Participation of tumour necrosis factor and nitric oxide in the mediation of vascular dysfunction in splanchnic artery occlusion shock

1. Splanchnic artery occlusion (SAO) shock is characterized by irreversible circulatory failure. Tumour necrosis factor (TNF-alpha) may affect the L-arginine/nitric oxide (NO) pathway, thus contributing to the cardiovascular derangements of circulatory shock. 2. We investigated the contribution of both TNF-alpha and the L-arginine/nitric oxide pathway to the vascular dysfunction of SAO shock. Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the coeliac trunk for 45 min developed a severe shock state (SAO shock) resulting in a fatal outcome within 75-90 min after the release of occlusion. Sham operated animals were used as controls. SAO shocked rats had also a marked hypotension and enhanced macrophage and serum levels of TNF-alpha. Furthermore, aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE 1 nM-10 microM) and reduced responsiveness to acetylcholine (ACh 10 nM-10 microM). Endothelium-denuded aortic rings had also a marked hyporeactivity to phenylephrine, which was restored to control values by in vitro administration of NG nitro-L-arginine-methyl ester (L-NAME 10 microM). 3. In vivo administration of cloricromene (2 mg kg-1, i.v.), an inhibitor of TNF-alpha biosynthesis, increased survival, enhanced mean arterial blood pressure and reduced macrophage and serum levels of TNF-alpha. Furthermore, aortic rings from shocked rats treated with cloricromene exhibited a greater contractile response to phenylephrine and improved responsiveness to ACh when compared to aortic rings from vehicle-treated SAO shocked rats. 4. Our results suggest that TNF-alpha alters both endothelial and muscular L-arginine/nitric oxide pathways which in turn produce vascular dysfunction in SAO shock.

Contribution of intercellular adhesion molecule 1 (ICAM-1) to the pathogenesis of splanchnic artery occlusion shock in the rat

1. It has been suggested that leukocytes play a key role in the pathogenesis of splanchnic artery occlusion shock. Intercellular adhesion molecule 1 (ICAM-1) is an adhesion molecule of crucial importance in the phenomenon of leukocyte accumulation. 2. We investigated the involvement of ICAM-1 in the pathogenesis of splanchnic artery occlusion shock. Splanchnic artery occlusion (SAO) shock was induced in anaesthetized rats by clamping splanchnic arteries for 45 min. Sham-operated animals were used as controls. Survival time, serum tumour necrosis factor-alpha (TNF-alpha), white blood cell (WBC) count, mean arterial blood pressure, myeloperoxidase activity (MPO; studied as a quantitative means to assess leukocyte accumulation) and the responsiveness to acetylcholine of aortic rings were investigated. SAO shocked rats had a decreased survival time (90 +/- 9.5 min, while sham-shocked rats survived more than 4 h), reduced mean arterial blood pressure, increased serum levels of TNF-alpha (201 +/- 10 mu ml-1) and MPO activity in the ileum (0.15 +/- 0.03 mu x 10(-3) per g tissue) and in the lung (1.9 +/- 0.8 mu x 10(-3) per g tissue), leukopenia and reduced responsiveness to acetylcholine (ACh, 10 nM-10 microM) of aortic rings. 3. Administration of monoclonal antibody raised against rat ICAM-1 significantly increased survival time (225 +/- 9 min), reduced leukopenia and MPO activity both in the ileum (0.031 +/- 0.003 mu x 10(-3) per g tissue) and in the lung 0.23 +/- 0.03 mu x 10(-3) per g tissue), improved the cardiovascular changes and restored the responsiveness to ACh of aortic rings. 4. Our findings are consistent with an involvement of adhesion mechanisms in vivo in the pathogenesis of SAO shock and suggest that specific adhesion mechanisms, which support leukocyte accumulation,may represent potentially important therapeutic targets in circulatory shock.

Antibodies against intercellular adhesion molecule 1 protect against myocardial ischaemia-reperfusion injury in rat

In this study we have assayed the pathophysiological role of intercellular adhesion molecule (ICAM-1), a cytokine-inducible adhesion molecule, in a model of ischaemia reperfusion in the rat. Anaesthetized rats were subjected to occlusion (1 h) of the left main coronary artery followed by reperfusion (1 h). Sham myocardial ischaemia-reperfusion rats (Sham MI/R) were used as controls. Myocardial ischaemia plus reperfusion in untreated rats decreased survival rate, produced a marked myocardial necrosis, increased serum creatine phosphokinase activity, and cardiac myeloperoxidase activity (a marker enzyme commonly used to assess polymorphonuclear leukocyte accumulation). Furthermore, rats subjected to myocardial ischaemia-reperfusion showed an increased pressure rate index, studied as a quantitative means for assessing myocardial oxygen demand. Treatment with monoclonal anti-rat ICAM-1 (1 mg/kg i.v.), 3 h before occlusion of the left main coronary artery, significantly lowered serum creatine phosphokinase activity, blunted leukocyte accumulation and protected the myocardium from injury subsequent to ischaemia and reperfusion injury. These investigations have revealed that ICAM-1 is a critical adhesion molecule in the pathogenesis of ischaemia-reperfusion injury. In addition these results suggest that the use of monoclonal antibodies raised against ICAM-1 can represent a useful tool for the prevention of ischaemia-reperfusion damage.

TCV-309, a novel platelet activating factor antagonist, inhibits leukocyte accumulation and protects against splanchnic artery occlusion shock

The aim of this study was to evaluate: (1) the accumulation of leukocytes in the ileum and the lung during splanchnic artery occlusion (SAO) shock; (2) the role of platelet-activating factor (PAF) and tumor necrosis factor (TNF-alpha) in this phenomenon. Untreated anesthesized rats subjected to total occlusion of the celiac, superior and inferior mesenteric arteries for 45 min, followed by reperfusion, uniformly died within 90 min after reperfusion. The mean survival time was 93 +/- 7 min. The neutrophilic infiltrate was quantitated in the ileum and in the lung using a myeloperoxidase (MPO) assay. MPO activity in the ileum and in the lung averaged 0.05 +/- 0.03 and 0.4 +/- 0.02 U x 10(-3)/g protein in animals killed before occlusion. MPO activity did not change in rats killed immediately before reperfusion and was significantly elevated (0.11 +/- 0.02 and 1.7 +/- 0.6 U x 10(-3)/g protein in the ileum and the lung, respectively) in those killed 80 min after the beginning of the reperfusion. The histological examination confirmed the accumulation of leukocytes in the mucosa of the ileum and the lung over the 80 min. SAO shocked rats exhibited leukopenia and increased serum levels of TNF-alpha. In order to evaluate the role of PAF and TNF-alpha in SAO shock, a powerful PAF receptor antagonist, TCV-309 (5 micrograms/kg i.v.), was injected 5 min after reperfusion. TCV-309 increased survival time, lowered serum TNF-alpha, reduced MPO activity in both the ileum and the lung and ameliorated leukopenia induced by SAO shock.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effects of BAY U 3405, a thromboxane A2 receptor antagonist, in endotoxin shock

The present study was designed to investigate the effects of BAY U 3405, a new thromboxane A2 (TxA2) receptor antagonist, in endotoxin shock. Endotoxin shock (ES) was induced in male rats by an i.v. injection of Salmonella enteritidis lipopolysaccharide (LPS; 20 mg kg-1). LPS administration caused animal death (survival = 0%, 48 h after endotoxin challenge), systemic hypotension, depressed phagocytosis and increased blood levels of TNF-alpha, TxB2 and 6-keto-PGF1 alpha, reduced white blood cell (WBC) count (ES = 5.9 +/- 1 x 10(3) mm-3; CTRL = 13.4 +/- 5 x 10(3) mm-3) and enhanced myeloperoxidase (MPO) activity, studied as a quantitative means for assessing leukocyte accumulation, in the ileum (ES = 0.24 +/- 0.7 U g-1 fresh tissue; CTRL = 0.13 +/- 0.04 U g-1 fresh tissue), in the heart (ES = 0.41 +/- 0.1 U g-1 fresh tissue; CTRL = 0.16 +/- 0.08 U g-1 fresh tissue) and in the lung (ES = 0.68 +/- 0.11 U g-1 fresh tissue; CTRL = 0.19 +/- 0.05 U g-1 fresh tissue). Furthermore, endotoxin administration produced characteristic damage of the gastric mucosa consisting of haemmorrhagic infiltrates. BAY U 3405 (30 mg kg-1 i.v., 30 min before endotoxin challenge) increased survival rate (45% survival rate 48 h after endotoxin challenge), reduced hypotension, decreased TNF-alpha levels in serum, enhanced phagocytic activity (ES = 25.6 +/- 1.9%, BAY U 3405 = 45.9 +/- 0.4%, P < 0.001) and lowered MPO activity in the ileum (0.14 +/- 0.05 U g-1 fresh tissue), in the heart (0.18 +/- 0.08 U g-1 fresh tissue) and in the lung (0.44 +/- 0.09 U g-1 fresh tissue). Finally, the gastric alterations were significantly reduced in rats pretreated with BAY U 3405. These data suggest that this thromboxane receptor antagonist might be a useful drug in shock conditions.

Efficacy of tumor necrosis factor alpha and eicosanoid inhibitors in experimental models of neonatal sepsis

The potential role of tumor necrosis factor alpha (TNF alpha) and eicosanoids in the pathogenesis of experimental neonatal sepsis models was investigated. Lethality was induced in neonatal rats by administration of heat killed group B streptococci (GBS, 7 mg kg-1 intracardially) or Salmonella enteritidis endotoxin (0.35 mg kg-1 intracardially). The relative efficacy of six compounds with putative TNF alpha and eicosanoid inhibitory actions were tested. These were: ibuprofen (3 and 20 mg kg-1), a cyclo-oxygenase inhibitor; CGS85515 (30 mg kg-1), a lipoxygenase inhibitor; LY203647 (30 mg kg-1), a leukotriene D4 receptor antagonist; pentoxifylline (10, 50 and 100 mg kg-1), a TNF inhibitor; cloricromene (2 and 10 mg kg-1), a thromboxane A2 synthetase inhibitor with TNF alpha inhibitory actions; and SKF86002 (2.5, 5, 10 and 20 mg kg-1), a dual cyclo-oxygenase/lipoxygenase inhibitor with TNF alpha inhibitory activity. Pentoxifylline, cloricromene and SKF86002, when given intraperitoneally 2 h before challenge, produced 45, 52 and 61% reductions, respectively, in plasma levels of TNF alpha at 2.5 h post-injection with killed GBS (P < 0.05). On the contrary, pretreatment with ibuprofen, CGS85515 or LY203647 did not significantly affect TNF alpha levels. All compounds significantly attenuated the lethality by killed GBS and S. enteritidis endotoxin. These data suggest that TNF alpha and eicosanoids contribute to the pathogenesis of shock induced by killed GBS and endotoxemia.

Mediation by nitric oxide formation in the preoptic area of endotoxin and tumour necrosis factor-induced inhibition of water intake in the rat

1. Drinking was induced in rats by 24 h of water deprivation. Water intake (ml) was evaluated for a 1 h period. 2. NG-nitro-L-arginine methyl ester (L-NAME, 5-10 micrograms, i.c.v., 50-100 ng into the preoptic area (POA)), an inhibitor of nitric oxide (NO) synthase, and methylene blue (50-100 ng into POA), an inhibitor of guanylate cyclase activation, antagonized the inhibition of drinking induced by E. coli endotoxin (LPS, 640 micrograms kg-1, i.v.) and tumour necrosis factor (TNF alpha, 40 ng, i.c.v.) in 24 h water-deprived rats. 3. L-Arginine (25, 50 and 100 ng), the precursor amino acid of NO, but not the stereoisomer D-arginine (100 ng), inhibited drinking induced by water deprivation when injected into the POA 30 min before water presentation (74.4% of inhibition with the highest dose). A dose of 12.5 ng L-arginine into the POA did not exhibit antidipsogenic effects. 4. TNF alpha (20 and 40 ng, i.c.v.; 1.25, 2.5 and 5 ng into the POA) showed a dose-dependent and powerful inhibition of drinking behaviour in water-deprived rats (70.4% and 80.8%, i.c.v. and into POA, with the highest doses, respectively). A dose of 10 ng of TNF alpha given i.c.v. had no effect on the intake of water. 5. LPS and TNF alpha, given at doses (160 micrograms kg-1, i.v. and 10 ng, i.c.v., respectively) that did not influence drinking in water-deprived rats, exhibited a strong antidipsogenic effect in water-deprived rats treated with a dose of L-arginine (12.5 ng, into the POA) which did not modify drinking by itself. (LPS + L-arginine:53.6% of inhibition; TNFalpha + L-arginine: 52.0% of inhibition).6. These results suggest that NO into the POA: (1) acts as an inhibitory mechanism on thirst and (2)plays a role in the antidipsogenic effect of LPS and TNFalpha.

Central serotoninergic system involvement in the anorexia induced by NG-nitro-L-arginine, an inhibitor of nitric oxide synthase

The effects of NG-nitro-L-arginine, an inhibitor of brain nitric oxide (NO) synthase, on central serotoninergic system were studied in male obese Zucker rats and in their lean age-matched controls (FA/?; FA/FA), both groups aged 14 weeks. Acute injection of NG-nitro-L-arginine (50 mg/kg i.p.) or repeated administration of NG-nitro-L-arginine (50 mg/kg i.p. daily, for 7 days) reduced food intake and body weight in obese rats. Acute administration of NG-nitro-L-arginine reduced food intake in lean rats. However, lean rats showed tolerance to the NG-nitro-L-arginine effects after repeated administration. NG-Nitro-L-arginine administration significantly increased serotonin metabolism in the cortex, diencephalon and medulla-pons of obese Zucker rats after either acute or repeated administration of NG-nitro-L-arginine. In contrast, NG-nitro-L-arginine increased serotonin metabolism in lean rats only after acute administration, and the appearance of tolerance to NG-nitro-L-arginine anorectic effects paralleled the failure of NG-nitro-L-arginine to increase serotonin metabolism. The present data extend our previous findings indicating that NG-nitro-L-arginine possesses anorectic activity in obese Zucker rats, and clearly suggest that the central serotoninergic system mediates the anorexia induced by inhibitors of brain NO synthase.

Reduction of myocardial infarct size in rat by IRFI-048, a selective analogue of vitamin E

The effects of IRFI-048 (2,3-dihydro-5-methoxy-4,6,7-trimethyl-2-benzofuranyl acetic acid), a selective analogue of Vitamin E, on myocardial tissue injury were examined in anaesthetized rats subjected to 60-min occlusion of the left coronary artery followed by 60-min reperfusion. Infarct size (Evan's blue and tetrazolium stain), serum creatinphosphokinase (CPK), plasma malonaldehyde (MAL), cardiac myeloperoxidase (MPO) activity, and ST-segment of electrocardiogram (ECG) and survival rate were evaluated. Postischaemic reperfusion produced severe cardiac necrosis, caused neutrophil (PMNs) infiltration (evaluated by MPO activity) in the jeopardized tissue, increased serum CPK and plasma MAL, raised ST-segment of ECG, and decreased survival rate. IRFI-048, (200 and 400 mg/kg o.s.) given to the rats 6 h before occlusion, caused a reduction of necrotic area expressed as a percentage of either the area at risk or the total left ventricle, decreased MPO activity both in the area at risk (from 3.2 +/- 0.3 U x 10(-3)/g tissue to 1.1 +/- 0.4 U x 10(-3)/g tissue; p < .005) and in the necrotic area (from 5.7 +/- 0.9 U x 10(-3)/g tissue to 1.8 +/- 0.5 U x 10(-3)/g tissue; p < .001), attenuated the rise of ST-segment of ECG (from 0.51 +/- 0.14 mV in the vehicle group to 0.28 +/- 0.11 mV in the treated group; p < .005), reduced the increase of plasma MAL and serum CPK during reperfusion (from 42 +/- 5.3 nmol/ml to 15 +/- 3.1 nmol/ml and 139 +/- 13 IU/100 ml to 58 +/- 7.5 IU/100 ml, respectively; p < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of tumor necrosis factor-alpha in acute hypovolemic hemorrhagic shock in rats

Hemorrhagic shock was induced in male anesthetized rats by intermittently withdrawing blood from an iliac catheter until mean arterial blood pressure (MAP) fell and stabilized within the range of 20-30 mmHg. Survival rate, MAP, and serum and macrophage levels of tumor necrosis factor-alpha (TNF-alpha) were then evaluated. Furthermore, in ex vivo studies, the responsiveness to phenylephrine (PE; 1 nM to 10 microM) was investigated in aortic rings from hemorrhagic shocked rats. Antibodies raised against TNF-alpha (anti-TNF-alpha; 2 mg/kg) or vehicle (phosphate-buffered saline, 1 ml/kg) were injected intravenously 3 h before the bleeding. Vehicle-treated rats, subjected to hemorrhagic shock, exhibited acute and serious hypotension (MAP = 20-30 mmHg) and high levels of serum (790 +/- 47 pg/ml) and macrophage (78 +/- 9 pg/ml) TNF-alpha and died within 30 min. Moreover, aortas from shocked rats showed a marked hypocontractility to PE compared with the reactivity of aortas from a group of sham shocked rats. Anti-TNF-alpha administration significantly improved survival rate and MAP in hypovolemic shocked rats. Furthermore, the hyporesponsiveness to PE was significantly restored in aortic rings. Therefore, these data suggest that TNF-alpha is an important mediator in the pathophysiology of hypovolemic hemorrhagic shock and it might be responsible, at least in part, for the vascular hyporeactivity of this experimental circulatory shock.

Evidence for a role of platelet activating factor in hypovolemic shock in the rat

An extremely severe circulatory shock was produced in two different manners in urethane-anaesthetized rats in order to evaluate the key role of platelet-activating factor (PAF) and myocardial depressant factor (MDF) in low flow states. Haemorrhagic shock was induced by intermittently withdrawing about 50% of the estimated blood volume until mean arterial blood pressure (MAP) stabilized in the range of 20-25 mmHg. Vehicle-treated shocked rats died within 20-30 min after the last bleeding and exhibited elevated plasma activity of MDF (159.6 +/- 7.4 U/ml). Treatment with a specific PAF receptor antagonist, L-659,989, at doses of 500 or 1000 nmol/kg i.v., significantly increased survival rate, blunted the rise in plasma MDF activity and maintained MAP at higher values compared to vehicle shocked rats. Similarly, in another group of rats PAF (15 nmol/kg, i.v.) produced a shock-like state characterized by a serious hypotension in the range of 20-30 mmHg, elevated plasma MDF activity (79.7 +/- 7,7 U/ml) and death within 20-25 min after administration. L-659,989, given 5 min after the PAF-induced sharp decrease of MAP, improved survival rate, ameliorated MAP and reduced plasma levels of MDF. The results of this study, therefore, confirm that PAF plays a role in cardiovascular changes of hypovolemic circulatory shock both directly and by inducing the release of other factors such as MDF.

Protective effects of IRFI-016, a new antioxidant agent, in myocardial damage, following coronary artery occlusion and reperfusion in the rat

The new free radical scavenger IRFI-016 [2(2,3-dihydro-5-acetoxy 4,6,7-trimethyl-benzofuranyl) acetic acid] was assessed in a rat model of myocardial injury induced by 1 h of left coronary artery occlusion followed by 30 min of reperfusion. Myocardial ischaemia plus reperfusion (MI/R) produced severe cardiac necrosis, neutrophil infiltration in the jeopardized tissue, increased serum creatine kinase (CK) and ST segment of the electrocardiogram (ECG), lowered the pressure rate index (PRI), increased serum levels of tumour necrosis factor (TNF-alpha) and caused a decrease in the survival rate. Administration of IRFI-016 (100 and 200 mg/kg i.p.) 30 min before occlusion resulted in a significant protective effect in post-ischaemic reperfusion. Compared with untreated rats, IRFI-016, in particular the dose of 200 mg/kg, caused a reduction of the necrotic zone whether the necrotic area was expressed as a percentage of the area at risk (55 +/- 4% in the MI/R vehicle group and 24 +/- 2.5% in the MI/R treated group; p < 0.001) or as a percentage of the total left ventricle (23 +/- 3.4% in the MI/R vehicle group and 8 +/- 2.1% in the MI/R treated group; p < 0.005), reduced the myeloperoxidase activity, an index of neutrophil infiltration in the necrotic area (from 4.8 +/- 0.8 to 1.6 +/- 0.4 U/g tissue; p < 0.005), reduced the serum levels of TNF-alpha (from 216 +/- 13 to 45 +/- 7 U/ml; p < 0.001), blunted the rise of the ST segment of the ECG (from 0.47 +/- 0.13 mV in the vehicle group to 0.3 +/- 0.18 mV in the treated group; p < 0.001), reduced the loss of CK (from 220 +/- 15 to 88 +/- 13 IU/ml of blood; p < 0.001) and improved the depressed PRI (from 56 +/- 4% to 78 +/- 3% mm Hg/beats/min; p < 0.005). Finally, IRFI-016 significantly enhanced the survival rate evaluated at the end of the experiment. The results strongly indicate that IRFI-016 is a promising drug for cardiac ischaemia and reperfusion.

E-selectin in the pathogenesis of experimental myocardial ischemia-reperfusion injury

The role of E-selectin in the pathogenesis of an experimental model of myocardial ischemia-reperfusion injury was investigated. Pentobarbital anesthetized rats underwent left main coronary artery ligation (1 h) followed by reperfusion (1 h; MI/R). Sham operated rats were used as controls (sham MI/R). Myocardial ischemia-reperfusion injury reduced survival rate (50%), caused severe myocardial damage (necrotic area/area-at-risk 69.8 +/- 5%; necrotic area/total area = 56 +/- 7.6%), increased serum creatine phosphokinase activity (sham MI/R = 33 +/- 3 U/ml; MI/R = 215 +/- 13 U/ml), and elevated myeloperoxidase activity (investigated as an index of leukocyte adhesion and accumulation; sham MI/R = 0.11 +/- 0.02 U x 10(-3)/g tissue) in the area-at-risk (7.5 +/- 1.7 U x 10(-3)/g tissue) and in the necrotic area (7.8 +/- 2.2 U x 10(-3)/g tissue). Furthermore, MI/R rats had an increased pressure rate index, studied as a quantitative means for assessing myocardial oxygen demand. Administration of a hyperimmune serum containing antibodies against E-selectin significantly improved survival rate (80%), reduced myocardial injury (necrotic area/area-at-risk = 26.4 +/- 7%, P < 0.005; necrotic area/total area 19.1 +/- 2.8%, P < 0.005), lowered serum creatine phospokinase activity (85 +/- 5 U/ml, P < 0.001) and decreased myeloperoxidase activity in the area at risk (3.7 +/- 1.3 U x 10(-3)/g tissue, P < 0.001) and in the necrotic area (3.0 +/- 0.7 U x 10(-3)/g tissue). Finally, the administration of anti E-selectin antibodies improved the PRI in MI/R rats. The present data suggest that E-selectin in vivo plays a key role in the pathogenesis of myocardial ischemia/reperfusion injury.

Protective effects of L-659,989, a platelet-activating factor receptor antagonist, in myocardial ischemia and reperfusion in rats

The cardioprotective effects of L-659,989, a specific platelet-activating factor (PAF) receptor antagonist, were investigated in an ischemia/reperfusion model in rats. Pentobarbital-anesthetized rats were subjected to left main coronary artery occlusion (1 h) followed by reperfusion (1 h) (MI/R); Sham-operated rats were used as controls (Sham MI/R). Rats receiving vehicle showed reduced survival rate (60%), marked myocardial injury (necrotic area/total area = 54.5 +/- 6%; necrotic area/area at risk 76.6 +/- 6.7%), high serum creatine phosphokinase (CPK) activity (150 +/- 10 U/ml), and increased myocardial myeloperoxidase (MPO) activity in the area at risk (AR, 6.2 +/- 0.5 U x 10(-3)/g protein) and in the necrotic area (6.6 +/- 0.7 U x 10(-3)/g protein). PAF plasma levels increased significantly during reperfusion and peaked at 15 min of reperfusion. Administration of L-659,989 enhanced survival rate (80%), reduced myocardial damage (necrotic area/total area 25.6 +/- 3.5%; necrotic area/AR 34.6 +/- 5.4%), attenuated the increase in serum CPK (50 +/- 6 U/ml) and decreased MPO activity both in the AR (2.8 +/- 0.3 U x 10(-3)/g tissue) and in the necrotic area (2.3 +/- 0.5 U x 10(-3)/g tissue). Our results suggest that PAF-inducing adhesion and activation of polymorphonuclear leukocytes (PMN) plays a significant role in the injury associated with ischemia/reperfusion.

Food deprivation increases brain nitric oxide synthase and depresses brain serotonin levels in rats

We studied nitric oxide (NO) synthase activity and serotonin content in the diencephalon of 24 hr food deprived rats. NO synthase activity was significantly increased whereas serotonin levels together with those of tryptophan and 5-hydroxyindoleacetic acid (5-HIAA) were reduced in food deprived rats when compared to control rats. NG-Nitro-L-arginine (L-NO Arg), an inhibitor of NO synthase, was used as a tool to study the role of NO in food deprivation. Twenty-four hr food deprived male Sprague-Dawley rats were intraperitoneally (i.p.) administered L-NO Arg (12.5, 25 and 50 mg/kg) before food presentation. Control rats received a NaCl (0.9%) solution. Food consumption was monitored 1 and 2 hr after food presentation. L-NO Arg administration produced a dose-dependent reduction in food intake. Pretreatment with metergoline (2 mg/kg) but not with ritanserin (1 mg/kg) antagonized the anorectic effect of L-NO Arg. Moreover, in the diencephalon L-NO Arg significantly reduced NO synthase activity whereas it increased serotonin levels. Our data indicate that NO might have a physiological role in the regulation of food intake and suggest that brain NO may modulate the central serotoninergic system.

G619, a dual thromboxane synthase inhibitor and thromboxane A2 receptor antagonist, reduces myocardial damage and polymorphonuclear leukocyte accumulation following coronary artery occlusion and reperfusion in rats

We investigated the effect of G 619, a dual thromboxane synthase inhibitor and thromboxane A2 (TxA2) receptor antagonist, in pentobarbital-anaesthetized rats subjected to left main coronary artery ligation (1 h) followed by reperfusion (1 h; MI/R). Sham-operated rats were used as controls (sham MI/R). Survival rate, myocardial necrosis, myocardial myeloperoxidase (MPO) activity (investigated as an index of leukocyte adhesion and accumulation) and serum creatine phosphokinase (CPK) activity were studied. MI/R injury significantly reduced survival rate (45%), caused a marked myocardial necrosis, increased serum CPK activity (sham MI/R = 35 +/- 12 U/ml; MI/R = 205 +/- 13 U/ml) and produced an increase in myocardial MPO activity in the area at risk and in the necrotic area (6.3 +/- 0.5 and 6.6 +/- 0.9 U x 10(-3)/g tissue, respectively). The administration of G 619 significantly increased survival rate, lowered the area of necrosis, blunted the increase in serum CPK activity and reduced the increase in MPO activity in both the area at risk and the necrotic area. These data are consistent with an involvement of TxA2 in MI/R injury and suggest that G 619 may represent a novel therapeutic approach to the treatment of acute myocardial infarction.

Platelet activating factor interaction with tumor necrosis factor in myocardial ischaemia-reperfusion injury

The role played by platelet-activating factor (PAF) and tumor necrosis factor (TNF-alpha) in myocardial ischaemia-reperfusion injury was investigated. Pentobarbital anaesthetized rats were subjected to left main coronary artery ligation (1 h) followed by reperfusion (1 h; MI/R). Sham-operated rats were used as controls (Sham MI/R). Myocardial ischaemia-reperfusion injury produced a marked myocardial injury (necrotic area/area-at-risk = 60 +/- 5%; necrotic area/total area = 50 +/- 6%), high serum creatine phosphokinase activity (Sham MI/R = 25 +/- 10 U/ml; MI/R = 190 +/- 12 U/ml), a severe leukopenia (Sham MI/R = 10367 +/- 630 WBC x mm3; MI/R = 4123 +/- 120 WBC x mm3) and elevated myocardial myeloperoxidase activity (investigated as an index of leukocytes adhesion and accumulation) in the area-at-risk (6.2 +/- 0.5 U x 10(-3)/g tissue) and in necrotic area (6.6 +/- 0.7 U x 10(-3)/g tissue. Plasma PAF and serum TNF-alpha were significantly increased only during reperfusion. The peak of PAF plasma levels (6.5 +/- 1.2 pmol/ml) occurred earlier (15 min of reperfusion) than the peak of serum TNF-alpha (150 U/ml at 30 min of reperfusion). At the end of reperfusion, macrophage TNF-alpha was also enhanced (Sham MI/R = undetectable; MI/R = 148 +/- 12 U/ml). The administration of CV 6209, a specific PAF receptor antagonist (5 mg/kg, 5 min after occlusion), significantly reduced myocardial injury (necrotic area/area-at-risk = 27 +/- 3%, P < 0.001; necrotic area/total area = 10 +/- 2%, P < 0.001), blunted the increase in serum creatine phosphokinase (70 +/- 12 U/ml), partially restored leukopenia (8234 +/- 143 WBC x mm3) and lowered myeloperoxidase activity in area-at-risk (2.3 +/- 0.3 U x 10(-3)/g tissue; P < 0.001) and in necrotic area (2.8 +/- 0.5 U x 10(-3)/g tissue). In addition, administration of CV 6209 reduced the serum and macrophage levels of TNF-alpha. The results of this study, therefore, suggest that PAF and TNF-alpha are key mediators of myocardial ischaemia-reperfusion injury and that PAF plays a permissive role in inducing the release of other factor(s) relevant to reperfusion injury.

Reduction of myocardial leukocyte accumulation and myocardial infarct size following administration of BAY u3405, a thromboxane A2 receptor antagonist, in myocardial ischaemia-reperfusion injury

We investigated the effect of BAY u3405, a thromboxane A2 receptor antagonist in pentobarbital anaesthetized rats subjected to left main coronary artery ligation (1 h) followed by reperfusion (1 h; MI/R). Sham operated rats were used as controls (Sham MI/R). Survival rate, myocardial necrosis, myocardial myeloperoxidase activity (investigated as an index of leukocyte adhesion and accumulation) and serum creatine phosphokinase activity were studied. Ischaemia-reperfusion injury significantly reduced the survival rate (45%), caused a marked myocardial necrosis, increased serum creatine phosphokinase activity (Sham MI/R = 26 +/- 10.2 U/ml; MI/R = 213 +/- 19 U/ml) and produced a rise in myocardial myeloperoxidase activity in the area-at-risk and in the necrotic area (6.1 +/- 0.4 U x 10(-3)/g tissue and 6.7 +/- 0.9 U x 10(-3)/g of tissue, respectively). The administration of BAY u3405 (30 and 60 mg/kg/i.v., 30 min before occlusion) significantly increased survival rate, lowered the area of myocardial necrosis, blunted the increase in serum creatine phosphokinase activity and reduced the increase in myeloperoxidase activity in both the area-at-risk and the necrotic area. Furthermore, the protective effect of BAY u3405 was dose-dependent. These data are consistent with an involvement of TXA2 in myocardial ischaemia-reperfusion injury and suggest that BAY u3405 may represent a novel therapeutic approach to the treatment of acute ischaemia-reperfusion injury.

Effects of zileuton, a new 5-lipoxygenase inhibitor, in experimentally induced colitis in rats

The efficacy of zileuton, a new 5-lipoxygenase inhibitor, was investigated in comparison with sulphasalazine in an experimental model of rat colitis. Under light anaesthesia with ether, male rats were subjected to intracolonic administration of trinitrobenzene sulfonic acid (TNB) in 50% ethanol and were then sacrificed 2, 4 and 7 days after colitis induction. Untreated rats exhibited elevated colonic levels of leukotriene B4 (LTB4) and 6-keto-PGF1 alpha, and an increase in colonic myeloperoxidase (MPO) activity (investigated as an index of leukocyte adhesion and accumulation). Moreover, ulceration and inflammation of the distal colon with formation of granuloma and pathologic connections were observed. Treated rats received zileuton or sulphasalazine (50 mg/kg per os twice a day) 24 h before the induction of colitis until they were sacrificed. Treatment with the specific 5-lipoxygenase inhibitor, zileuton, resulted in significant reductions of colonic leukotriene B4 and 6-keto-PGF1 alpha synthesis, macroscopic and histological colonic damage and colonic inflammation as assessed by the measurement of MPO activity. In contrast, sulphasalazine had a lower effect than zileuton on LTB4 and MPO levels (p < 0.05), while it was able to reduce colonic damage and 6-keto-PGF1 alpha levels as well as zileuton. This study shows, therefore, that zileuton is effective in attenuating the lesions in an experimental model of colitis. Furthermore, the results are consistent with the hypothesis that leukotrienes play an important role in the pathogenesis of intestinal bowel diseases (IBD).

Tumor necrosis factor involvement in myocardial ischaemia-reperfusion injury

The role of tumor necrosis factor-alpha was investigated in an anaesthetized rat model of coronary artery ligation (60 min) and reperfusion (MI/R). Sham-occluded rats (sham MI/R) were used as controls. Survival rate, myocardial necrosis, myocardial myeloperoxidase activity, serum creatinine kinase activity and serum and macrophage tumor necrosis factor-alpha were studied. Ischaemia-reperfusion injury significantly reduced survival rate (45%), produced marked myocardial injury, increased serum creatinine kinase activity and increased myocardial myeloperoxidase activity in the area-at-risk and in the necrotic area. Serum tumor necrosis factor-alpha was undetectable during the occlusion period, but increased significantly upon release of the coronary artery. At the end of reperfusion, macrophage tumor necrosis factor-alpha was also increased. Passive immunization with a hyperimmune serum containing antibodies against murine tumor necrosis factor-alpha significantly increased survival rate (80%), lowered myocardial necrosis, reduced the increase in serum creatinine kinase activity and decreased myeloperoxidase activity in the area-at-risk and in the necrotic area. These data are consistent with an involvement of tumor necrosis factor-alpha in myocardial ischaemia-reperfusion injury.

[Evaluation of the anti-arrhythmic action of propafenone treatment and its influence on left ventricular function]

Twelve patients (9 males, 3 females, mean age 59.2 +/- 7.0 years) with hyperkinetic ventricular arrhythmias were treated for 30 days with 150 mg propafenone three times daily; the daily dosage was raised to 900 mg in non responders (< 85% reduction of ectopic ventricular beats/h). A 24-hour ECGD and mono- and bidimensional echocardiography were carried out at baseline, after 30 days on 450 mg, 30 days on 900 mg propafenone, and one week after drug withdrawal. Propafenone treatment was found to reduce significantly ectopic ventricular beats, especially with the higher dosage (44.9% reduction under 450 mg; 88.8% reduction under 900 mg). At the lower dosage, 25% of patients responded, under the higher dosage 88.9%; the latter dosage also induced a significant reduction of Lown class. Propafenone treatment was also accompanied by a reduction of maximum and mean heart rate, and by a lengthened PR interval which was almost always within the normal range, without changes of QTc. The two months of propafenone treatment did not induce significant changes of cardiac volume or left ventricular function; on the contrary, at the end of the treatment period an increase, albeit not a significant one, of the ejection fraction and a shortening of the circumference inversely proportional to the reduction in ectopic ventricular beats could be noted. In conclusion, propafenone was found to have a valid antiarrhythmic effect, especially at the 900 mg/day dosage without interfering with left ventricular function which was even found to improve under chronic treatment, probably as a result of improved compliance thanks to the reduction of ventricular ectopic beats.

Anorectic activity of NG-nitro-L-arginine, an inhibitor of brain nitric oxide synthase, in obese Zucker rats

We investigated the effects of NG-nitro-L-arginine (L-NO Arg) administration (12.5, 25 and 50 mg/kg i.p.) on food consumption and body weight of male obese Zucker rats (fa/fa) and in their lean age-matched controls (FA/?; FA/FA), both groups aged 14 weeks. Acute or repeated administration of L-NO Arg reduced food intake and body weight in both obese and lean rats. However the lean rats showed tolerance to the L-NO Arg effects after 5 days of treatment. L-NO Arg anorexia was suppressed by pretreatment with metergoline. These results suggest that L-NO Arg may represent a new anorectic drug.

Effects of intravenous administration of recombinant human erythropoietin in rats subject to hemorrhagic shock

The effects of recombinant human erythropoietin (rHuEPO) on survival and blood pressure in hypovolemic hemorrhagic shock in rats have been studied by intravenous administration. The hormone caused an increase in the time of survival compared to the group of rats without treatment (102 +/- 4.5 vs. 25 +/- 4.5 min, p < 0.01, vehicle; 102 +/- 4.5 vs. 25 +/- 2 min, p < 0.01, saline solution) and an increase in the percentage of the surviving animals (5/7 after 120 min vs. 0/7, p < 0.05). The animals treated showed an increase in mean arterial pressure that was not present in the control group. Through their data, the authors suggest the vasopressor effect of erythropoietin. Furthermore, from other studies done before, they hypothesize that the vasoactive ability of the hormone is endothelin mediated.

A new antioxidant drug limits brain damage induced by transient cerebral ischaemia

Restoration of blood flow after an ischaemic event generates the formation of oxygen radicals which could augment brain damage. The authors studied the effects of different doses (50, 100, 200 mg/kg/i.p.) of a new antioxidant, IRFI-016, [2(2,3-dihydro-5-acetoxy-4,6,7-trimethylbenzofuranyl) acetic acid] on brain damage in the Mongolian gerbil induced by 5 min of bilateral carotid occlusion (BCO) followed by reperfusion. Post-ischaemic brain malondialdehyde (MDA) levels and locomotor activity at different times and delayed neuronal death of hippocampal CA1 area on the fourth day after occlusion were evaluated. During reperfusion, after BCO, enhancement of brain MDA occurs (37.5%, 62.5% and 100% at 15, 30 and 60 min of reperfusion, respectively). Brain MDA postischaemic increases were reduced at 15 min of reperfusion to 15.4% and 44.4% by IRFI-016, 100 and 200 mg/kg, respectively. After 30 min of reperfusion brain MDA was reduced to 31.25% and 53.13% by IRFI-016 100 and 200 mg/kg, respectively. Hyperactivity and delayed neuronal death of CA1 were significantly reduced in postischaemic gerbils treated with the highest doses of IRFI-016. Results indicate that pretreatment with the antioxidant IRFI-016 improves in a dose-dependent manner brain damage induced by ischaemia and reperfusion in the gerbil.

The effect of cloricromene, a coumarine derivative, on leukocyte accumulation, myocardial necrosis and TNF-alpha production in myocardial ischaemia-reperfusion injury

The effects of cloricromene, a coumarine derivative, were studied in an anaesthetized rat model of coronary artery ligation (60 min) followed by reperfusion (60 min; MI/R). Sham operated rats were used as controls (Sham MI/R). Myocardial ischaemia-reperfusion injury produced a marked myocardial injury (necrotic area/area-at-risk = 68 +/- 4%; necrotic area/total area = 48 +/- 3%) high serum creatinphosphokinase activity (Sham MI/R = 29 +/- 8 U/ml; MI/R = 205 +/- 11 U/ml) and elevated myocardial myeloperoxidase activity (investigated as an index of leukocyte adhesion and accumulation), in the area-at-risk (6.3 +/- 0.2 U x 10(-3)/g tissue) and in necrotic area (6.5 +/- 0.5 U x 10(-3)/g tissue). Furthermore, serum TNF-alpha was undetectable during the occlusion period, but upon the release of the coronary artery significantly increased. At the end of reperfusion, macrophage TNF-alpha was also enhanced. The administration of cloricromene (2 mg/kg, 5 minutes after the onset of reperfusion) significantly reduced myocardial injury (necrotic area/area-at-risk 30 +/- 1.3%; necrotic area/total area = 25 +/- 1.5) blunted the increase in serum creatinphosphokinase activity (92 +/- 5 U/ml) and lowered myeloperoxidase activity in area-at-risk (2.5 +/- 0.2 U x 10(-3)/g tissue) and in necrotic area (2.2 +/- 0.3 U x 10(-3)/g tissue) and decreased the serum and macrophage levels of TNF-alpha. These data indicate that cloricromene exerts beneficial effects on myocardial ischaemia/reperfusion injury. Finally, since we measured increased serum levels of TNF-alpha that were blunted by the cloricromene treatment, our data are consistent with an involvement of TNF-alpha in the reperfusion injury induced by myocardial ischaemia.

Splanchnic artery occlusion shock: vinblastine-induced leukopenia reduces tumour necrosis factor and thromboxane A2 formation, and increases survival rate

This study was designed to assess the role of leukocytes in rats subjected to splanchnic artery occlusion for 45 min followed by reperfusion (SAO shock). Leukopenia was induced by an intravenous injection of vinblastine (1 mg/kg) 72 h before SAO shock. Survival rate (within 6 h), plasma levels of thromboxane B2 (TxB2), serum levels of tumour necrosis factor (TNF-alpha), and histological alteration of the intestinal tract were investigated. Control rats [white blood cells (WBC) = 10362 +/- 630/mm3] died within 2 h following ischaemia and reperfusion. Leukopenic (WBC = 1263 +/- 311/mm3) animals which underwent SAO shock survived more than 2 h and 50% of them were still alive after 6 h. Plasma TxB2 levels significantly increased in WBC count normal rats subjected to SAO shock (8.4 +/- 2.1 ng/ml), compared to sham animals (0.4 +/- 0.08 ng/ml); however SAO shock raised TxB2 levels significantly less (2.1 +/- 1.1 ng/ml) in leukopenic rats. Serum TNF-alpha, undetectable in sham-shocked rats (either with normal WBC count or without), rose up to 150 +/- 12 U/ml in shocked rate and to 45 +/- 5 U/ml (P < 0.01) in shocked animals with leukopenia. SAO shock induced a massive necrosis of the intestinal tract in rats with normal WBC count. Leukopenia prevented ileum necrosis in SAO shock. These data indicate that leukocytes play an important role in splanchnic artery occlusion and reperfusion.

[Tumor necrosis factor in myocardial ischemia and reperfusion]

The role of tumor necrosis factor (TNF-alpha) was investigated in an anaesthetized rat model of coronary artery ligation (60 min) followed by reperfusion (60 min; MI/R). Sham operated rats were used as controls (Sham MI/R). Myocardial necrosis, myocardial myeloperoxidase activity (MPO; investigated as an index of leukocyte adhesion and accumulation), serum creatinphosphokinase (CPK) activity and serum and macrophage TNF-alpha were studied. Ischemia and reperfusion produced a marked myocardial injury, with enhancement of serum CPK levels and myocardial MPO activity in the area at risk and in the necrotic area. Furthermore, serum TNF-alpha was undetectable during the occlusion period, but increased significantly after release of the coronary artery. At the end of reperfusion, macrophage TNF-alpha was also enhanced. A passive immunization with a hyperimmune serum containing antibodies against murine TNF-alpha or administration of an inhibitor of TNF-alpha synthesis, such as cloricromene, significantly lowered myocardial necrosis, reduced the increase in serum CPK and decreased MPO activity in the area at risk and in the necrotic area. Finally, the administration of the specific anti-TNF-alpha antibodies neutralized the serum levels of TNF-alpha and the injection of cloricromene reduced both serum and macrophage TNF-alpha. These data are consistent with an involvement of TNF-alpha in myocardial ischemia-reperfusion injury and suggest that drugs capable of reducing TNF-alpha might represent a novel therapeutic approach to the treatment of myocardial reperfusion injury.

Platelet activating factor interaction with tumor necrosis factor and myocardial depressant factor in splanchnic artery occlusion shock

Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the celiac trunk for 45 min, developed a severe shock state (splanchnic artery occlusion shock) resulting in a fatal outcome within 75-90 min after release of the occlusion. Shocked rats, treated with an intravenous bolus of L-659,989, a specific platelet activating factor (PAF) receptor antagonist (12.5, 25 or 50 nmol/kg, 4 min after reperfusion followed, 8 min thereafter, by a continuous infusion of 125, 250 or 500 nmol/kg for 30 min), maintained post-release mean arterial blood pressure at significantly higher values than did rats receiving the vehicle. Treatment with L-659,989 significantly increased survival rate, blunted the rise in plasma myocardial depressant factor activity and lowered serum and macrophage levels of tumor necrosis factor (TNF-alpha). In addition, the drug completely restored macrophage phagocytosis, improved macrophage killing and significantly inhibited leukopenia. To investigate the interaction between PAF, TNF-alpha and myocardial depressant factor, the blood levels of these three mediators were evaluated: shocked rats exhibited increased PAF levels with a peak at 30 min. The plasma levels of PAF peaked earlier than did either serum TNF-alpha or plasma myocardial depressant factor. Both peaks occurred 75 min after the release of occlusion. The results of this study therefore suggest that PAF is a key mediator of splanchnic artery occlusion shock and plays a permissive role in inducing the release of other factors (i.e. TNF-alpha and myocardial depressant factor) that are relevant to shock.

Evidence that nitric oxide modulates drinking behaviour

The involvement of the L-arginine-nitric oxide (NO) pathway in brain, in the regulation of drinking behaviour, has been evaluated by injecting L-arginine and N omega-nitro-L-arginine methyl ester (L-NAME) into the lateral cerebral ventricle (i.c.v.). L-Arginine (5 and 10 micrograms/rat), but not D-arginine, was antidipsogenic when administered to 24 hr water-deprived rats but did not change the intake of water in normally hydrated rats. However, L-NAME (5 and 10 micrograms/rat) did antagonize the effect of L-arginine in water-deprived animals but, by itself, did not increase thirst. L-Arginine (100 ng), when injected into the preoptic area significantly reduced water deprivation-induced drinking. The same dose was unaffective when given intraventricularly. Finally, L-arginine (5 and 10 micrograms/rat, i.c.v.) inhibited drinking induced by intraventricular injection of angiotensin II (250 ng/rat). The effect was dose-dependent. The results indicate that: (1) NO acts as an inhibitory mechanism when thirst is stimulated by water deprivation or by angiotensin II; (2) the preoptic area might be one of the central sites of antidipsogenic action of NO and (3) nitric oxide synthase might be inhibited during water deprivation.

Passive immunization with antibodies against tumor necrosis factor (TNF-alpha) protects from the lethality of splanchnic artery occlusion shock

Splanchnic artery occlusion shock was induced in anesthetized rats by clamping splanchnic arteries for 45 min. Survival rate, serum and macrophage tumor necrosis factor (TNF-alpha), peritoneal macrophage phagocytosis, and killing activities were evaluated. Shocked rats died within 2 hr, whilst all sham-shocked rats survived more than 6 hr. Serum and macrophage TNF-alpha was undetectable in sham-shocked rats while shocked rats exhibited increased serum (110 +/- 5 U/ml 90 min after release of occlusion) and macrophage levels (122 +/- 4.5 U/ml 90 min after release of occlusion) of TNF-alpha. Furthermore, splanchnic artery occlusion shock produced cardiovascular changes, reduced macrophage phagocytosis (23 +/- 4.6%) and killing (6 +/- 1.1%) activities, and induced a massive necrosis of the ileum. A passive immunization with a hyperimmune serum containing antibodies against murine TNF-alpha significantly protected rats from the lethal effects of splanchnic artery occlusion shock, lowered serum TNF-alpha (6 +/- 2.1 U/ml), and completely reverted the impairment in peritoneal macrophage phagocytosis (48 +/- 4.8%) and killing (13 +/- 1.5%) activities. In addition passive immunization had beneficial effects on the cardiovascular changes occurring during splanchnic artery occlusion shock and prevented necrosis of the ileum induced by this model of shock. By contrast, pretreatment with polymyxin B, an "antiendotoxin" antibiotic, did not modify the lethal effects and the TNF-alpha production induced by splanchnic artery occlusion shock. Furthermore, endotoxin was undetectable in the blood of splanchnic artery occlusion shocked rats. These findings are consistent with the involvement of TNF-alpha in splanchnic artery occlusion shock and suggest that the cytokine represents an important mediator of non-septic shock.

IRFI-016, a new radical scavenger, limits ischemic damage following coronary artery occlusion in rats

The effects of IRFI-016 [2(2,3 Dihydro-5-Acetoxy 4,6,7-Trimethyl-Benzofuranyl) acetic acid] a new radical scavenger were studied following six hours of myocardial ischemia, induced by left coronary artery occlusion in male rats. The loss of myocardial Creatinine Phosphokinase activity (CPK), myocardial Myeloperoxidase Activity (MPO), ECG, survival rate, and Pressure Rate Index (PRI) were evaluated in SHAM, control (vehicle i.p. injection) and IRFI-016 (200 mg/kg i.p., 30 minutes before occlusion) treated animals. CPK was significantly reduced and MPO significantly enhanced in the ischemic areas of the hearts obtained from vehicle treated rats when compared to SHAM operated ones. Pretreatment with IRFI-016 significantly attenuated (52%) loss of CPK activity in ischemic hearts and the increase in MPO activity, but did not increase PRI, thus indicating that this substance reduces the myocardial ischemic demand for oxygen. Occlusion of the coronary artery, furthermore, was associated with an immediate rise in the ST segment of the ECG, which was significantly attenuated by IRFI-016. These findings further support the important role of free radicals in the pathogenesis of acute myocardial ischemia and suggest that IRFI-016 may be a useful agent in the treatment of myocardial occlusion injury.

Evidence for a role of nitric oxide in hypovolemic hemorrhagic shock

Hypovolemic hemorrhagic shock was induced in rats by intermittently withdrawing blood from an iliac catheter for 20 min until mean arterial blood pressure (MAP) decreased to 30 mm Hg. Survival rate, survival time, plasma myocardial depressant factor (MDF) activity, MAP, and microscopic gastric alterations were then evaluated. NG-nitro-L-arginine methyl-ester (L-NAME), a selective inhibitor of nitric oxide (NO) production from L-arginine, was injected intravenously (i.v.) after the bleeding was discontinued. Untreated hemorrhagic shocked rats died in 27 +/- 3.3 min, had enhanced plasma activity of MDF, and exhibited hemorrhagic infiltrates in gastric fundus mucosa. L-NAME (5 and 10 mg/kg) significantly increased survival rate and time, blunted the increase in plasma MDF activity, and protected against the gastric lesions induced by hemorrhagic hypovolemic shock. All these protective effects were reversed by a bolus of L-arginine (30 mg/kg/i.v.), given 2 min after administration of L-NAME. Our findings suggest that NO production plays an important role in the pathophysiology of hemorrhagic shock.

Effects of captopril on the development of rat doxorubicin nephropathy

The effects of a daily administration of an anti-converting enzyme inhibitor. Captopril (CPT) (100 mg/kg/orally), on the development of functional and morphological alterations induced in rats by a single injection (7.5 mg/kg/iv) of Doxorubicin (DXR) (Adriamycin*), were investigated. Twenty-four-hour protein excretion, urine output, food intake, water intake, and body weight gain were measured weekly for 30 days. Transmission and scanning electron microscopy observations were performed on kidney samples after 30 days. Four groups were studied. Group 1 were control rats. Group 2 were rats injected with DXR. Group 3 were rats injected with DXR and treated with CPT for 30 days. Group 4 were rats injected with DXR and treated with CPT for 15 days (CPT treatment started 15 days after DXR injection). Group 1 did not show significant functional or morphological changes. Group 2 showed severe proteinuria, significant increase in urinary volume within 2 weeks, significant body weight reduction and diffuse morphological changes. These changes mainly consisted of podocyte swelling, severe foot process fusion, and presence of casts within tubular lumen. Group 3, with respect to group 2, showed a significant reduction of the 24 h protein excretion and urine output. This group displayed morphological changes similar to those observed in group 2, but with a focal distribution. Group 4 showed functional and morphological changes comparable with those of group 2. It is concluded that CPT partially inhibits the development of the functional and morphological damage induced by DXR in the rat kidney. However, CPT did not influence the natural development of nephropathy when treatment started 15 days after DXR injection.

Cloricromene, a coumarine derivative, protects against lethal endotoxin shock in rats

Endotoxin shock was induced in male rats by an intravenous (i.v.) injection of Salmonella enteriditis lipopolysaccharide (LPS; 20 mg/kg i.v.). Survival rate, macrophage and serum tumor necrosis factor (TNF-alpha), mean arterial blood pressure (MAP) and white blood cell count were then evaluated. Furthermore the in vitro effect of cloricromene on peritoneal macrophage phagocytosis and TNF-alpha release by primed peritoneal macrophages was investigated. LPS administration caused animal death (0% survival 24 h after endotoxin challenge), hypotension, marked leukopenia and increased the levels of TNF-alpha in both serum and macrophage supernatants. Cloricromene administration (0.5, 1 and 2 mg/kg i.v. 15 min after endotoxin) protected against LPS-induced lethality (100% survival rate 24 h after endotoxin challenge), reverted LPS-induced hypotension and leukopenia, and decreased TNF-alpha in both serum and macrophage supernatants. Finally, cloricromene, added in vitro to peritoneal macrophages collected from endotoxin-treated rats increased macrophage phagocytosis and reduced TNF-alpha formation by activated mononuclear phagocytes. Our data suggest that cloricromene increases survival rate in endotoxin shock through an inhibition of TNF-alpha production.

Protective effects of G 619, a dual thromboxane synthase inhibitor and thromboxane A2 receptor antagonist, in splanchnic artery occlusion shock

Splanchnic artery occlusion (SAO) shock was induced in anesthetized rats by clamping the celiac trunk and the superior mesenteric artery for 45 min. The arteries were then released and survival rate, mean survival time, mean arterial blood pressure (MAP), plasma levels of thromboxane B2 (TxB2) and 6-keto-PGF1 alpha, and the phagocytotic activity of peritoneal macrophages were evaluated. Shocked animals died within 89 +/- 10 min, while all sham-shocked rats survived greater than 3 h. SAO shock produced relevant changes in MAP, significantly increased plasma levels of TxB2 and 6-keto-PFG1 alpha, and decreased peritoneal macrophage phagocytotic activity. The administration of G 619, a dual thromboxane synthase inhibitor/thromboxane A2 receptor antagonist (50 mg/kg, 15 min before SAO shock) significantly increased survival time (190 +/- 13 min) and survival rate, reduced plasma levels of TxB2, and partially restored the impairment in peritoneal macrophage phagocytosis. Finally, the administration of G 619 had beneficial effects on changes in MAP-induced bay SAO shock. These data further confirm the involvement of TxA2 in SAO shock and suggest that G 619 may have positive effects in low-flow states.

Cloricromene antagonizes antidipsogenic effects induced by endotoxin, but not by TNF alpha, in the rat

Intravenous (640 micrograms/kg) or intracerebroventricular (0.5 and 1 microgram) injection of Escherichia coli endotoxin (LPS) causes inhibition of water intake induced by 24 hour period of water deprivation in the rat. Tumor necrosis factor alpha (TNF-alpha; 20 and 40 ng/rat) given into the lateral cerebral ventricle (i.c.v.) causes effects similar to those observed after LPS. Cloricromene, given either intravenously (1 and 2 mg/kg) or i.c.v. (250 and 500 ng), abolished the antidipsogenic effect induced by LPS (administered both i.v. and i.c.v.). Cloricromene (2 mg/kg, i.v. or 500 ng/rat, i.c.v.), on the contrary, did not modify the antidipsogenic effects induced by TNF-alpha. These data indicate that peripherally injected cloricromene (as well as that i.c.v. injected) antagonizes the effects of mediators of LPS on sites regulating thirst and suggest that cloricromene's action may be due to inhibition of brain TNF-alpha formation induced by LPS.

Protective effect of cloricromene, a coumarine derivative, in hypovolemic hemorrhagic shock in the rat

Hypovolemic hemorrhagic shock was induced in male anesthetized rats by intermittently withdrawing blood from an iliac catheter over a period of 20 min until mean arterial pressure (MAP) fell to 30 mm Hg. Survival rate, MAP, plasma myocardial depressant factor (MDF) activity and plasma levels of both TxB2 and 6-keto PGF1 alpha were then evaluated. Cloricromene (0.5, 1, and 2 mg/kg) or an equal volume of vehicle (0.9% NaCl solution) were injected intravenously 5 min after the end of the bleeding. Hemorrhagic shocked rats showed enhanced plasma levels of MDF, TxB2 and 6-keto PGF1 alpha. All vehicle-treated rats died within 25 min. Cloricromene (1 and 2 mg/kg) given curatively significantly increased survival rate and blunted the rise in plasma MDF and TxB2. Moreover, cloricromene reversed the severe hypotension and the ST-segment elevation occurring during hemorrhagic shock. The data suggest that cloricromene exerts beneficial effects in experimental hypovolemic shock, probably reversing myocardial failure.

Platelet activating factor involvement in splanchnic artery occlusion shock in rats

Splanchnic artery occlusion shock was induced in anesthetized rats by clamping the splanchnic arteries for 45 min. The survival rate, plasma levels of thromboxane B2 (TxB2) and 6-keto-PGF1 alpha, serum and peritoneal levels of macrophage tumor necrosis factor (TNF alpha), the phagocytotic and killing activity of peritoneal macrophages and white blood cells count were evaluated. Shocked rats died within 2 h, while all sham-shocked rats survived more than 6 h. Plasma TxB2 and 6-keto-PGF1 alpha levels were increased in rats subjected to splanchnic artery occlusion shock compared to the levels in sham-shocked animals. Serum and peritoneal macrophage TNF alpha levels were undetectable in sham-shocked rats, whereas shocked rats exhibited increased levels of TNF alpha. Moreover, splanchnic artery occlusion shock reduced peritoneal macrophage phagocytotic and killing activity, and also produced severe leukopenia. A specific receptor antagonist of platelet activating factor (PAF), L-652, 731 (an i.v. bolus of 3.2 mg/kg 2 min after removal of the clamps followed, 5 min thereafter, by a continuous infusion of 0.16 mg/kg per min for 30 min) significantly increased the survival rate, lowered plasma TxB2 levels and reduced both serum and macrophage TNF alpha levels in shocked rats. In addition, L-652,731 completely restored macrophage phagocytosis, partially improved macrophage killing and significantly inhibited leukopenia. Finally, the administration of L-652,731 had beneficial effects on the cardiovascular changes induced by splanchnic artery occlusion shock. These findings are consistent with the involvement of PAF in splanchnic artery occlusion shock and indicate that PAF produces shock through direct and indirect (TxB2-mediated and TNF alpha-mediated) actions.

Effects of intracerebroventricular administration of magnesium sulphate on blood pressure and heart rate in anesthetized normotensive and hypertensive rats

Intracerebroventricular (i.c.v.) injection of magnesium sulphate (MgSO4:2.5, 5 and 10 mumol in 5 microliters) decreased blood pressure and heart rate in both anesthetized normotensive (WKY) and hypertensive rats (SHR). The effects were greater in WKY than in SHR. Moreover, a pretreatment with hexamethonium (2 mg/kg, i.v.) significantly blunted the hypotensive and bradycardic effects induced by i.c.v. injection of 10 mumol of MgSO4 in both WKY and SHR. Our data suggest that MgSO4 produces hypotensive and bradycardic effects when injected i.c.v. in both WKY and SHR.