Effects of endothelin and nitric oxide on cardiac muscle functions in experimental septic shock model.

We aimed to investigate the possible roles of nitric oxide (NO) and endothelin on the changes of cardiac muscle function in both hyper- and hypodynamic septic shock periods. Cecal ligation and puncture was performed in 50 Wistar albino rats to induce septic shock. Changes in atrium and right ventricle papillary muscle contractions, atrium beat rate, adrenergic and cholinergic responses in these tissues were evaluated in vitro. Atrium beat rate increased in hypodynamic period (p < 0.001) that was reversed by bosentan (p < 0.001) and N(G)-nitro-L-arginine methylester (L-NAME; p < 0.05). Atrium contractions decreased in both hyper- and hypodynamic periods (p < 0.001) that were partially ameliorated by bosentan in both periods (p < 0.01) and only in hypodynamic period by L-NAME (p < 0.001). L-NAME increased papillary muscle contractions in both periods (p < 0.01), but bosentan increased it only in hyperdynamic period (p < 0.01). Bosentan and L-NAME increased potency of isoproterenol on atrium beat rate in both periods and increased carbachol potency on atrium beat rate and atrium contraction amplitude only in hypodynamic period. Bosentan increased atrium contraction response to isoproterenol in hypodynamic period (p < 0.05). Papillary muscle contraction response to isoproterenol increased in hypodynamic period (p < 0.05). L-NAME increased papillary muscle contraction response to carbachol in both periods (p < 0.01, p < 0.05, respectively). These results show that NO and endothelin may play a role in positive inotropic and negative chronotropic effects for atrium in septic shock. Bosentan and L-NAME may change potency and efficacy of isoproterenol and carbachol via upregulation of adrenergic and cholinergic receptors and/or through post receptor factors.

The role of adenosine receptors on amitriptyline-induced electrophysiological changes on rat atrium.

We investigated the role of adenosine receptors in amitriptyline-induced cardiac action potential (AP) changes in isolated rat atria. In the first group, APs were recorded after cumulative addition of amitriptyline (1 µM, 10 µM and 50 µM). In other groups, each atrium was incubated with selective adenosine A(1) antagonist (8-cyclopentyl-1,3-dipropylxanthine (DPCPX), 10(-4) M) or selective adenosine A(2a) receptor antagonist (8-(3-chlorostyryl) caffeine, 10(-5) M) before amitriptyline administration. Resting membrane potential, AP amplitude (APA), AP duration at 50% and 80% of repolarization (APD(50) and APD(80), respectively), and the maximum rise and decay slopes of AP were recorded. Amitriptyline (50 µM) prolonged the APD(50) and APD(80) (p < 0.001) and the maximum rise slope of AP was reduced by amitriptyline (p < 0.0001). Amitriptyline reduced maximum decay slope of AP only at 50 µM (p < 0.01). DPCPX significantly decreased the 50-µM amitriptyline-induced APD(50) and APD(80) prolongation (p < 0.001). DPCPX significantly prevented the effects of amitriptyline (1 µM and 50 µM) on maximum rise slope of AP (p < 0.05). DPCPX significantly prevented the amitriptyline-induced (50 µM) reduction in maximum decay slope of AP (p < 0.001). The selective adenosine A(1) receptor antagonist prevented the electrophysiological effects of amitriptyline on atrial AP. A(1) receptor stimulation may be responsible for the cardiovascular toxic effects produced by amitriptyline.

The effects of L-NG-nitroarginine in a zymosan-induced multiple organ dysfunction syndrome model.

BACKGROUND: The aim of this study was to investigate the role of nitric oxide in mesenteric ischemia, organ injury and survival in zymosan-induced multiple organ dysfunction syndrome (MODS) by using the nonselective nitric oxide synthase inhibitor L-N(G)-nitroarginine (L-NNA). METHODS: Swiss albino mice (20-40 g) were used in the study. The animals were randomly divided into four groups. The first group was treated intraperitoneally with saline and served as the sham group for L-NNA. The second group was treated with zymosan (500 mg/kg). The mice in the third and fourth group received L-NNA (20 mg/kg), 1 and 6 h after saline or zymosan administration. Six hours after the administration of zymosan, animals were used for mesenteric arterial blood flow (MABF) measurements and then sacrificed for biochemical and histopathological analyses at the 18th hour. RESULTS: In zymosan-treated animals, MABF was significantly lower than that of solvent saline-treated controls (controls: 4.7 +/- 0.8 ml.min(-1); zymosan: 1.7 +/- 0.7 ml.min(-1), p < 0.05). L-NNA did not prevent zymosan-induced MABF decrease (controls: 4.5 +/- 0.8 ml.min(-1); zymosan: 2.5 +/- 1.4 ml.min(-1), p <0.05). Also treatment with L-NNA has no beneficial effect on survival and organ injury in zymosan-induced MODS. CONCLUSION: In this study, inhibition of both inducible and constitutive nitric oxide synthase by L-NNA did not abolish the harmful effects of zymosan. L-NNA remains an agent without any therapeutic potential in this acute experimental model of MODS.

Effect of tempol, a membrane-permeable radical scavenger, on mesenteric blood flow and organ injury in a murine cecal ligation and puncture model of septic shock.

BACKGROUND: Interventions that reduce the generation or the effects of reactive oxygen species exert beneficial effects in a variety of models of septic shock. We investigated the effect of tempol, a low-molecular-weight membrane-permeable radical scavenger, on mesenteric blood flow and organ injury in a murine cecal ligation and puncture (CLP) model of septic shock. MATERIALS AND METHODS: Forty-four Swiss albino mice were anesthetized with chloral hydrate (400 mg/kg, i.p.) and subjected to CLP (except for the sham-operated animals). The animals were divided randomly into 4 groups: the 1st group was sham operated (sham-operated group, n = 10); the 2nd group underwent CLP and was injected with saline (CLP + saline group, n = 12); the 3rd group was sham operated and treated with tempol (10 mg/kg, i.p., sham-treated + tempol group, n = 10); the 4th group underwent CLP and was treated with tempol (10 mg/kg, i.p., CLP + tempol group, n = 12). Mesenteric arterial blood flow (MABF) was measured by Doppler ultrasound. Poly(adenosine 5'-diphosphate-ribose) polymerase (PARP) activity was examined in the liver, lung, and kidneys. RESULTS: In the CLP + saline group, the MABF was significantly lower than in the sham-operated group (p < 0.001). After tempol administration, MABF values significantly increased (p < 0.05). We observed significantly stronger PARP-positive staining in the lungs and kidney glomeruli in the CLP + saline group than in those of the sham-operated group (p(lung) = 0.0148, p(glomeruli) = 0.0025). A marked reduction in PARP activity was found in the lung and kidney glomeruli of the CLP + tempol group (p(lung) = 0.0026, p(glomeruli) = 0.0085). There was no significant effect of CLP on PARP activity in the liver and kidney tubuli (p(liver) > 0.05, p(tubuli) > 0.05). CONCLUSION: Tempol improved MABF in a CLP-induced septic shock model. Although tempol could not prevent the activation of PARP in the liver and kidney tubuli, it did attenuate PARP activation in the lung and kidney glomeruli.

The effect of taurine on mesenteric blood flow and organ injury in sepsis.

Endotoxin decreases mesenteric blood flow and inflicts organ injury via free radicals. We investigated whether taurine, an endogenous antioxidant and vasodilator, could attenuate the deleterious effects of endotoxin in a mouse model of sepsis. Swiss albino mice were allocated into four groups and treated either with taurine (150 mg/kg, i.p. at 0(th), 8(th), 16(th) h) or its solvent sterile saline (NaCl 0.9%, w/v) while E. coli endotoxin (20 mg/kg, i.p.) or its solvent saline were also given at 8(th) h. At 24(th) h the animals were anaesthetized and the mesenteric blood flow was measured by using perivascular ultrasonic Doppler-flowmeter. The animals were then exsanguinated, the spleen, liver, and kidneys were isolated for histopathological examination. Thiobarbituric acid-reacting substances (TBARS), glutathione, and myeloperoxidase activity were determined in the liver samples. Endotoxin significantly decreased the mesenteric blood flow and glutathione levels in liver while TBARS and myeloperoxidase activity were increased. However, taurine did not block the deleterious effects of endotoxin nor it did attenuate the histopathological injury. Therefore, we concluded that endotoxin-induced organ injury via free radicals is resistant to blockade by taurine.

The effect of nitric oxide on fentanyl and haloperidol-induced catalepsy in mice.

BACKGROUND AND OBJECTIVES: This study was designed to investigate the role of nitric oxide on catalepsy induced by fentanyl and haloperidol. METHODS: Male albino mice were treated either with fentanyl (0.1-0.2 mg kg-1, s.c.) or haloperidol (0.5-2 mg kg-1, i.p.). The non-selective nitric oxide synthase inhibitor, NG-nitro-L-arginine (10 mg kg-1, i.p.), selective neuronal nitric oxide synthase inhibitor, 7-nitroindazole (3 mg kg-1, i.p.), and nitric oxide donors, L-arginine (30-300 mg kg-1, i.p.) and D-arginine (30 mg kg-1, i.p.), were applied 20 min prior to fentanyl or haloperidol injection. A mu-opioid receptor antagonist naloxone (1 mg kg-1, i.p.) was also given in some groups. The cataleptic status of mice was assessed by placing animals in a rearing position in the cage. If the mouse maintained cataleptic posture for more than 20 s, it was scored as cataleptic and duration of catalepsy was expressed in terms of minutes. RESULTS: Both NG-nitro-L-arginine and 7-nitroindazole prolonged fentanyl-induced catalepsy (fentanyl: 3.6+/-0.8 min; fentanyl+NG-nitro-L-arginine: 77.4+/-14.6 min, fentanyl+7-nitroindazole: 56.0+/-10.4 min; n=6; P<0.01). This effect was reversed by L-arginine and naloxone, but not by D-arginine. Nitric oxide synthase inhibitors also prolonged the cataleptic action of haloperidol but to a lesser extent (haloperidol: 72.0+/-6.3 min; haloperidol+NG-nitro-L-arginine: 98.5+/-6.3 min, haloperidol+7-nitroindazole: 89.6+/-2.2 min; n=6; P<0.05). The prolongation of haloperidol-induced catalepsy with nitric oxide synthase inhibitors was not reversed by L-arginine. CONCLUSION: These results suggest a common mechanism between mu-opioid receptors and the nitric oxide system in the development of fentanyl-induced catalepsy in mice different from haloperidol-induced catalepsy.

The effect of ketamine on acute muscular ischaemia reperfusion in rats.

BACKGROUND AND OBJECTIVE: The aim of this study was to investigate any possible protective effect of ketamine in acute muscular ischaemia and reperfusion injury by measuring malondialdehyde using thiobarbituric acid assay in rats. METHODS: Twelve female Wistar albino rats were anaesthetized with chloral hydrate and randomly assigned into two groups to receive ketamine 1 mg kg(-1) min(-1) or saline infusion. Blood and gastrocnemius muscle samples were obtained 10 min after onset of infusion, before ischaemia. Then, femoral arteries were clamped for 30 min. Blood and muscle samples were obtained at the 30th minute of ischaemia and 10 min after reperfusion. RESULTS: Muscle malondialdehyde concentrations were 27.88 +/- 2.45, 27.62 +/- 3.98 before ischaemia, 32.10 +/- 4.19, 30.77 +/- 2.73 in the 30th minute of ischaemia and 44.34 +/- 2.45, 34.83 +/- 2.78 after reperfusion in saline and ketamine-treated rats, respectively (nmol g(-1), mean +/- SD). The muscle malondialdehyde level after reperfusion was lower in ketamine-treated rats compared to saline group (P < 0.002). Plasma malondialdehyde levels were 3.77 +/- 0.16, 3.78 +/- 0.18 before ischaemia, 3.81 +/- 0.25, 4.00 +/- 0.86 at the 30th minute of ischaemia and 4.00 +/- 0.53, 3.94 +/- 0.95 after reperfusion, respectively, in saline and ketamine-treated rats (micromol L(-1), mean +/- SD). The effect of ketamine on muscular malondialdehyde was not observed in concurrent plasma malondialdehyde levels. CONCLUSION: Ketamine was found to attenuate acute ischaemia-reperfusion injury in muscle tissue in rats (muscular protective). Ketamine may attenuate lipid peroxidation in muscle tissue in tourniquet-requiring manoeuvres.

The timing of endothelin and nitric oxide inhibition affects survival in a mice model of septic shock.

The effect of endothelin and nitric oxide (NO) inhibition on survival from septic shock was investigated in male Swiss albino mice (20-40 g), with particular emphasis on the timing of the administration of their blockers after Escherichia coli endotoxin (lipopolysaccharide, O55:B5, 60 mg kg(-1), i.p.) challenge. Mice were injected with the endothelin receptor antagonist bosentan (30 mg kg(-1), i.p., either 2 or 12 h after endotoxin) alone or in addition to the NO synthase blockers L-canavanine (100 mg kg(-1), i.p.), N(G)-nitro-L-arginine methyl ester (L-NAME, 3 mg kg(-1), i.p.) or aminoguanidine (15 mg kg(-1), i.p.), which were also given twice at 2 and 6 h after endotoxin. Control animals received saline, and survival rates in each group (n=10) were recorded over 24 h at 6-h intervals. At 24 h, the survival rate was 10% in controls, but 30% (n.s.) and 70% (P<0.05) in animals that received only bosentan at 2 and 12 h, respectively, indicating a relatively late involvement of endothelin in comparison to NO. In contrast, these figures were 70% (P<0.05) and 80% (P<0.05) at 12 h for L-NAME and L-canavanine, respectively, and 10% (n.s.) at 24 h, implying a relatively early involvement of NO compared to endothelin. Interestingly, survival in the aminoguanidine group (75% at 24 h, P<0.05 vs. controls) was markedly higher than that in the L-NAME and L-canavanine groups, an effect that was attributed to mechanisms other than NO inhibition. Survival was better (60%, P<0.05 vs. endotoxin alone) when bosentan was given at 2 h in combination with L-NAME, but the best outcome (90% survival, P<0.05) was observed in animals when bosentan was given at 12 h and L-NAME was injected twice at 2 and 6 h. However, the statistical analysis revealed no significant additional beneficial effect of L-NAME coadministered with bosentan. Therefore, we conclude that NO is involved during the earlier phases of septic shock in comparison to a relatively late involvement of endothelin peptides, and that bosentan alone appears to be beneficial when administered at least 12 h after the endotoxin challenge in our mice model of septic shock.

Melatonin modulates mesenteric blood flow and TNFalpha concentrations after lipopolysaccharide challenge.

OBJECTIVE: To investigate the effect of various doses of melatonin on reduction in mesenteric blood flow (MBF) and increase in tumour necrosis factor alpha (TNFalpha) concentration caused by injection of lipopolysaccharide (LPS). DESIGN: University Hospital, Turkey. SETTING: Open experimental study. ANIMALS: 59 Swiss albino mice. INTERVENTIONS: Animals were injected with melatonin solvent or 1, 10, 100, or 500 mg/kg melatonin. Ten minutes later control animals were injected with saline, and the experimental group with LPS. MAIN OUTCOME MEASURES: Mesenteric blood flow and serum TNFalpha concentration. RESULTS: In control animals, 100 and 500 mg/kg melatonin reduced MBF. LPS reduced MBF in solvent, 1, and 10 mg/kg melatonin groups. The concentration of TNFalpha was considerably increased in the mice given LPS. Melatonin reduced this response significantly. CONCLUSION: In high doses melatonin directly reduces MBF. It has no protective effect on the LPS-induced decrease in MBF. In lower doses it blocks, but at higher doses reduces, LPS-induced TNFalpha production.

Experimental study of the effect of nitric oxide inhibition on mesenteric blood flow and interleukin-10 levels with a lipopolysaccharide challenge.

The septic shock-induced decrease in mesenteric blood flow and release of proinflammatory cytokines are among the major pathophysiologic changes presumed to lead to multiple organ dysfunction syndrome (MODS). Increased nitric oxide (NO) levels are associated with both decreased mesenteric blood flow and positive modulation of proinflammatory cytokine release. In this study we aimed to determine the effect of the timing of the inhibition of nitric oxide synthase (NOS) on mesenteric blood flow and serum interleukin-10 (IL-10) concentrations during endotoxin shock. A nonspecific NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME), a specific NOS inhibitor aminoguanidine (AG), or placebo were injected 20 minutes before or 20 minutes after a lipopolysaccharide (LPS) or placebo challenge to Swiss-albino mice, as pretreatment or posttreatment, respectively. At 120 minutes after LPS or placebo injection the mesenteric blood flow was measured, and blood samples from the heart were obtained for IL-10 levels in both groups. Pretreatment and posttreatment with both NOS inhibitors prevented the LPS-induced decrease in mesenteric blood flow. Pretreatment was more effective for this purpose. Pretreatment accentuated the LPS-induced increase in serum IL-10 concentrations, whereas posttreatment had no significant effect. We conclude that the timing of NOS inhibition is important for attenuating some deleterious effects of endotoxin.

Adrenalin tolerance does not prevent bacterial translocation in a murine burn model.

Burn injury causes mesenteric vasoconstriction and bacterial translocation. Since catecholamines are powerful vasoconstrictors and elevated immediately after burn injury, we hypothesised that adrenaline tolerance might decrease burn-induced mesenteric vasoconstriction and bacterial translocation. Adrenaline tolerance was developed in Swiss albino mice. Adrenaline tolerant and control animals were subdivided into sham-burn and burn subgroups. 24 h after sham-burn or burn injury, specimens were obtained for microbiological evaluation. Also, in a separate group of adrenaline tolerant and control animals, superior mesenteric blood flow was measured. Burn injury increased bacterial translocation rate in both control (P = 0.001) and adrenaline tolerant groups (P = 0.0351). The caecal bacterial level increase was significant after burn injury in control groups (P = 0.0004) but was not significant in adrenaline tolerant animals (P = 0.743). Mesenteric blood flow was decreased significantly by burn injury in both control and adrenaline tolerant animals (P < 0.00001). The results showed that catecholamines do not mediate postburn mesenteric vasoconstriction or bacterial translocation.

Aminoguanidine attenuates endotoxin-induced mesenteric vascular hyporeactivity.

BACKGROUND: The aim of this study was to investigate the effects of inducible nitric oxide synthase inhibition by aminoguanidine on endotoxin-induced reduction in mesenteric blood flow. METHODS: Twenty Sprague-Dawley rats (180-230 g) allocated into four groups were administered either Escherichia coli endotoxin 1 mg/kg intraperitoneally or its solvent saline and were pretreated with either aminoguanidine (15 mg/kg intraperitoneally 20 min before and 2 h after endotoxin injection) or saline. Some 4 h after endotoxin injection, animals were anaesthetized, arterial blood pressure and mesenteric blood flow were measured and the resistance in the mesenteric vascular beds was then calculated. The effect of phenylephrine (1-30 microg/kg intravenously) on these parameters was also investigated. RESULTS: Endotoxin did not significantly modify the mean arterial blood pressure but decreased mesenteric blood flow by increasing the vascular resistance (mean(s.e.m.) 7.8(1.0) versus 13.7(1.2) mmHg per min per ml for control versus endotoxin groups; n = 5, P = 0.0099). Aminoguanidine alone had no effect on either the mean arterial blood pressure or mesenteric blood flow, but it completely blocked the effects of endotoxin. On the other hand, endotoxin significantly attenuated the responsiveness to phenylephrine which was restored by aminoguanidine. CONCLUSION: The present results indicate that endotoxin decreases the mesenteric vascular blood flow by increasing vascular resistance and decreases responsiveness to phenylephrine. The effects of endotoxin were inhibited by aminoguanidine. The mesenteric vasoconstriction in response to endotoxin might not be explained by the overproduction of nitric oxide; other actions of aminoguanidine may explain its inhibitory effect. Presented in part to the 10th Annual Meeting of the Surgical Infection Society - Europe, Istanbul, Turkey, May 1997

The effects of bosentan, aminoguanidine and L-canavanine on mesenteric blood flow, spleen and liver in endotoxaemic mice.

The modulatory effects of a non-selective endothelin receptor antagonist, bosentan, were investigated together with those of relatively selective inducible nitric oxide synthase inhibitors, aminoguanidine and L-canavanine, on mesenteric blood flow decrease, liver and spleen injury elicited by endotoxaemia. Swiss albino mice (20-40 g) were administered intraperitoneally bosentan (3, 10 or 30 mg kg(-1)), aminoguanidine (15 mg kg(-1)) or L-canavanine (20 or 100 mg kg(-1)) 10 min before they received saline or Escherichia coli endotoxin (10 mg kg(-1)). After 4 h, the mice were anaesthetized, mesenteric blood flow values were measured, spleen and liver weight/body weight ratios were determined and the organs were examined histopathologically. Endotoxin decreased mesenteric blood flow (ml min(-1), saline: 3.0 +/- 0.2; endotoxin: 2.2 +/- 0.2: n = 10, P < 0.05), increased the weight of liver (g per kg body weight, saline: 47.5 +/- 2.0; endotoxin: 60.8 +/- 1.9: n = 10, P < 0.05) and spleen (g per kg body weight, saline: 3.9 +/- 0.5; endotoxin: 8.6 +/- 0.9; n = 10, P < 0.01) while it inflicted significant histopathological injury to both organs. Bosentan was ineffective at 3 mg kg(-1) but at 10 and 30 mg kg(-1) doses, it abolished all the deleterious effects of endotoxin without exception. Aminoguanidine blocked most of the effects of endotoxin except those on spleen. In contrast, L-canavanine blocked only the endotoxin-induced increase in liver weight but itself increased spleen weight and failed to block any other effects of endotoxin. Thus, it can be speculated that the beneficial effects of aminoguanidine are produced largely by mechanisms other than selective inducible nitric oxide synthase inhibition since L-canavanine was not fully effective. The beneficial effects of endothelin inhibition by using bosentan in endotoxaemia can be further exploited for the understanding and the therapy of sepsis-related syndromes.

Effects of adrenaline or endotoxin tolerance states on mesenteric blood flow in endotoxaemia.

BACKGROUND: Endotoxic shock is associated with release of catecholamines as well as decreased mesenteric vascular perfusion, which is thought to cause remote organ injury. Adrenaline tolerance was reported to decrease mortality in endotoxic shock and have cross-tolerance with endotoxin tolerance. Our aim was to investigate the effect of these two tolerance conditions on the lipopolysaccharide (LPS)-induced decrease in mesenteric blood flow (MBF). METHODS: Adrenaline tolerance was developed by injecting 0.03 mg/kg adrenaline to Swiss-albino mice, gradually increasing the dose to 2 mg/kg over 5 days. Endotoxin tolerance was developed by injecting saline for 4 days and LPS 1 mg/kg at the fifth day. Control animals were injected with saline for 5 days. At 72 h after completion of injections, half of the animals in each group were challenged with saline and the other half with 20 mg/kg LPS, at 0 h. Mesenteric blood flow was measured at 4 and 24 h. RESULTS: Neither endotoxin nor adrenaline tolerance prevented an LPS-induced decrease in MBF. CONCLUSION: A low dose of LPS prior to a higher dose does not prevent an LPS-induced decrease in MBF and may actually prime for a decrease. Also, catecholamines are not primary mediators of LPS-induced decreases in MBF.

Hemodynamic monitoring of the contralateral testis during unilateral testicular torsion describes the mechanism of damage.

Contralateral testicular perfusion during unilateral testicular torsion was evaluated using simultaneous blood flow and O2 content determinations. Two groups, each consisting of 7 rats, were studied. Sham operation or 720 degrees clockwise twisting was performed on the left testes, and blood flow, O2 content and temperatures were monitored in the right testes for 180 min. An ultrasonic perivascular Doppler flowmeter system, an electronic thermometer and an O2 electrode were used for the monitoring. The contralateral testicular blood flow and relative O2 contents were stable in the control group. However, the initial and 180 min blood flow values decreased from 0.21 +/- 0.04 to 0.11 +/- 0.02 ml/min (p < 0.001), and the O2 contents from 0.857 +/- 0.123 to 0.319 +/- 0.037 (1.0 corresponds to 19.6 mm Hg pO2, p < 0.05) in the experimental group. Unilateral testicular torsion decreases the blood flow and O2 content of the contralateral testis. The contralateral testicular injury encountered following unilateral testicular torsion might result from hypoxia following the decrease in blood flow.

The effects of G-CSF treatment and starvation on bacterial translocation in hemorrhagic shock.

BACKGROUND: Bacterial translocation is thought to be responsible for infectious complications after hemorrhagic shock. The aim of this study is to investigate the effects of granulocyte colony-stimulating factor (G-CSF) treatment on bacterial translocation in starved or fed animals subjected to hemorrhagic shock. MATERIALS AND METHODS: Fifty Wistar albino rats (200-275 g) were divided into six groups such as naive control (n = 7), G-CSF treatment (n = 7), hemorrhagic shock in starved rats (n = 9), hemorrhagic shock in fed rats (n = 9), G-CSF treatment 24 h before hemorrhagic shock in starved rats (n = 9), and G-CSF treatment 20 min after hemorrhagic shock in fed rats (n = 9). Hemorrhagic shock was induced by withdrawal of 2.1 ml/100 g blood via a carotid arterial cannulae placed under sodium pentobarbital anesthesia. Twenty-four hours later, mesenteric lymph nodes, liver, spleen, and peripheral blood samples were evaluated by using a quantitative microbiological technique and the numbers of colony-forming units were compared between groups. RESULTS: No bacteria was detected in samples from naive controls or G-CSF-treated unshocked rats. In animals subjected to hemorrhage, Escherichia coli was the predominant pathogen together with Streptococcus faecalis, Pseudomonas, and Lactobacillus species. In this model, starvation augmented the magnitude of bacterial translocation while G-CSF treatment has virtually abolished it. CONCLUSION: Under experimental conditions, preshock starvation increases gut-derived bacterial translocation and administration of G-CSF before or after hemorrhagic insult significantly reduces it.

L-canavanine and dexamethasone attenuate endotoxin-induced suppression of ischaemia-reperfusion arrhythmias.

The role of inducible nitric oxide synthase in the antiarrhythmic effects of Escherichia coli endotoxin was examined in an anaesthetised rat model of myocardial ischaemia (7 min occlusion) and reperfusion (7 min) arrhythmias by using its specific blocker L-canavanine (100 mg/kg) and dexamethasone (5 mg/kg), which inhibits its expression. Endotoxin (1 mg/kg) or its solvent saline was administered intraperitoneally 4 h before the occlusion of the left coronary artery and L-canavanine or dexamethasone was administered 1 h before endotoxin or saline injection. The mean arterial blood pressure of rats receiving endotoxin was significantly lower than that of saline-treated controls, and neither L-canavanine nor dexamethasone prevented the hypotension exerted by endotoxin. However, during both the occlusion and reperfusion periods, endotoxin significantly reduced the total number of ectopic beats (e.g., during reperfusion, saline: 1177 +/- 183, n = 11; endotoxin: 248 +/- 91, n = 9; P < 0.005) and the duration of ventricular tachycardia (e.g., during occlusion, saline: 30.9 +/- 5.7 s; endotoxin: 1.8 +/- 0.9 s; P < 0.0001) while L-canavanine or dexamethasone treatment abolished the reduction exerted by endotoxin. Therefore we conclude that endotoxin possesses significant antiarrhythmic (protectant) effects in this rat model of ischaemia-reperfusion arrhythmias, and that its mechanism appears to involve the inducible nitric oxide synthase since both L-canavanine and dexamethasone inhibited this phenomenon.

Thimerosal attenuates ischaemia-reperfusion arrhythmias in rats: no modification by anti-ischaemic agent trimetazidine or endothelin receptor antagonist bosentan.

The effects of acyl-coenzyme a: lysolecithin acyltransferase (LAT) inhibitor thimerosal (20, 30 and 40 mg kg-1), anti-ischaemic and free radical scavenging drug trimetazidine (10 mg kg-1) and endothelin ETA-ETB receptor blocker bosentan [30 mg kg-1) were investigated in an anaesthetized rat model of coronary artery ligation (7 min) and release (7 min) induced myocardial ischaemia-reperfusion arrhythmias. Neither of the drugs produced significant effects on blood pressure except thimerosal which induced a transient fall lasting 5-8 min. The total number of ectopic beats during occlusion (controls 141.8 +/- 73.5, n = 12) and reperfusion (controls 1151.1 +/- 199.1, n = 10) was not modified by either trimetazidine (occlusion 452.5 +/- 128.6, n = 10; reperfusion 1002.0 +/- 198.4, n = 6) or bosentan (occlusion 431.2 +/- 112.8, n = 10; reperfusion 1530.7 +/- 296.8, n = 9) while thimerosal attenuated them (occlusion 50.2 +/- 14.9, n = 10, P < 0.01 vs controls; reperfusion 345.1 +/- 83.8, n = 8, P < 0.01 vs controls). The durations (in seconds) of ventricular tachycardia (occlusion 33.9 +/- 6.1, n = 12; reperfusion 94.2 +/- 18.1, n = 10) were also shortened by thimerosal (occlusion 2.6 +/- 1.0, n = 10, P < 0.01; reperfusion 28.5 +/- 7.8, n = 8, P < 0.01) while trimetazidine or bosentan did not significantly modify them. The incidences of ventricular fibrillation or mortality were not significantly modified by either of the drugs. Besides the lack of any effect of trimetazidine, we conclude that endogenous endothelin has no pathophysiological significance in this experimental model while LAT inhibition does.

Comparison of sodium pentobarbitone and urethane anaesthesia in a rat model of coronary artery occlusion and reperfusion arrhythmias: interaction with L-NAME.

The severity and incidences of arrhythmias induced by left coronary artery occlusion (7 min) and reperfusion (7 min) were compared in two groups of rats anaesthetized by using urethane (1.25 g kg-1, i.p.) or sodium pentobarbitone (60 mg kg-1, i.p.). A possible modification by nitric oxide synthesis blocker NG-nitro-L-arginine methyl ester (L-NAME; 20 mg kg-1, slow i.v. bolus) was also investigated. The ectopic activity observed in urethane-anaesthetized rats was less in number when compared to that of sodium pentobarbitone. The duration of ventricular tachycardia (VT) was significantly less in urethane group during the occlusion and reperfusion periods but incidence of ventricular fibrillation (VF) during the reperfusion was significantly higher. The administration of L-NAME caused a significant increase in the arterial blood pressure which disappeared after coronary artery occlusion in either anaesthesia groups. However, L-NAME had no significant effect on the difference observed between the two groups except the significant difference between total number of ectopic beats in both anaesthesia groups during occlusion was abolished by L-NAME treatment. These results suggest that, in this experimental model, the anaesthetic agent used can affect the severity of ischaemia-reperfusion arrhythmias and basal nitric oxide release does not have a major influence on them.