Insufficient Oxygen Delivery Research Articles

Vascular Endothelial Growth Factor as Marker for Tissue Hypoxia and Transfusion Need in Anemic Infants: A Prospective Clinical Study

Oxygen-carrying capacity of blood is reduced in anemic infants because of low hemoglobin levels. Red blood cell transfusions become necessary if low hematocrit causes tissue hypoxia. No reliable parameters exist for detecting chronic tissue hypoxia. Vascular endothelial growth factor is upregulated by hypoxia; hence, elevated vascular endothelial growth factor levels may be a marker for tissue hypoxia and may indicate the need for red blood cell transfusions. In a prospective study, plasma vascular endothelial growth factor levels were measured in 3 groups of infants suspected of requiring red blood cell transfusions to find a vascular endothelial growth factor cutoff value indicative of tissue hypoxia. The 3 groups were acute anemic (an episode of acute bleeding [hematocrit drop > 5%] per day); chronic anemic (hematocrit drop < 5% per day); and nontransfused (hematocrit drop < 5% per day) but not meeting clinical criteria for a transfusion. Blood was sampled before transfusion and again 48 hours after transfusion if required. Plasma vascular endothelial growth factor and erythropoietin concentrations were measured. Vascular endothelial growth factor concentrations were lower in acutely anemic compared with chronically anemic infants, whereas erythropoietin levels did not differ between these groups. The vascular endothelial growth factor concentration was <140 pg/mL in all acutely anemic infants, and this was deemed the threshold level indicating sufficient tissue oxygenation in subsequent analysis. We found that 30% of chronically anemic and 43% of nontransfused infants had vascular endothelial growth factor levels of >140 pg/mL. In transfused infants, with elevated vascular endothelial growth factor levels, red blood cell transfusion resulted in lowering of vascular endothelial growth factor concentrations. Vascular endothelial growth factor concentrations of >140 pg/mL may indicate insufficient oxygen delivery to tissues and may serve as a marker of the need for transfusion or of tissue hypoxia in other diseases.

Hypoxia upregulates expression of human endosialin gene via hypoxia-inducible factor 2

Endosialin is a transmembrane glycoprotein selectively expressed in blood vessels and stromal fibroblasts of various human tumours. It has been functionally implicated in angiogenesis, but the factors that control its expression have remained unclear. As insufficient delivery of oxygen is a driving force of angiogenesis in growing tumours, we investigated whether hypoxia regulates endosialin expression. Here, we demonstrate that endosialin gene transcription is induced by hypoxia predominantly through a mechanism involving hypoxia-inducible factor-2 (HIF-2) cooperating with the Ets-1 transcription factor. We show that HIF-2 activates the endosialin promoter both directly, through binding to a hypoxia-response element adjacent to an Ets-binding site in the distal part of the upstream regulatory region, and indirectly, through Ets-1 and its two cognate elements in the proximal promoter. Our data also suggest that the SP1 transcription factor mediates responsiveness of the endosialin promoter to high cell density. These findings elucidate important aspects of endosialin gene regulation and provide a rational frame for future investigations towards better understanding of its biological significance.

Cancer-Associated Carbonic Anhydrases and Their Inhibition

Cells of the growing tumor tissue are exposed to physiological stresses connected with insufficient delivery of oxygen (hypoxia) and accumulation of acidic products of the glycolytic metabolism (acidosis). Adaptation to these microenvironmental stresses involves remodeling of the cellular expression program mediated by hypoxia-inducible factor (HIF), which activates broad array of genes functionally involved in angiogenesis, anaerobic glycolysis, de-adhesion, invasion etc. This leads to increased aggressiveness of tumors, metastatic spread and poor response to therapy. Genes coding for transmembrane carbonic anhydrase (CA) isoforms IX and XII are induced in response to low oxygen as a part of the hypoxic transcriptome. Moreover, CA IX is a direct target of HIF and serves as a surrogate marker of hypoxia and prognostic indicator. Its expression is strongly linked to different types of tumors with the HIF pathway activated due to genetic defect or physiological hypoxia. CA IX (and possibly also CA XII) is participates in pH regulation, which is important for survival of hypoxic cells. Both enzymes are therefore promising therapeutic molecules targetable by inhibitors of CA activity. Some of these sulfonamide compounds and their derivatives are capable to block CA-mediated pH regulation in hypoxia. This review summarizes research data related to distribution, regulation and functional aspects of CA IX and CA XII, and describes emerging possibilities for clinical exploitation of CA inhibitors as imaging tools and anticancer drugs.

OPTICAL SPECTROSCOPY DEMONSTRATES ELEVATED INTRACELLULAR OXYGENATION IN AN ENDOTOXIC MODEL OF SEPSIS IN THE PERFUSED HEART

Recent clinical studies of patients with sepsis have shown that the delivery of adequate oxygen alone does not necessarily result in improved organ function or survival. This study was undertaken to determine if optical spectroscopy could detect higher intracellular oxygenations in isolated, perfused guinea pig hearts that have been treated with endotoxin (lipopolysaccharide [LPS]) than in controls. Four hours after intraperitoneal injection with LPS, adult guinea pigs were anesthetized, and hearts were excised and perfused in the Langendorff manner. Six control and eight LPS-exposed guinea pigs were studied. Myoglobin oxygen saturation was determined from analysis of optical reflectance spectra acquired from the left ventricular free wall. Myoglobin saturation was significantly higher at baseline with LPS than in controls (96.0% +/- 0.8% vs. 89.4% +/- 1.7%, P < 0.001). At the end of 30 s of ischemia, myoglobin saturation decreased to 15% +/- 1% in controls, but to only 60% +/- 7% in the LPS group. Myocardial performance was determined by measured left ventricular developed pressure, which was significantly depressed in the LPS-exposed hearts relative to controls (30 +/- 4 mmHg vs. 67 +/- 9 mmHg, P < 0.001). Myocardial oxygen consumption, calculated from measurements of arterial and venous PO2 and coronary flow, was lower in LPS hearts relative to controls (0.199 +/- 0.021 mL oxygen x min(-1) x g(-1) vs. 0.157 +/- 0.006 mL oxygen x min(-1) x g(-1)). In this model of sepsis in the perfused guinea pig heart, intracellular oxygenation was higher and oxygen consumption was lower than in controls. Cellular dysfunction seen in sepsis may be caused by compromised oxygen use rather than insufficient oxygen delivery. Optical spectroscopy has the potential to noninvasively monitor patients and their responses to therapy.

Hyperoxia Improves Oxygen Consumption in the Detached Feline Retina

To investigate the effects of hyperoxia on retinal oxygenation and oxygen consumption in the detached feline retina. Retinal detachment was created in nine intact anesthetized cats by injecting 0.25% sodium hyaluronate in balanced salt solution into the subretinal space. Oxygen microelectrodes were used to collect spatial profiles of retinal Po(2) in both the attached and detached retina. A diffusion model was fitted to quantify photoreceptor oxygen consumption (Q(av)). In the detached retina, the Po(2) at the border between the retina and the fluid layer under the retina decreased; hyperoxia increased it to a level that was not significantly different from the control (attached retina, air breathing). Detachment did not change the Po(2) at the border between the avascular and vascularized retina; hyperoxia significantly increased the level. Oxygen consumption decreased to 47% +/- 18% of the control value in the detached retina during normoxia; hyperoxia increased Q(av) to 68% +/- 17% of control. Hyperoxia increased the average inner retinal Po(2) (P(IR)) in the detached retina to a level higher than that during normoxia. Detachment did not change P(IR) during normoxia. Hyperoxia has been shown to improve photoreceptor survival in the detached retina. The present work suggests that hyperoxia is protective because it allowed increased photoreceptor oxygen consumption. Whereas normal Po(2)s were maintained at the inner and outer border of the avascular region during hyperoxia, Q(av) was not restored to normal, suggesting that other factors are involved in photoreceptor dysfunction during detachment in addition to insufficient oxygen delivery.

Central Nervous System Dysfunction after Noncardiac Surgery and Anesthesia in the Elderly

Central Nervous System Dysfunction after Noncardiac Surgery and Anesthesia in the Elderly

Efficacy of Tokishakuyakusan on the Anemia in the Iron-Deficient Pregnant Rats

Iron-deficiency anemia not only causes insufficient oxygen delivery to the body of the mother, but creates serious conditions in the fetus, such as insufficient oxygen delivery and poor development, and its treatment has become an important issue. To elucidate the mechanism of the anemia-ameliorating action of Tokishakuyakusan, we investigated the effect of administration of Tokishakuyakusan on anemia-related parameters and the serum transferrin and erythropoietin levels, erythrocyte morphology, and bone marrow cells in pregnant rats and in pregnant rats with iron-deficiency anemia. The results showed that Tokishakuyakusan significantly improved the low erythrocyte count, hemoglobin, and hematocrit values of the pregnant rats in the iron-deficient state, increased the proportion of normal erythrocytes in terms of erythrocyte morphology, increased the proportion of erythroblasts among bone marrow cells, and also significantly increased the erythropoietin and transferrin levels in the blood. These findings suggested that Tokishakuyakusan promotes erythrocyte differentiation in iron-deficiency anemia, and that it possesses anemia-ameliorating efficacy.

Physiological correlates of intellectual function in children with sickle cell disease: hypoxaemia, hyperaemia and brain infarction

Lowered intelligence relative to controls is evident by mid-childhood in children with sickle cell disease. There is consensus that brain infarct contributes to this deficit, but the subtle lowering of IQ in children with normal MRI scans might be accounted for by chronic systemic complications leading to insufficient oxygen delivery to the brain. We investigated the relationship between daytime oxyhaemoglobin saturation (SpO2), cerebral blood flow velocity (CBFV) and intellectual function (IQ) using path-analysis in 30 adolescents with sickle cell disease (mean age 17.4 years, SD 4.2). Initial analyses revealed that the association between SpO2 and Full Scale IQ (FSIQ) was fully mediated by increased CBFV, whereby SpO2 was negatively correlated with CBFV and CBFV was negatively correlated with FSIQ, i.e. decreases in oxygen saturation are associated with increases in velocity, and increased velocity is associated with lowered IQ scores. The mediated relationship suggests that lowered IQ may be a function of abnormal oxygen delivery to the brain. Further analyses showed that the association between CBFV and IQ was significant for verbal but not for performance IQ. The pathophysiology characteristic of SCD can interfere with brain function and constrain intellectual development, even in the absence of an infarct. This supports the hypothesis that lowered intellectual function is partly explained by chronic hypoxia, and has wider implications for our understanding of SCD pathophysiology.

Hyperlactatemia during cardiopulmonary bypass: determinants and impact on postoperative outcome

IntroductionHyperlactatemia during cardiopulmonary bypass is relatively frequent and is associated with an increased postoperative morbidity. The aim of this study was to determine which perfusion-related factors may be responsible for hyperlactatemia, with specific respect to hemodilution and oxygen delivery, and to verify the clinical impact of hyperlactatemia during cardiopulmonary bypass in terms of postoperative morbidity and mortality rate.MethodsFive hundred consecutive patients undergoing cardiac surgery with cardiopulmonary bypass were admitted to this prospective observational study. During cardiopulmonary bypass, serial arterial blood gas analyses with blood lactate and glucose determinations were obtained. Hyperlactatemia was defined as a peak arterial blood lactate concentration exceeding 3 mmol/l. Pre- and intraoperative factors were tested for independent association with the peak arterial lactate concentration and hyperlactatemia. The postoperative outcome of patients with or without hyperlactatemia was compared.ResultsFactors independently associated with hyperlactatemia were the preoperative serum creatinine value, the presence of active endocarditis, the cardiopulmonary bypass duration, the lowest oxygen delivery during cardiopulmonary bypass, and the peak blood glucose level. Once corrected for other explanatory variables, hyperlactatemia during cardiopulmonary bypass remained significantly associated with an increased morbidity, related mainly to a postoperative low cardiac output syndrome, but not to mortality.ConclusionHyperlactatemia during cardiopulmonary bypass appears to be related mainly to a condition of insufficient oxygen delivery (type A hyperlactatemia). During cardiopulmonary bypass, a careful coupling of pump flow and arterial oxygen content therefore seems mandatory to guarantee a sufficient oxygen supply to the peripheral tissues.

Is oxygen insufficiency compensated during acute ischemia? - A PET study in an ischemic model of non-human primates

Insufficient delivery of oxygen to tissue is the central core of ischemia. A large number of observations in rodents revealed that compensatory responses against ischemia occurs at cellular or biochemical level, however, there is a lack of in vivo evidences of biological responses to fulfil oxygen demand. Among them, vascular response to maintain the delivery (e.g. vasodilatation) and transport efficiency of metabolic substrates from blood to tissue assumed to be fundamental (Hayashi et al. 2003). Here, we show using PET whether there is response in vasculature or in the diffusion efficiency of oxygen in an acute stroke model in non-human primates. We used four adult male macaque monkeys (macaca fascicularis, body weight = 5 kg). The study was approved by the local committee of animal experiments. Experiments were performed under general anesthesia using propofol. A single PET scan with dual tracer/integration (DTI) method for CBF/CMRO2 and a PET scan for CBV were repeatedly performed before and 360 min after the artificial embolization of intracerebral artery. Embolization was produced by injecting autologous blood clot through a thin catheter placed at middle cerebral artery or internal carotid artery. Ischemic of interest (ROI) were defined by searching voxels with the highest values in the oxygen extraction fraction (OEF) images at the time point of 5 min or 180 min after embolization. CBF, CMRO2 and CBV values were also obtained by placing the same ROI to the corresponding images. CBV values were used for the assessment of vascular response, whereas effective oxygen diffusibility (EOD) that was calculated from measured CBF, OEF and arterial haemoglobin content (Hb) and oxygen saturation fraction (Sa) was used as a marker of efficiency of oxygen transport from blood to brain tissues (Hayashi et al. 2003). The values were normalized by ROI values in cerebellum for each image and by the values at the time point of pre-embolization for each subject to minimize measurement- and subject-specific variability. The mirror contralateral to the ROI were used for control. Ischemic (n = 7) showed decrease in CBF (-30%, -32% at 5 min and 180 min, respectively) and CMRO2 (-18%, -10%) and increase in OEF (+18%, +26%) compared to the control. CBV values showed no change (+1%, +2%) whereas EOD decreased (-12%, -11%). When the regions were divided in two categories by the final tissue outcome (non-infarcted or infarcted), significant decreases in CBF, CMRO2 and EOD were found in the of final infracted, but no difference in CBV were seen between the two categories. Similar results were also obtained in the other time points (30, 60, 120, 210 and 360 min post embolization). These results reveal that in acute ischemic there is little response in vasculature and that change in diffusion efficiency of oxygen does not act as a compensatory response rather passively depends on the metabolic demand, although oxygen extraction fraction is increased. The findings indicate that brain tolerance for oxygen insufficiency is not so large that oxygen metabolism during ischemia correlates final tissue outcome.

Gastric Tonometry in the Care of the Newborn

Gastric Tonometry in the Care of the Newborn

Sublethal actions of copper in abalone ( Haliotis rufescens) as characterized by in vivo 31P NMR

The sublethal biochemical actions of copper in live, intact red abalone ( Haliotis rufescens) were characterized by in vivo 31P nuclear magnetic resonance spectroscopy (NMR). This non-invasive technique is ideal for examining cellular respiration since critical metabolite concentrations, including phosphoarginine ([PA]), inorganic phosphate ([P i]) and [ATP], and the arginine kinase (AK) rate constant, can be monitored in real time. Both metabolite concentrations and enzyme rate constants were measured in abalone during 8-h exposures to 66 μg l −1 (1.04 μM) and 126 μg l −1 (1.98 μM) copper (as CuCl 2). Significant decreases in [PA] and corresponding increases in [P i] resulted, while [ATP] remained constant. In controls [PA], [P i] and [ATP] all remained unchanged. Furthermore, both copper concentrations induced a significant elevation in the forward AK rate constant over the basal value of 0.020±0.002 s −1. Metabolite levels and enzyme rate constants were also measured during 8-h 66 μg l −1 copper exposures both before and after a 2-week subchronic exposure to 36 μg l −1 (0.57 μM) copper. Unlike before the subchronic exposure, no significant changes in [PA], [P i] or [ATP] were observed after the 36 μg l −1 copper treatment, compared with controls. This induced tolerance was also evident from the forward AK rate constant data. Finally, copper accumulation was determined in gill, digestive gland and foot muscle samples. Whereas acute exposure only led to significant accumulation in the gill, copper levels in subchronically exposed abalone were significantly elevated in both the gill and digestive gland, and marginally so in foot muscle. Overall, the gill appears to be the primary site of copper accumulation and toxicity, while the foot and adductor muscles maybe secondarily impacted. The observed metabolic changes may result from insufficient oxygen delivery to the muscles, resulting from mucus accumulation or cytological damage at the gill. In conclusion, abalone acutely exposed to copper pollution may develop asphyxial hypoxia. Since their survival is dependent on adherence to rock surfaces, such a reduction of muscle function could ultimately prove fatal.

Renal pathology in hemizygous sickle cell mice.

Transgenic mice have been developed that express exclusively human sickle cell beta hemoglobin and have major pathological features found in humans with sickle cell disease. These mice provide a unique opportunity to investigate the fundamental mechanisms of this disease and to design new strategies to correct the associated genetic defect(s). We found that in breeding males expressing only adult human alpha-globin and sickle beta-globin (homozygous SS mice) with females containing these transgenes plus one copy of the mouse beta-globin gene (hemizygous SS mice) greater than expected numbers of hemizygous offspring were produced than homozygous mice (carrying no mouse beta-globin gene). These hemizygous mice, expressing the human alpha and sickle beta(s) transgenes in combination with mouse beta+/-, were used for our preliminary studies of their renal pathology. No kidney lesions were found in the control (129/Sv) mice, whereas about 50% of the hemizygous SS mice showed mild-to-severe kidney lesions, including glomerulonephritis, cystic atypical hyperplastic tubules, and general nephropathy. Kidneys of some hemizygous mice were normal or showed minimal nephropathy, yet those of the susceptible phenotype developed a mild-to-more-severe form of renal lesions. The tubular epithelium of kidneys of hemizygous mice of the more affected phenotype exhibited increased expression of inducible nitric oxide synthase with an increased 3-nitrotyrosine in close proximity. There was also a stronger immunostaining for vascular cell adhesion molecule-1 in the interstitial capillary cells as well as the tubular epithelial cells of the renal cortex, compared with normal control mice. The occurrence of a high incidence of renal abnormalities in our hemizygous SS mice suggests that these mice may provide a suitable model to study the pathogenesis of nephropathy resulting from altered blood flow and/or insufficient oxygen delivery.

Reduced mitochondrial adenosine triphosphate synthesis in skeletal muscle in patients with child-pugh class B and C cirrhosis

Patients with cirrhosis of the liver often complain of tiredness and a lack of strength at physical exercise. Other investigators have found that muscle strength, work capacity, and maximal oxygen consumption are reduced in cirrhosis. We hypothesized that mitochondrial maximal rate of ATP synthesis in skeletal muscle may be impaired in these patients. This was tested with 31P nuclear magnetic resonance spectroscopy in anterior tibial muscle of cirrhotic patients and healthy controls at rest, during exercise, and subsequent recovery. In patients with Child-Pugh class B and C cirrhosis resting PCr/Pi ratio (8.3 ± 1.0; n = 7) was lower than in patients with Child-Pugh class A cirrhosis (12.1 ± 2.1; n = 7) and controls (11. 7 ± 1.1; n = 6; P = .03), while the resting Pi/γATP ratio was higher in Child-Pugh class B and C patients (0.43, 0.30, and 0.27, respectively; P = .03). Maximal rate of mitochondrial adenosine triphosphate (ATP) synthesis (Vmax) as calculated from the initial rate of phosphocreatine (PCr) recovery after work was lower in Child-Pugh class B and C cirrhosis (0.189 mmol/L/s ± 0.034) than in both Child-Pugh class A patients (0.402 mmol/L/s ± 0.103) and controls (0.425 mmol/L/s ± 0.064; P = .01). Vmax was significantly correlated to intracellular free [Mg2+] obtained from the 31P nuclear magnetic resonance (NMR) spectra (P = .003). Insufficient oxygen delivery did not seem a likely cause of reduced ATP synthesis in the patients. These findings suggest either a decreased number of mitochondria in skeletal muscle of the cirrhotic patient in Child-Pugh class B and C or a defective mitochondrial function that could be related to low intracellular free [Mg2+]. (HEPATOLOGY 2001;34:7-12.)

ASIC3: a lactic acid sensor for cardiac pain.

Angina, the prototypic vasoocclusive pain, is a radiating chest pain that occurs when heart muscle gets insufficient blood because of coronary artery disease. Other examples of vasoocclusive pain include the acute pain of heart attack and the intermittent pains that accompany sickle cell anemia and peripheral artery disease. All these conditions cause ischemia – insufficient oxygen delivery for local metabolic demand — and this releases lactic acid as cells switch to anaerobic metabolism. Recent discoveries demonstrate that sensory neurons innervating the heart are richly endowed with an ion channel that is opened by, and perfectly tuned for, the lactic acid released by muscle ischemia[1,2].

Skeletal muscle fibres as factors for pork quality

Interaction between muscle fibres, perimortem energy metabolism and different environmental factors determine postmortem transformation from muscle to meat. Muscle fibres are not static structures, but easily adapt to altered functional demands, hormonal signals, and changes in neural input. Their dynamic nature makes it difficult to categorise them into distinct units. It must be realised that some properties may change without affecting others or without changing histochemical appearance of a given fibre such as species specificity, developmental or adaptive processes or pathological conditions, and that transient fibre types exist. Therefore, a distinction between specific types must strictly refer to the method that has been used for the typing. Theoretically, there will be at least as many fibre types as there are motor units in a muscle, and within a muscle a fibre type may show a continuum of structural and functional properties which overlap with other fibre types. Histochemical and biochemical properties of a muscle, such as fibre type composition, fibre area, oxidative and glycolytic capacities, and glycogen and lipid contents, are factors that have been found to influence meat quality. An important factor for post-mortem changes and meat quality is the metabolic response that takes place in the different fibre types pre-slaughter. Selection for leaner pigs and for a higher proportion of large muscle fibres, especially of type IIB, can result in poor capillarisation and consequently an insufficient delivery of oxygen and substrates and elimination of end products, such as CO2 and lactate, and thereby a reduced pork quality. In the future, fibre types in pig muscle will probably be investigated with more advanced and sensitive techniques, which makes it is possible to look at adaptations in different contractile, sarcoplasmic proteins as well as other muscle proteins that are of importance for cell differentiation and muscle cell metabolism. Furthermore, single fibre dissection and quantitative biochemical analyses may increase the knowledge about metabolic and contractile properties of the muscle fibre. The literature indicates possibilities to include muscle fibre characteristics in breeding schemes for improved meat quality, while preserving optimal production traits. In order to use muscle fibre characteristics in a beneficial way for future breeding programmes, further investigations are needed to better understand the physiological mechanisms. Selection experiments based on biochemical and histochemical characteristics determined in biopsies or otherwise and study of the correlated selection responses, may possibly provide better tools to study these relationships.

Changes in Intramucosal Ph and Gut Blood Flow During Whole Body Heating in a Porcine Model

Heat stroke is a syndrome which reduces systemic vascular resistance and cardiac collapse. The gut plays an important role in shock. In hyperthermia, many of the same symptoms as heat stroke may be present, including inhibition of splanchnic vasoconstriction and endotoxemia. Furthermore, both conditions result in shock, in which the gut plays an important role. Detection of insufficient oxygenation of gut tissue, which sustains an earlier and more severe hypoxia, can warn of impending shock and can be performed by monitoring intramucosal pH (pHim). This index is very sensitive to tissue hypoxia and ischemia. In the present study both pHim, using tonometry, and gut blood flow during whole body heating (WBH) in pigs were measured. WBH was achieved by circulating warm water through a vinyl sheet covering the animal. Central venous pressure was maintained by fluid infusion. Body temperature was measured using a thermometer probe inserted into the right jugular vein. Mean arterial pressure, cardiac output and gut blood flow were also measured. pHim was evaluated using a tonometer placed into the midileum lumen. During WBH, cardiac index and mean arterial pressure increased, however systemic vascular resistance decreased. Gut blood flow was either maintained at the normal rate or increased. Intraarterial pH did not change significantly, however pHim significantly decreased from 7.30 at the beginning of WBH to approximately 7.05 after the body temperature reached 42.5°C. These findings suggest that there was reduced oxygen delivery to the tips of the small intestinal villi during regional ischemia following WBH. In conclusion, insufficient tissue oxygen delivery as detected by a reduction in inramucosal pH is an important index in whole body heating.

Glycine minimizes reperfusion injury in a low-flow, reflow liver perfusion model in the rat

This study investigated the effects of glycine on reperfusion injury in a low-flow, reflow liver perfusion model. With this protocol, livers were perfused at low flow rates of approximately 1 ml.g-1. min-1 for 75 min, which caused cells in pericentral regions of the liver lobule to become anoxic because of insufficient delivery of oxygen. When normal flow rates (approximately 4 ml.g-1.min-1) were restored for 40 min, an oxygen-dependent reperfusion injury occurred. Upon reflow, lactate dehydrogenase (LDH), a cytosolic enzyme, and malondialdehyde (MDA), an end product of lipid peroxidation, were released into the effluent perfusate. LDH increased from basal levels of approximately 1-35 IU.g-1.h-1 in livers from control rats. Glycine (0.06-2.00 mM) minimized enzyme release in a dose-dependent manner (half-maximal decrease = 133 microM), with maximal values only reaching 5 IU.g-1.h-1 when glycine was increased to 2 mM. Reflow for 40 min after 75 min of low-flow hypoxia caused death in approximately 30% of previously anoxic parenchymal cells in pericentral regions; however, infusion of glycine (2 mM) decreased cell death to less than 10%. Strychnine (1 mM), which was found to mimic the cytoprotective effect of glycine in proximal renal tubules, also reduced LDH release to 11 IU.g-1.h-1 in this study. Bile was released at rates of approximately 42 microliters.g-1.h-1 in livers from control rats, but values were not altered significantly by glycine. Maximal MDA production during reperfusion decreased by 35% with 0.6 mM of glycine. Trypan blue distribution time, an indicator of hepatic microcirculation, was reduced significantly by glycine at 5 and 40 min after reflow, but changes were about twofold greater at later time points compared with earlier ones (half-maximal decrease = 225 microM). Time for oxygen to reach steady state upon reflow was reduced by glycine in a dose-dependent manner, and the rates of entry and exit of a dye confined to vascular space (fluorescein dextran) were increased two- to threefold by glycine, respectively. Taken together, these data indicate that a reperfusion injury that occurs in previously hypoxic pericentral regions of the liver upon reintroduction of oxygen is minimized by glycine, possibly by action on a glycine-sensitive anion channel to improve microcirculation during the reperfusion period.

A fish oil diet minimizes hepatic reperfusion injury in the low-flow, reflow liver perfusion model

In this study, the effects of fish oil treatment on hepatic reperfusion injury in a low-flow, reflow perfusion model were investigated. Rats were fed powdered diets containing either 5% corn or 5% encapsulated fish oil for 13 to 15 days. Average daily food intake in both control and fish oil groups was about 20 g per rat, and weight gain averaged 9 g/rat/d. Livers were perfused at flow rates around 1 muL/g/min for 75 minutes, which caused cells in pericentral regions to become anoxic because of insufficient delivery of oxygen. When normal flow rates (about 4 mL/g/min) were restored for 40 minutes, reperfusion injury occurred. Upon reflow, lactate dehydrogenase (LDH) release increased from basal levels around 1 to 50 IU/g/h in livers from control rats, whereas fish oil treatment minimized values to 16 IU/g/h Rates of bile production reached 23 muL/g/h during reperfusion in livers from controls and 38 muL/g/h in the fish oil-treated group. Oxygen uptake was about 110 mumol/g/h during the reperfusion period in livers from both groups. Malondialdehyde (MDA), an end product of lipid peroxidation, was released into the effluent perfusate at rates around 80 nmol/g/h during reperfusion in controls, and values were not affected by fish oil treatment, Portal pressure, an indicator of hepatic microcirculation, increased from basal levels of 3 to 10.5 cm H2O during reperfusion in controls, but was only elevated to 8.3 cm H2O in the fish oil-treated group. In addition, Trypan Blue distribution time, another indicator of hepatic microcirculation, was reduced significantly by 44% by fish oil treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

A fish oil diet minimizes hepatic reperfusion injury in the low-flow, reflow liver perfusion model

In this study, the effects of fish oil treatment on hepatic reperfusion injury in a low-flow, reflow perfusion model were investigated. Rats were fed powdered diets containing either 5% corn oil or 5% encapsulated fish oil for 13 to 15 days. Average daily food intake in both control and fish oil groups was about 20 g per rat, and weight gain averaged 9 g/rat/d. Livers were perfused at flow rates around 1 mL/g/min for 75 minutes, which caused cells in pericentral regions to become anoxic because of insufficient delivery of oxygen. When normal flow rates (about 4 mL/g/min) were restored for 40 minutes, reperfusion injury occurred. Upon reflow, lactate dehydrogenase (LDH) release increased from basal levels around 1 to 50 IU/g/h in livers from control rats, whereas fish oil treatment minimized values to 16 IU/g/h. Rates of bile production reached 23 μL/g/h during reperfusion in livers from controls and 38 μL/g/h in the fish oil-treated group. Oxygen uptake was about 110 μmol/g/h during the reperfusion period in livers from both groups. Malondialdehyde (MDA), an end product of lipid peroxidation, was released into the effluent perfusate at rates around 80 nmol/g/h during reperfusion in controls, and values were not affected by fish oil treatment. Portal pressure, an indicator of hepatic microcirculation, increased from basal levels of 3 to 10.5 cm H 2O during reperfusion in controls, but was only elevated to 8.3 cm H 2O in the fish oil-treated group. In addition, Trypan Blue distribution time, another indicator of hepatic microcirculation, was reduced significantly by 44% by fish oil treatment. It is concluded that fish oil minimized hepatic reperfusion injury, most likely by reducing the production of vasoconstrictive eicosanoids from arachidonic acid, thereby improving the hepatic microcirculation, which prevents cell death on reperfusion.