Effects Of Endotoxic Shock Research Articles

Lipoxygenase metabolites modulate vascular-derived platelet activating factor production following endotoxin challenge

Endotoxin promotes the production of potent pro-inflammatory lipid mediators, such as platelet activating factor (PAF) and eicosanoids, which contribute to the pathophysiology of endotoxic shock. Endothelial cells are both a target for and producers of these lipid mediators so it is vital to understand the pathways leading to their production in these cells. Previous research suggested a positive feedback loop between eicosanoids and PAF during endotoxemia. This study sought to determine if eicosanoids derived from the 15-lipoxygenase (15-LOX1) pathway can modulate the biosynthesis of PAF in cultured bovine aortic endothelial cells (BAEC) following endotoxin stimulation. Endotoxin stimulation increased the production of 15-LOX1-derived eicosanoids prior to PAF in primary BAEC. Exogenous addition of specific 15-LOX1 eicosanoids, as well as overexpression of 15-LOX1 in endotoxin-stimulated BAEC, further increased the endotoxin-induced production of PAF. Whereas increased expression of 15-LOX1 activity can further exacerbate endotoxin-induced PAF biosynthesis, inhibition of 15-LOX1 activity is not capable of abrogating the initial onset of endotoxin-induced PAF production. The results indicate that 15-LOX1 activity is not necessary for the initial induction of PAF following endotoxin stimulation. There may exist, however, a role for elevated 15-LOX1 activity in further escalating the extent of PAF biosynthesis in BAEC during endotoxic shock. Determining factors that can potentiate endotoxin-induced vascular dysfunction may lead to the development of novel therapeutic targets to diminish the pathophysiological effects of endotoxic shock.

Infection decreases fatty acid oxidation and nuclear hormone receptors in the diaphragm

Respiratory failure is a major cause of mortality during septic shock and is due in part to decreased ventilatory muscle contraction. Ventilatory muscles have high energy demands; fatty acid (FA) oxidation is an important source of ATP. FA oxidation is regulated by nuclear hormone receptors; studies have shown that the expression of these receptors is decreased in liver, heart, and kidney during sepsis. Here, we demonstrate that lipopolysaccharide (LPS) decreases FA oxidation and the expression of lipoprotein lipase (LPL), FA transport protein 1 (FATP-1), CD36, carnitine palmitoyltransferase beta, medium chain acyl-CoA dehydrogenase (MCAD), and acyl-CoA synthetase, key proteins required for FA uptake and oxidation, in the diaphragm. LPS also decreased mRNA levels of PPARalpha and beta/delta, RXRalpha, beta, and gamma, thyroid hormone receptor alpha and beta, and estrogen related receptor alpha (ERRalpha) and their coactivators PGC-1alpha, PGC-1beta, SRC1, SRC2, Lipin 1, and CBP. Zymosan resulted in similar changes in the diaphragm. Finally, in PPARalpha deficient mice, baseline CPT-1beta and FATP-1 levels were markedly decreased and were not further reduced by LPS suggesting that a decrease in the PPARalpha signaling pathway plays an important role in inducing some of these changes. The decrease in FA oxidation in the diaphragm may be detrimental, leading to decreased diaphragm contraction and an increased risk of respiratory failure during sepsis.

Silencing of caspase-8 and caspase-3 by RNA interference prevents vascular endothelial cell injury in mice with endotoxic shock

Septic shock and sequential multiple organ failure remain the cause of death in septic patients. Vascular endothelial cell apoptosis may play a role in the pathogenesis of the septic syndrome. Caspase-8 is presumed to be the apex of the death receptor-mediated apoptosis pathway, whereas caspase-3 belongs to the "effector" protease in the apoptosis cascade. Synthetic small interfering RNAs (siRNAs) specifically suppress gene expression by RNA interference. Therefore, we evaluated the therapeutic efficacy of caspase-8/caspase-3 siRNAs in a murine model of polymicrobial endotoxic shock. Polymicrobial endotoxic shock was induced by cecal ligation and puncture (CLP) in BALB/c mice. In vivo delivery of siRNAs was performed by using a transfection reagent (Lipofectamine 2000) at 10 h after CLP. As a negative control, animals received non-sense (scrambled) siRNA. Marked increases in caspase-8 and caspase-3 protein expression in CLP aortic tissues were strongly suppressed by treatment with caspase-8/caspase-3 siRNAs. This siRNA treatment prevented DNA ladder formation and less phosphorylation of the pro-apoptotic protein Bad seen in CLP aortic tissues. Transferase-mediated dUTP nick end labeling (TUNEL) revealed that the appearance of apoptosis in aortic endothelium after CLP was eliminated by this siRNA treatment. Although all of the control animals subjected to CLP died within 2 days, administration of caspase-8/caspase-3 siRNAs indefinitely (>7 days) improved the survival of CLP mice. Gene silencing of caspase-8 and caspase-3 with siRNAs provided profound protection against polymicrobial endotoxic shock. The prevention of vascular endothelial cell apoptosis appears to be, at least in part, responsible for their beneficial effects in endotoxic shock.

Proinsulin c-peptide exerts beneficial effects in endotoxic shock in mice

Insulin connecting peptide (c-peptide) aids the folding of proinsulin and has been considered to have little biological activity. Recently, c-peptide has been shown to improve diabetic neuropathy and nephropathy as well as vascular inflammation. In vitro studies have reported that c-peptide may activate peroxisome proliferator-activated receptor-gamma, a nuclear transcription factor that plays a regulatory role in inflammation. This study was designed to investigate the biological effects of c-peptide during endotoxemia. Prospective, randomized laboratory investigation that used an established murine model of endotoxic shock. University hospital laboratory. Mice were subjected to endotoxic shock by intraperitoneal administration of Escherichia coli lipopolysaccharide. Mice received vehicle or c-peptide (70-140 nmol/kg) intraperitoneally at 3 hrs and 6 hrs after lipopolysaccharide. Mortality was monitored for 96 hrs. In a separate experiment, mice were killed at 4, 7, and 18 hrs after lipopolysaccharide administration. Lungs and plasma were collected for biochemical assays. In vehicle-treated mice, endotoxic shock resulted in lung injury and was associated with a 41% survival rate and elevation in plasma tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, monocyte chemoattractant protein-1, and keratinocyte-derived chemokine levels. Lung nuclear levels of phosphorylated extracellular signal-regulated kinases 1 and 2 were significantly increased in vehicle-treated mice. On the other hand, lung nuclear expression and DNA binding of proliferator-activated receptor-gamma were decreased in comparison to control animals. Treatment with c-peptide (140 nmol/kg) improved survival rate (68%) and reduced plasma levels of tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1, but it did not exert hypoglycemic effects. Treatment with c-peptide also up-regulated lung nuclear expression and DNA binding of proliferator-activated receptor-gamma and reduced phosphorylation of extracellular signal-regulated kinases 1 and 2 in comparison to vehicle-treated mice. Our data show that c-peptide has beneficial effects in endotoxic shock, and this therapeutic effect is associated with activation of proliferator-activated receptor-gamma.

Different effects of endotoxic shock on the respiratory function of liver and heart mitochondria in rats

This study was designed to clarify whether mitochondrial function/dysfunction and reactive oxygen species (ROS) production have a temporal relationship with organ failure during endotoxic shock. Adult male Sprague-Dawley rats were divided into three groups receiving 1) isotonic saline (control group, n = 16); 2) 8 mg/kg lipopolysaccharide (LPS; n = 8); or 3) 20 mg/kg LPS (n = 8) intraperitoneally under short anesthesia with 3.5% of isoflurane. After 16 h, animals were killed to analyze plasma, rat liver mitochondria (RLM), and rat heart mitochondria (RHM). In accordance with plasma analysis, LPS-treated rats were divided into "responders" and "nonresponders" with high and low levels of alanine aminotransferase and creatine, respectively. RHM from responders had significantly lower respiratory activity in state 3, suggesting a decreased rate of ATP synthesis. In contrast, RLM from responders had significantly higher respiratory activity in state 3 than both nonresponders and the control group. This increase was accompanied by a decrease in phosphate-to-oxygen ratio values, which was not observed in RHM. ROS generation determined with a spin probe, 1-hydroxy-3-carboxypyrrolidine, neither revealed a difference in RHM between LPS and control groups nor between responders and nonresponders. In contrast, RLM isolated from responders showed a marked increase in ROS production compared with both the control group and nonresponders. Our data demonstrate that 1) RHM and RLM respond to endotoxic shock in a different manner, decreasing and increasing respiratory activity, respectively, and 2) there is a temporal relationship between ROS production in RLM (but not in RHM) and tissue damage in rats subjected to LPS shock.

The effects of dexamethasone on rat brain cortical nuclear factor kappa B (NF-κB) in endotoxic shock

To explore the molecular mechanism of brain tissue injury induced by lipopolysaccharide (LPS), we studied the effects of endotoxic shock on rat brain cortex NF-kappaB and the effects of dexamethasone on these changes. Rats were randomly divided into LPS, LPS + dexamethasone, and control groups. The DNA-binding activity of NF-kappaB was observed using electrophoretic mobility shift assay (EMSA). Protein expression in nuclear extracts was studied using Western blots, and nuclear translocation was observed using immunohistochemistry. These indices were assayed at 1 h and 4 h after intravenous injection of LPS (4 mg x kg(-1)). EMSA showed significantly increased NF-kappaB DNA-binding activity in nuclear extracts from the LPS group at both 1 h and 4 h after LPS injection, compared with the control group (P < 0.01). For the LPS group, the NF-kappaB DNA-binding activity was greater at 1 h than at 4 h (P < 0.05). The expression of p65 and p50 protein in the nuclear extracts was also increased, as compared with the control group. However, the expression of p65 and p50 protein from cytosolic extracts did not show any significant change. Dexamethasone down-regulated not only NF-kappaB DNA-binding activity but also the expression of p65 protein in the nuclear extracts. From these data, we have concluded that NF-kappaB activation and nuclear translocation of NF-kappaB play a key role in the molecular mechanism of brain tissue injury in endotoxic shock. Dexamethasone may alleviate brain injury by inhibiting NF-kappaB activation.

Evaluation of Fructose 1,6 diphosphate for Salvage of Ischemic Gracilis Flaps in Rats

Fructose 1, 6 diphosphate (FDP), a metabolic intermediate, provides an alternative mechanism to circumvent the rate-limiting step in the Kreb's cycle. This agent has been observed to prevent the effects of ischemia on heart tissue and kidney function and the effects of endotoxic shock. It has been shown conclusively to minimize the adverse effects of ischemia-reperfusion injury in experimental pedicled skin flaps in animals. The present study was done to evaluate the effect of intra-arterial administration of FDP on salvage of ischemic microvascular transfer of gracilis muscle flaps in rats, with the premise that it might prolong the ischemia time of muscle flaps at room temperature, thus increasing chances of flap survival. Irrigation with FDP did not change the quantitative survival of the flaps, but there was qualitative improvement on histologic evaluation and DNA analysis. Decreased inflammatory damage and DNA fragmentation were seen at the 2.5-hr period. Histologic staining for mitochondrial oxygenation in gracilis muscle also showed increased uptake in the FDP-treated group vs. control at the 2.5-hr ischemia period. Further experiments with different modes of FDP administration should be carried out to identify more effective means of amelioration of flap ischemia.

Effects of endotoxic shock on neuronal NOS and calcium transients in rat cardiac myocytes

Objective: The effects of endotoxic shock on transcriptional and translational pattern of nitric oxide synthase isoforms (NOSs) and cytoplasmic calcium were investigated. Methods: Male SD rats injected with lipopolysaccharides or saline were sacrificed after 6 and 20 h. Cardiac myocytes were enzimatically isolated from the excised hearts and evaluated for: (1) expression of constitutive (e and n) and inducible (i) NOSs by RT-PCR; (2) NOSs protein levels by Western blot, enzymatic activities by a radioimmunometric assay and nitric oxide metabolites by spectrophotometry; (3) calcium transients by Indo-1 fluorescence. Results: Increase in iNOS mRNA, and decrease in e and nNOS mRNAs were observed in cardiac myocytes isolated 6 h after LPS injection with recovery to basal levels at 20 h. Significant down-regulation of e and nNOS protein levels ( p < 0.01) and calcium-dependent activity ( p < 0.05) were detected at 20 h. Serum TNF-α increased after 6 and 20 h ( p < 0.05), whereas NO metabolites rose only after 20 h ( p < 0.0001). The diastolic calcium increased 6 h from LPS injection ( p < 0.0001) and remained significantly higher after 20 h. Calcium transients amplitude was not affected by LPS injection. Conclusions: Endotoxic shock stimulates iNOS and down-regulates expression of nNOS in purified cardiac myocytes, but endogenous NO production does not likely affect calcium transients.

Effect of anthocyanins contained in a blackberry extract on the circulatory failure and multiple organ dysfunction caused by endotoxin in the rat.

Anthocyanins are a group of naturally occurring phenolic compounds related to the colouring of plants, flowers and fruits. These pigments are important as quality indicators, chemotaxonomic markers and for their antioxidant activities. Here we have investigated the therapeutic efficacy of anthocyanins contained in a blackberry extract on (i) circulatory failure, (ii), multiple organ dysfunction and (iii) activity of the inducible isoforms of nitric oxide (NO) synthase (iNOS) and cyclooxygenase (COX-2) in anaesthetised rats with endotoxic shock. In a model of endotoxic shock induced by lipopolysaccharide (LPS, E. coli, 10 mg/kg, i.v.) in the rat, pretreatment with anthocyanins present in the blackberry extract (5 mg/kg, i. v. 30 min before LPS) prevented the hypotension induced by LPS. Endotoxaemia also caused rises in the serum levels of (i) glutamyl oxaloacetic transaminase (GOT), glutamyl pyruvic transaminase (GPT), alkaline phosphates and bilirubin (hepatic dysfunction) (ii) creatinine (renal dysfunction), (iii) amylase and lipase (pancreatic injury), (iii) NOx and 6-keto-PGF1 alpha. Anthocyanins attenuated the hepatic and pancreatic injury, the renal dysfunction and decreased NOx and 6-keto-PGF1 alpha levels. Endotoxaemia for 6 h resulted in a substantial increase in iNOS and COX activity in rat lung, which was attenuated in rats pretreated with anthocyanins. Moreover, anthocyanins (0.02 - 0.32 mg/mL) inhibited in vitro iNOS and COX activity from lung of LPS-treated rats. Polymorphonuclear (PMN) infiltration (myeloperoxidase activity), lipid peroxidation (malondialdehyde levels), as well as tissue injury (histological examination) induced by LPS in rat lung and ileum was reduced by anthocyanins (5 mg/kg, i. v. 30 min before LPS). Furthermore, endotoxaemia induced the formation of nitrotyrosine and poly(ADP-ribose) synthetase (PARS) activation as determined by immunohistochemical analysis of lung and ileum tissues. The degree of staining was lowered by anthocyanin treatment. These results indicate that the anthocyanins contained in the blackberry extract exert multiple protective effects in endotoxic shock.

Effects of endotoxic shock on right ventricular systolic function and mechanical efficiency.

To investigate the effects of endotoxin infusion on right ventricular (RV) systolic function and mechanical efficiency. Six anesthetized pigs (Endo group) received a 0.5 mg/kg endotoxin infusion over 30 min and were compared with six other anesthetized pigs (Control group) receiving placebo for 5 h. RV pressure-volume (PV) loops were obtained by the conductance catheter technique and pulmonary artery flow and pressure were measured with high-fidelity transducers. RV adaptation to increased afterload during the early phase of endotoxin-induced pulmonary hypertension (T30) was obtained by both homeometric and hetereometric regulations: the slope of the end-systolic PV relationship of the right ventricle increased from 1.4+/-0.2 mmHg/ml to 2.9+/-0.4 mmHg/ml (P<0.05) and RV end-diastolic volume increased from 56+/-6 ml to 64+/-11 ml (P<0.05). Consequently, right ventricular-vascular coupling was maintained at a maximum efficiency. Ninety minutes later (T120), facing the same increased afterload, the right ventricle failed to maintain its contractility to such an elevated level and, as a consequence, right ventricular-vascular uncoupling occurred. PV loop area, which is known to be highly correlated with oxygen myocardial consumption, increased from 1154+/-127 mmHg/ml (T0) to 1798+/-122 mmHg/ml (T180) (P<0.05) while RV mechanical efficiency decreased from 63+/-2% (T0) to 45+/-5% (T270) (P<0.05). In the very early phase of endotoxinic shock, right ventricular-vascular coupling is preserved by an increase in RV contractility. Later, myocardial oxygen consumption and energetic cost of RV contractility are increased, as evidenced by the decrease in RV efficiency, and right ventricular-vascular uncoupling occurs. Therefore, therapies aiming at restoring right ventricular-vascular coupling in endotoxic shock should attempt to increase RV contractility and to decrease RV afterload but also to preserve RV mechanical efficiency.

Inhibition of tumour necrosis factor and reversal of endotoxin-induced shock by U-83836E, a 'second generation' lazaroid in rats.

1. Antioxidants can exert protective effects in endotoxic shock by either a reduction of the oxidant damage or attenuation of Tumour Necrosis Factor (TNF-alpha) production. 2. Lazaroids are a family of compounds that inhibit lipid peroxidation. Besides, they can also reduce TNF-alpha. U-83836E is a new lazaroid lacking the glucocorticoid ring. 3. Aim of our study was to investigate the effect of U-83836E on TNF-alpha production either in vivo or in vitro. Endotoxic shock was produced in male rats by a single intravenous (i.v.) injection of 20 mg kg(-1) of S. enteritidis lipopolysaccharide (LPS). LPS administration reduced survival rate (0% survival, 72 h after endotoxin administration), decreased mean arterial blood pressure, increased serum and macrophage TNF-alpha and enhanced plasma malonylaldehyde (MAL) levels. Furthermore aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE 1 nM-10 microM). 4. Treatment with U-83836E (7.5, 15 and 30 mg kg(-1), i.v.) 5 min after endotoxin challenge significantly protected against LPS induced lethality (90% survival rate and 80% survival rate 24 h and 72 h after LPS injection respectively, following the highest dose of the drug), reduced hypotension, blunted plasma MAL, decreased serum and macrophage TNF-alpha and restored the hyporeactivity of aortic rings to control values. In vitro LPS stimulation (50 microg ml(-1) for 4 h) significantly increased cytokine production in macrophages (Mphi) harvested from untreated normal rats. Pretreatment with pertussis toxin (PT; 0.1, 1 and 10 ng ml(-1) 4 h before LPS) significantly increased TNF-alpha production. PT effects on these LPS responses were correlated with a PT mediated ADP ribosylation of a 41 kDa protein. U-83836E (50 microM) reduced, in a dose dependent manner, LPS induced TNF-alpha production and inhibited the PT effects on cytokine production and on ADP ribosylation of the protein. 5. Our data suggest that lazaroids may affect the early events associated with LPS receptor mediated activation of a G protein in LPS induced TNF-alpha production. These molecular events may explain, at least in part, the in vivo inhibition of cytokine production and reversal of endotoxic shock.

Effects of endotoxic shock in several functions of murine peritoneal macrophages.

Gram negative sepsis and septic shock continue to be a major medical problem, with a complex physiopathology and it is associated with high mortality. Although secretion of cytokines such as tumor necrosis factor-alpha by macrophages is the principal host mediator of septic shock, other characteristic functions of macrophages implicated in their phagocytic capacity have not been studied in the process of endotoxic shock. In the present study we have used an intraperitoneal injection of E. coli lipopolysaccharide (LPS) (100 mg/kg) in order to obtain an endotoxic shock model in adult female BALB/c mice. Peritoneal cell suspensions were obtained at several times (2, 4, 12 or 24 h) after injection and the following functions were studied on the peritoneal macrophages: adherence to substrate, mobility (spontaneous and directed or chemotaxis), ingestion of particles and superoxide anion production. The results showed a stimulation of adherence, ingestion and superoxide production as well as a decrease of chemotaxis in the animals injected with LPS. These effects changed with time after LPS injection. Thus, the increase of adherence and the decrease of mobility were higher during the first hours, whereas the increase in ingestion and superoxide production turned larger with time.

Effects of endotoxic shock on diaphragmatic function in mechanically ventilated rats.

Diaphragmatic function was investigated in mechanically ventilated rats during endotoxic shock (group E, n = 18) and after saline solution injection (group C, n = 8). Endotoxic shock was produced by a 1-min injection of Escherichia coli endotoxin (10 mg/kg iv) suspended in saline. Diaphragmatic strength was assessed before (T0) and 15 (T15) and 60 (T60) min after injection by measuring transdiaphragmatic pressure (Pdi) generated during bilateral phrenic stimulation at 0.5, 10, 20, 30, 50, and 100 Hz. Diaphragmatic neuromuscular transmission was assessed by measuring the integrated electrical activity of the diaphragm. Diaphragmatic endurance was assessed 75 min after injection from the rate of Pdi decline after a 30-s continuous 10-Hz phrenic stimulation. In 16 additional animals, diaphragmatic glycogen content was determined 60 min after inoculation with endotoxin (n = 8) or 0.9% sodium chloride solution (n = 8). Diaphragmatic resting membrane potential (Em) was measured in 16 additional animals 60 min after endotoxin (n = 8) or saline injection (n = 8). Mean blood pressure decreased from 74 +/- 3 to 53 +/- 6 mmHg at T60 in group E, whereas it was maintained in group C. At T60 Pdi was decreased in group E for frequencies of 50 and 100 Hz and was associated with a decreased diaphragmatic electromyographic activity of 25.3 +/- 2.5 and 26.5 +/- 5.2% for 50- and 100-Hz stimulations, respectively, in comparison with T0 values.(ABSTRACT TRUNCATED AT 250 WORDS)

Beneficial effects of prostaglandin E 2 in endotoxic shock are unrelated to effects on PAF-acether synthesis

The effects of endotoxic shock on the synthesis of PAF-acether by the stomach, duodenum and lung were examined in the rat. Furthermore, the effect of pretreatment with prostaglandin E 2 on endotoxin induced PAF-acether synthesis and changes in vascular permeability were examined. Administration of endotoxin resulted in significant increases in PAF-acether synthesis in all tissues studied. Such increases were apparent within 5–15 minutes of the administration of endotoxin, corresponding to the time when significant hypotension, hemoconcentration and increases in gastrointestinal vascular permeability were first observed. Pretreatment with prostaglandin E 2 resulted in a significant reduction of endotoxin-induced hypotension, hemoconcentration and changes in vascular permeability in the gastrointestinal tract. However, prostaglandin pretreatment did not significantly alter endotoxin-induced PAF-acether release from the gastrointestinal tissues studied. These results demonstrate that prostaglandin E 2 can significantly attenuate several of the systemic and gastrointestinal manifestations of endotoxic shock. The mechanism responsible for these beneficial actions appears to be unrelated to effects of prostaglandin E 2 on PAF-acether synthesis.

Effects of drugs on the pyrogenicity of toxic shock syndrome toxin 1 and its capacity to enhance susceptibility to the lethal effects of endotoxic shock in rabbits.

The effects of various kinds of drugs on the pyrogenicity of toxic shock syndrome toxin 1 (TSST-1) and its capacity to enhance the lethal effects of endotoxin in rabbits were studied. Antipyretic agents--including aspirin, aminopyrine, and indomethacin--that were given immediately or 2 hours after injection of TSST-1 decreased the febrile response to TSST-1 but did not inhibit the enhancement of lethality. Cyclosporine, which was given 2 hours after injection of TSST-1, suppressed the fever but did not inhibit the lethal effects. Methylprednisolone given immediately or 2 hours after TSST-1 injection did not decrease the fever but inhibited the lethal effect. Of the agents phentolamine, dopamine, and chlorpromazine, which are reported to suppress endotoxic shock experimentally, only chlorpromazine decreased the fever, and none inhibited the lethal effects.

Effect of endotoxic shock on skeletal muscle intracellular electrolytes and amino acid transport.

Soleus muscle intracellular electrolytes and alpha-aminoisobutyric acid (AIB) uptake and its regulation by insulin were investigated during endotoxic shock in vivo. Fasted rats (90 g) were injected with [14C]AIB (1-10 mg/kg, iv) and Salmonella enteritidis endotoxin (20 mg/kg, iv) or saline and killed 1-5 h later. AIB uptake into muscle was corrected for uptake into extracellular space (measured as insulin distribution in muscle in vivo) and expressed as [AIB]/[AIB] ratios to assess active transport. The maximum level of active AIB cell transport by extracellular endotoxic muscles [3.3 +/- 0.2 (SE)] was lower than control muscles (4.9 +/- 0.3) at the time when plasma insulin concentration in endotoxic rats (16.8 +/- 2.0 uU/ml) was greater than controls (7.9 +/- 1.7 uU/ml). Insulin-stimulated AIB transport was significantly lower in endotoxic muscles (from a basal value of 3.3 +/- 0.2 to 4.4 +/- 0.5, 5.0 +/- 0.3, and 4.9 +/- 0.3 at 125, 250, and 500 mU/kg intravenous insulin, respectively) than in control muscles (from 4.9 +/- 0.3 to 5.7 +/- 0.2, 8.0 +/- 0.4, and 10.8 +/- 0.8). The intracellular electrolyte concentrations in endotoxic soleus muscles ([Na] = 15.87 +/- 0.9, [K] = 145 +/- 1.7, [Cl] = 14.61 +/- 0.9) were substantially altered when compared with control muscles ([Na] = 9.33 +/- 1.1, [K] = 164 +/- 1.5, [Cl] = 4.1 +/- 0.6) 5 h postinjection. The membrane potential, estimated from chloride equilibrium potential was lower in endotoxic muscles (-52.7 +/- 1.6 mV) when compared with control muscles (-89 +/- 3.5 mV).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of endotoxic shock on kinetics of system A amino acid transport in rat soleus muscle.

This study evaluated the kinetics of system A amino acid transport in soleus muscle during endotoxic shock. Fasted male rats (80-100 g) were killed by decapitation 5 h after the intravenous injection of saline (control) or 20 mg/kg Salmonella enteritidis endotoxin. Soleus muscles (40 mg) from control or endotoxic rats were incubated in oxygenated Krebs-Ringer-bicarbonate buffer (pH 7.4) at 37 degrees C for 20, 40, or 60 min. Initial rates of entry of alpha-aminoisobutyric acid (AIB) into the inulin-inaccessible space of muscles were measured over a wide range of AIB concentrations (0.1-20.0 mM). Initial rates of AIB transport were separated into two parallel transport processes, a saturable carrier-mediated component and a nonsaturable passive diffusive process. The diffusion constant for the nonsaturable process in the endotoxic muscles (0.36 h-1) was 38% greater than control muscles (0.26 h-1). The maximum rate of AIB transport decreased from 55.6 +/- 3.3 nmol . g dry wt-1 . min-1 in controls to 18.3 +/- 1.9 nmol . g dry wt-1 . min-1 in endotoxic muscles. The apparent Km for saturable AIB transport was not different between control (1.68 +/- 0.12 mM) and endotoxic muscles (1.64 +/- 0.19 mM). Alterations of system A amino acid transport in endotoxic soleus muscles were due to an increase in passive AIB diffusion and a decrease in the number and/or activity of existing carriers and not to a change in carrier affinity for AIB. These results elucidate the mechanism for the decreased amino acid transport (system A) by soleus muscle in endotoxic shock.

Respiratory muscle fatigue: a cause of ventilatory failure in septic shock.

The effect of endotoxic shock on the respiratory muscle performance was studied in spontaneously breathing dogs given Escherichia coli endotoxin (Difco Laboratories, 10 mg/kg). Diaphragmatic (Edi) and parasternal intercostal (Eic) electromyograms were recorded using fishhook electrodes. The recorded signals were then rectified and electrically integrated. Pleural, abdominal, and transdiaphragmatic (Pdi) pressures were recorded by a balloon-catheter system. After a short control period, the endotoxin was administered slowly intravenously (within 5 min). Death was secondary to respiratory arrest in all animals. All animals died within 150-270 min after the onset of endotoxic shock. Within 45-80 min of the endotoxin administration, mean blood pressure and cardiac output dropped to 42.1 +/- 4.1 and 40.1 +/- 6.0% (mean +/- SE) of control values, respectively, with little change afterward. Mean inspiratory flow rate and Pdi increased from control values of 0.27 +/- 0.03 l X s-1 and 5.75 +/- 0.7 cmH2O to mean values of 0.44 +/- 0.3 l X s-1 and 8.70 +/- 1.05 cmH2O and then decreased to 0.17 +/- 0.03 l X s-1 and 3.90 +/- 0.30 cmH2O before the death of the animals. There were no major changes in the mechanics of the respiratory system. Edi and Eic increased progressively to mean values of 360 +/- 21 and 263 +/- 22% of control, respectively, before the death of the animals. None of the dogs were hypoxic. Arterial PCO2 decreased from a control value of 42.9 +/- 1.7 Torr to a mean value of 29.9 +/- 2.8 Torr and then increased to 51 +/- 4.3 Torr before the death of the animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Naloxazone lacks therapeutic effects in endotoxic shock yet blocks the effects of naloxone

Cardiovascular effects of the high affinity, irreversible opiate antagonist, naloxazone, were investigated in conscious rats subjected to endotoxic shock. Unlike other less selective opiate antagonists such as naloxone, naloxozone failed to block or reverse the hemodynamic effects of endotoxemia. However, naloxazone pretreatment prevented the usual therapeutic effects of naloxone in endotoxic shock. Results indicate that high affinity ( μ 1-site) opiate binding is not involved in the pathophysiological actions of endogenous opiates in shock, and suggest that interactions among opioid receptor subtypes may occur in vivo.

Shock-induced changes in the sodiumpotassium adenosine triphosphatase enzyme system in dog hearts

The effects of endotoxic shock on the partial reaction of the (Na + + K +)-ATPase enzyme system, K +-activated para-nitrophenylphosphatase (K +-PNPPase), and on ouabain binding were studied in isolated adult dog heart myocytes. Results obtained 4 hr after endotoxin administration showed that the kinetic parameters of K +-PNPPase such as V max and K m for K + activation, and V max, S 0.5, and the Hill coefficient for Mg 2+ and para-nitrophenylphosphate saturation were not altered. However, the sensitivity of K +-PNPPase to ouabain inhibition was decreased markedly; the I 50 value for ouabain inhibition was increased from the control value of 0.39 μ M to 2.2 μ M in endotoxic shock. Results obtained from ouabain binding studies indicated that the K d for high-affinity binding was increased by 36% with no change in the K d for low-affinity binding and no change in the total number of binding sites. The average affinity for ouabain binding at low fractional occupancy of receptor sites was markedly decreased. The effect of ouabain on K +-PNPPase activity was changed from inhibition to activation when less than 32% of the receptor sites were occupied. These data indicate that 4 hr after endotoxin administration, the total number of ouabain receptor sites and the dephosphorylation process of the enzyme cycle were not altered, but the coordination of the ouabain receptor subunit and the catalytic subunit of the enzyme system was impaired. Based on these results, it is concluded that the therapeutic value of cardiac glycosides as a means of improving myocardial contractility during endotoxic shock should be reevaluated.