutions in rats.

BACKGROUND: In the past, several studies have compared different colloidal replacement solutions, whereby the focus was usually on the respective colloid. We therefore systematically studied the influence of the carrier solution's composition of five approved colloidal volume replacement solutions (Gelafundin, Gelafusal, Geloplasma, Voluven and Volulyte) on acid-base as well as electrolyte status during and following acute severe normovolemic hemodilution. The solutions differed in the colloid used (succinylated gelatin vs. HES) and in the presence and concentration of metabolizable anions as well as in their electrolyte composition. METHODS: Anesthetized Wistar rats were subjected to a stepwise normovolemic hemodilution with one of the solutions until a final hematocrit of 10%. Subsequent to dilution (162 min), animals were observed for an additional period (150 min). During dilution and observation time blood gas analyses were performed eight times in total. Additionally, in the Voluven and Volulyte groups as well as in 6 Gelafundin animals, electrolyte concentrations, glucose, pH and succinylated gelatin were measured in urine and histopathological evaluation of the kidney was performed. RESULTS: All animals survived without any indications of injury. Although the employed solutions differed in their respective composition, comparable results in all plasma acid-base and electrolyte parameters studied were obtained. Plasma pH increased from approximately 7.28 to 7.39, the plasma K(+) concentration decreased from circa 5.20 mM to 4.80-3.90 mM and the plasma Cl(-) concentration rose from approximately 105 mM to 111-120 mM. Urinary analysis revealed increased excretion of K(+), H(+) and Cl(-). CONCLUSIONS: The present data suggest that the carrier solution's composition with regard to metabolizable anions as well as K(+), Ca(2+) only has a minor impact on acid-base and electrolyte status after application of succinylated gelatin or HES-containing colloidal volume replacement solutions.

Effects of glycine, pyruvate, resveratrol, and nitrite on tissue injury and cytokine response in endotoxemic rats.

BACKGROUND: Glycine, pyruvate, resveratrol, and nitrite are well-known protective compounds among others in ischemic tissue injury. Here, we compared their effects in acute lipopolysaccharide (LPS)-induced shock in rats to assess whether inhibition of the proinflammatory cytokine response is a prerequisite for their protective actions. MATERIALS AND METHODS: Rats (six or eight per group) were anesthetized, received LPS as an intravenous bolus (2.5 mg/kg), and were observed for 5 h. Glycine, sodium pyruvate, resveratrol, and sodium nitrite were continuously infused starting 30 min before LPS administration. Parameters included histopathologic changes, organ-specific cytokine levels, plasma nitrite and nitrate concentrations, and time courses of biomonitoring parameters, marker enzyme activities, and plasma cytokine concentrations. RESULTS: Glycine, pyruvate, resveratrol, and nitrite enhanced arterial blood pressure after LPS-induced shock. Also, parameters reflecting tissue ischemia were significantly improved and plasma markers of organ injury ameliorated by all substances. Of the plasma cytokine concentrations increased by LPS, some were differently decreased or even further increased by the substances. None of them reduced the elevated plasma nitrite and nitrate concentration. Glycine diminished the increases in tissue cytokine levels organ specifically, pyruvate decreased some cytokine concentrations in all organs, and nitrite significantly affected only a few cytokine concentrations in some organs, whereas the levels of many cytokines were raised by resveratrol. All substances except resveratrol decreased granulocyte infiltrates in the liver. CONCLUSIONS: The present results demonstrate that glycine, pyruvate, resveratrol, and nitrite protect against LPS-induced shock and tissue injury (cell death) in rats and suggest that inhibition of the proinflammatory cytokine response is not mandatory for their protective actions.

Mesenteric ischemia-reperfusion injury: clearly improved hemodynamics but only minor protection of the rat small intestine by (sub)therapeutic heparin sodium and enoxaparin doses.

BACKGROUND: Tissue protection against ischemia (I)/reperfusion (R) injury by heparins can be due to their anticoagulant and/or non-anticoagulant properties. Here we studied the protective potential of the anticoagulant and the non-anticoagulant features of heparin sodium (HepSo) and enoxaparin (Enox) against mesenteric I/R injury in a rat model. MATERIALS AND METHODS: Mesenteric I/R was induced in rats (n = 6 per group) by superior mesenteric artery occlusion (SMAO; 90 min) and reopening (120 min). Therapeutic/clinical and subtherapeutic/non-anticoagulant doses of HepSo (0.25 mg/kg bolus + 0.25 mg/kg × h; 0.05 mg/kg bolus + 0.1 mg/kg × h) or Enox (0.5 mg/kg bolus + 0.5 mg/kg × h; 0.05 mg/kg bolus + 0.1 mg/kg × h) were administered intravenously starting 30 min before SMAO to the end of reperfusion. Systemic/vital and intestinal microcirculatory parameters were measured during the whole experimental procedure, those of small intestine injury at the end. RESULTS: During intestinal reperfusion, mean arterial blood pressure and heart rates were significantly increased by HepSo and, less effectively, by Enox, in a dose-dependent manner. Intestinal microcirculation was only affected by the therapeutic HepSo dose, which decreased the microvascular flow and S(O2) during reperfusion. The subtherapeutic Enox treatment, as opposed to any HepSo dose, most effectively diminished I/R-induced intestinal hemorrhages, myeloperoxidase activity (as a measure of neutrophil invasion), and histopathological changes. CONCLUSION: Therapeutic but, to a lesser extent, also the subtherapeutic doses of both HepSo and Enox clearly improve hemodynamics during mesenteric reperfusion, while intestinal protection is exclusively provided by Enox, especially at its subtherapeutic dose. Alterations in intestinal microcirculation are not responsible for these effects. Thus, non-anticoagulant Enox doses and, preferably, heparin(oid)s unable to affect coagulation, could diminish clinical risks of I/R-induced gastrointestinal complications.

Exposure of primary porcine urothelial cells to benzo(a)pyrene: in vitro uptake, intracellular concentration, and biological response.

More than 90 % of all bladder cancers are transitional cell carcinomas arising from the cells lining the inside of the hollow organ (uroepithelium). Cell cultures from primary urinary bladder epithelial cells (PUBEC) of pigs were established to assess the uptake, intracellular concentration, and subcellular distribution of the environmental pollutant benzo(a)pyrene (BaP). During treatment of the cells with 0.5 µM BaP for up to 24 h, intracellular concentration of BaP increased without saturation but with marked differences between various PUBEC pools. Analysis of BaP uptake by laser scanning microscopy indicated that BaP is rapidly partitioned into the cell membrane, while only a slight but significant increase in BaP fluorescence intensity was observed in the cytosol and nucleus. Spectrofluorometric quantification of BaP in PUBEC using ex situ calibration revealed a strong accumulation of BaP, leading to intracellular concentrations ranging from 7.28 to 35.70 µM in cells exposed to 0.5 µM BaP and from 29.9 to 406.64 µM in cells exposed to 10 µM BaP. These results were confirmed by gas chromatographic mass spectrometric analysis. Apoptotic cell nuclei were assessed by TUNEL analysis to see whether BaP exposure at the given concentrations results in a toxic effect. While apoptotic cells were barely detectable in control epithelial cells, there was a marked elevation in apoptosis in the BaP-exposed cells. In conclusion, a comprehensive study on uptake and quantification of BaP in epithelial cells from pig bladder is reported for the first time. The study may be helpful in understanding the pattern of BaP uptake and distribution in bladder and its possible implication in bladder cancer development.

Free hemoglobin concentration in severe sepsis: methods of measurement and prediction of outcome.

INTRODUCTION: Hemolysis can be induced in sepsis via various mechanisms, its pathophysiological importance has been demonstrated in experimental sepsis. However, no data on free hemoglobin concentrations in human sepsis are available. In the present study we measured free hemoglobin in patients with severe sepsis as well as in postoperative patients using four methods. It was our aim to determine the potential value of free hemoglobin as a biomarker for diagnosis and outcome of severe sepsis in critical illness. METHODS: Plasma concentration of free hemoglobin was determined in patients with severe sepsis (n = 161) and postoperative patients (n = 136) on day 1 of diagnosis and surgery. For the measurement of free hemoglobin, an enzyme linked immunosorbent assay and three spectrophotometric algorithms were used. Moreover, SAPS II- and SOFA scores as well as procalcitonin concentration and outcome were determined. Kaplan-Meier analysis was performed and odds ratios were determined after classification of free hemoglobin concentrations in a high and low concentration group according to the median. For statistical evaluation the Mann-Whitney test and logistic regression analysis were used. RESULTS: In non-survivors of severe sepsis, free hemoglobin concentration was twice the concentration compared to survivors. Thirty-day survival of patients, as evidenced by Kaplan-Meier analysis, was markedly lower in patients with high free hemoglobin concentration than in patients with low free hemoglobin concentration. Best discrimination of outcome was achieved with the spectrophotometric method of Harboe (51.3% vs. 86.4% survival, p < 0.001; odds ratio 6.1). Multivariate analysis including free hemoglobin, age, SAPS II- and SOFA-score and procalcitonin demonstrated that free hemoglobin, as determined by all 4 methods, was the best and an independent predictor for death in severe sepsis (p = 0.022 to p < 0.001). Free hemoglobin concentrations were not significantly different in postoperative and septic patients in three of four assays. Thus, free hemoglobin can not be used to diagnose severe sepsis in critical illness. CONCLUSIONS: Free hemoglobin is an important new predictor of survival in severe sepsis.

Adverse effects of resuscitation with lactated ringer compared with ringer solution after severe hemorrhagic shock in rats.

Lactated Ringer (LR) is a widely used resuscitation fluid that is known to mediate beneficial effects on acid-base balance when compared with normal saline. We here compared LR with the more physiological Ringer solution (RS) regarding acid-base status, hemodynamics, survival, and organ injury following fluid resuscitation subsequent to severe hemorrhagic shock. Anesthetized rats were hemorrhaged to a mean arterial blood pressure of 25 to 30 mmHg within 30 min. After 60 min, they were resuscitated with either RS or LR (three times the shed blood volume) or with RS or LR plus blood (shed blood plus twice its volume) within 30 min. Subsequently, the animals were observed for further 150 min. When the rats were resuscitated with pure LR or RS, all animals of the shock/LR group, but only three of eight shock/RS group rats were dead 100 min later (median survival, 50 ± 13.1 vs. 120 ± 14.1 min; P < 0.05). Coadministration of the shed blood with RS or LR increased the survival rates to 100%. In these blood-resuscitated groups, organ injury, especially of the kidney, was diminished by the use of RS compared with LR. Time-matched acid-base parameters were not different in all shock groups until death of the animals or euthanasia at the end of experimental time. We conclude that, in severe hemorrhagic shock, resuscitation with RS leads to an improved outcome compared with resuscitation with LR, regardless whether blood is coadministered or not.

Adverse effects of α-ketoglutarate/malate in a rat model of acute kidney injury.

Acute kidney injury (AKI) is the most common kidney disease in hospitalized patients with high mortality. Ischemia and reperfusion (I/R) is one of the major causes of AKI. The combination of α-ketoglutarate+malate (αKG/MAL) showed the ability to reduce hypoxia-induced damage to isolated proximal tubules. The present study utilizes a rat model of I/R-induced AKI accompanied by intensive biomonitoring to examine whether αKG/MAL provides protection in vivo. AKI was induced in male Sprague-Dawley rats by bilateral renal clamping (40 min) followed by reperfusion (240 min). αKG/MAL was infused continuously for 60 min before and 45 min after ischemia. Normoxic and I/R control groups received 0.9% NaCl solution. The effect of αKG/MAL was evaluated by biomonitoring, blood and plasma parameters, histopathology, and immunohistochemical staining for kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL), as well as by determination of tissue ATP and nonesterified fatty acid concentrations. Intravenous infusion of αKG/MAL at a cumulative dose of 1 mmol/kg each (146 mg/kg αKG and 134 mg/kg MAL) did not prevent I/R-induced increases in plasma creatinine, histopathological alterations, or cortical ATP depletion. On the contrary, the most notable adverse affect in animals receiving αKG/MAL was the decrease in mean arterial blood pressure, which was also accompanied by a reduction in heart rate. Supplementation with αKG/MAL, which is very protective against hypoxia-induced injury in isolated proximal tubules, does not protect against I/R-induced renal injury in vivo, possibly due to cardiovascular depressive effects.

Toluidine blue for the intraoperative staining of the ureters. Studies on the safe administration in rats.

PURPOSE: Acute cardiovascular events have repeatedly been reported to occur during the intraoperative presentation of the urinary tract with toluidine blue (TB). We here assessed the minimum TB dose required, and its safest and most suitable form of intravenous administration for the intraoperative staining of the ureters in rats. METHODS: TB (0.13, 0.4, 1.3, or 4.0 mg/kg) was administered to anesthetized rats either by intravenous injection within 1 min or by infusion within 10 min. During the experiments,biomonitoring parameters such as electrocardiograms (ECGs)and mean arterial blood pressure (MAP) were recorded,blood gas analysis was performed, and methemoglobin measured. Tissue injury was assessed from released plasma enzyme activities and histopathologically. The intraoperative staining of the ureters was documented photographically,and total urinary excretion and final urine/plasma TB concentrations were determined. RESULTS: Parameters of blood gas analysis, methemoglobin concentrations, and markers of tissue injury were slightly affected by the two highest TB doses but not at all by the lower ones. At doses of ≥0.4 mg/kg, ureters were stained sufficiently. Staining was more intense, and urine excretion of TB higher on average when the dye was injected.The 1-min injection of ≥1.3 mg TB/kg strongly and temporarily decreased the MAP, while the infusions caused lesser effects. Mean ECG parameters were not affected by any TB administration, but one animal developed a temporary bundle branch block after the 1-min injection of 4.0 mg/kg. CONCLUSIONS: In rats, intravenous injection of 0.4 mg TB/kg was sufficient for the intraoperative staining of the urinary tract without the risk of severe cardiovascular and hemodynamic side effects. Provided our results are transferable to humans, the administration of low TB doses could allow its safer clinical use for the intraoperative visualization of the ureters.

Glycine, a simple physiological compound protecting by yet puzzling mechanism(s) against ischaemia-reperfusion injury: current knowledge.

Ischaemia is amongst the leading causes of death. Despite this importance, there are only a few therapeutic approaches to protect from ischaemia-reperfusion injury (IRI). In experimental studies, the amino acid glycine effectively protected from IRI. In the prevention of IRI by glycine in cells and isolated perfused or cold-stored organs (tissues), direct cytoprotection plays a crucial role, most likely by prevention of the formation of pathological plasma membrane pores. Under in vivo conditions, the mechanism of protection by glycine is less clear, partly due to the physiological presence of the amino acid. Here, inhibition of the inflammatory response in the injured tissue is considered to contribute decisively to the glycine-induced reduction of IRI. However, attenuation of IRI recently achieved in experimental animals by low-dose glycine treatment regimens suggests additional/other (unknown) protective mechanisms. Despite the convincing experimental evidence and the large therapeutic width of glycine, there are only a few clinical trials on the protection from IRI by glycine with ambivalent results. Thus, both the mechanism(s) behind the protection of glycine against IRI in vivo and its true clinical potential remain to be addressed in future experimental studies/clinical trials.

A new model of severe hemorrhagic shock in rats.

We here introduce a fixed-pressure model of hemorrhagic shock in rats that maximizes effects on mean arterial blood pressure (MAP) during shock and yet maintains high reproducibility and controllability. The MAP of rats was adjusted to 25 to 30 mm Hg by blood withdrawals during 30 min. After a shock period of 60 min, rats were resuscitated either with lactated Ringer solution (LR) only or with the collected blood 3-fold diluted with LR (LR + blood) and monitored for further 150 min. Throughout the experiment, vital parameters and plasma marker enzyme activities and creatinine concentration were assessed. Thereafter, liver, kidneys, small intestine, heart, and lung were harvested and evaluated histopathologically. Vital parameters, plasma marker enzyme activities, creatinine concentration, and histopathology indicated pronounced but reliable and reproducible systemic effects and marked organ damage due to hemorrhagic shock and resuscitation. In contrast to rats that received LR + blood, which survived the postresuscitation period, rats receiving LR only invariably died shortly after resuscitation. The hemorrhagic shock model we present here maximally affects MAP and yet is highly reproducible in rats, allowing the study of various aspects of hemorrhagic shock and resuscitation under clinically relevant conditions.