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PubMed1991

Role of prostaglandin-mediated mechanisms during experimentally induced endotoxin fever in the lactating goat.

The effects of endotoxin (LPS) on the cortisol, glucose, NEFA (non-esterified fatty acids), STH (somatotropin) and oxytocin levels in plasma of goats are described. The changes in plasma cortisol, STH and NEFA, as well as in RT (rectal temperature) were compared after i.v. and i.mam. administration of endotoxin. The other parameters, glucose and oxytocin, were followed only after i.v. endotoxin administration. The observed metabolic and hormonal alterations in plasma were also studied after pretreating the goats with the non-steroidal anti-inflammatory and antipyretic drug flurbiprofen in order to evaluate the possible involvement of prostaglandin in these phenomena. After i.v. administration of LPS a biphasic temperature curve for the highest dose of LPS with peak maxima at 1h and 4h after LPS challenge, was observed. Intramammary administration of endotoxin induces a monophasic fever response, with a latency time of approximately 3h, and peak values after 6h. The onset of the fever response in the i.v. experiments coincided with the oxytocin maximum and with early hyperglycemia. Intravenous endotoxin in goats also induces an increase in plasma NEFA, cortisol and STH. The early increase in NEFA, with a maximum after 2h and occurring before the fever peak, is followed by a significant rise in cortisol with peak effects after 3 h. The increase in plasma STH coincided with the decrease in plasma NEFA returning to control levels again. Peak concentrations in plasma STH occurred after 4 h. All the changes observed after the i.v. administration of endotoxin are dose-dependent. Pretreating goats with flurbiprofen completely abolished fever response, as well as the early hyperglycemia and the oxytocin release to i.v. LPS, indicating that these changes were prostaglandin-mediated and might be a reflexion of an activation of the sympathetic adrenomedullary system. The LPS-induced changes in plasma cortisol, NEFA and STH are only partly depressed and delayed by flurbiprofen. The residual hormonal responses to high doses of endotoxin suggest that an additional direct action of circulating endotoxins on the hypothalamus cannot be excluded. Intramammary LPS administration in goats only induced a very weak increase in plasma cortisol. The complex interplay of hormones and metabolic substances in the homeostasis of the inflammation reaction is discussed.

Animals↗
PubMed1990

Effect of bacterial endotoxin on placentation of rats.

The effect of bacterial endotoxin on placentation in rats was studied on 160 CFY pregnant rats. Based on this experiment, it was concluded that (i) the endotoxin (1 mg/animal i.p.) inhibited placentation (in 90% of animal). (ii) The endotoxin-induced fetopathy almost exclusively resulted in abortion. (iii) The fetuses reacted to endotoxin with relatively the same degrees of susceptibility. (iv) The growth of surviving fetuses seemed to be undisturbed. (v) Endotoxin-induced damages in mothers first of all depend on the individual susceptibility of these pregnant animals and (vi) the endotoxin tolerance induced by radio-detoxified endotoxin (TOLERIN) significantly protects both the mothers and the fetuses against endotoxin challenge.

Animals↗
PubMed1990

Specific removal of endotoxin from protein solutions by immobilized histidine.

A method for reducing endotoxin contamination in various solutions by immobilized histidine is described. Immobilized histidine is a porous adsorbent suitable for the adsorption of endotoxin with a high affinity over a wide range of pH and temperature and at low ionic strength (gamma/2 less than or equal to 0.1). When a purified endotoxin originating from Escherichia coli UKT-B was studied, the apparent dissociation constant between endotoxin and the adsorbent was 7.3 X 10(-13) M. The adsorbent was able to remove various kinds of endotoxin originating from gram-negative bacteria; the concentration of endotoxin was reduced from 1000 to less than 0.01 ng/ml in water. It is shown that the adsorbent specifically adsorbs endotoxin provided that the adsorption conditions are properly selected. Some examples of the specific removal of endotoxin from high-molecular-weight physiologically active substances such as tumor necrosis factor and lysozyme are shown.

Adsorption↗
PubMed1990

Optimization of detection of bacterial endotoxin in plasma with the Limulus test.

Detection and quantification of bacterial endotoxin in plasma by the Limulus amebocyte lysate test (or other assays for endotoxins) is hindered by the presence of inhibitors. Treatment of plasma to overcome inhibitory activities is required before plasma can be successfully assayed for endotoxin. We have conducted an investigation comparing the three most commonly used procedures (dilution-heating, trifluoroacetic acid oxidation, and chloroform extraction) for treatment of plasma before its assay for endotoxin with the chromogenic Limulus test. Initially, conditions were optimized for treatment of plasma by each of these methods. Subsequently, a direct comparison of the three plasma treatment procedures was performed with plasma spiked with known concentrations of endotoxin. The optimized dilution-heating procedure resulted in the most sensitive detection of endotoxin, with sensitivity approximately 10 times greater than the optimized trifluoroacetic acid oxidation procedure and approximately 100 times greater than treatment of plasma by chloroform extraction. Maximal detection of low concentrations of endotoxin by the chromogenic Limulus test was obtained by dilution of plasma fourfold with 0.15 mol/L NaCl followed by heating at 60 degrees C for 30 minutes. This procedure was simple, rapid, and did not involve addition of any reagents to plasma that could potentially add contaminating endotoxin.

Animals↗
PubMed1990

Dopamine beta-hydroxylase inhibition reveals a selective influence of endotoxin on catecholamine content of rat tissues.

Endotoxin is known to affect sympathetic nervous system (SNS) activity. However, it is unknown whether selective activation occurs in different tissues. The present work assessed SNS activity in several tissues of endotoxin-treated rats by measuring the accumulation of dopamine following dopamine beta-hydroxylase inhibition with disulfiram. Twenty-four hours following endotoxin injection (1 mg/kg), body weight and food intake were significantly reduced. The weight of spleen and liver was significantly greater in endotoxin-injected rats compared to either control animals or rats pair-fed the same quantity of food ingested by the endotoxin-treated rats. Norepinephrine (NE) content of heart, liver, and brown adipose tissue (BAT) was significantly lower in endotoxin-injected animals, but it was unchanged in spleen and gastrocnemius muscle. Endotoxin caused a significant elevation in the dopamine content of heart, liver, BAT, and gastrocnemius muscle, whereas it had no effect on spleen. The results suggest that SNS activity is increased in heart, liver, BAT, and gastrocnemius muscle 26 h after endotoxin injection.

Adipose Tissue, Brown↗
PubMed1987

Distinctive immunomodulatory effects of endotoxin and nontoxic lipopolysaccharide derivatives in lymphoid cell cultures.

Endotoxin derived from Serratia marcescens, as well as a hydrolyzed polysaccharide-rich derivative from the bacteria similar to the White-type polysaccharide (WPS), and hydrolyzed split products of endotoxin, including Lipid A and the nontoxic polysaccharide (PS), were studied in terms of their ability to induce mitogenic proliferation of murine spleen cells in vitro and enhancement of antibody formation to sheep erythrocytes. The intact endotoxin and the Lipid A component induced marked proliferative activity of normal lymphoid cells, but the PS components obtained after a 30 min or longer mild hydrolysis of the endotoxin had much less mitogenic activity. The WPS preparation retained mitogenic activity after 30 min but lost it during continued hydrolysis. Nevertheless, all of the components were marked adjuvants for murine spleen cells in vitro in terms of enhancing the antibody response to sheep red cells. Both the intact endotoxin as well as the Lipid A component induced interleukin-1 and interferons, including alpha/beta and gamma, following stimulation of spleen cell cultures for 24 h in vitro. Although only the endotoxin and Lipid A, but not the PS components, were mitogenic for murine splenocytes, all of these preparations had immune adjuvant effects and induced spleen cells to produce or release interferons. However, the PS-rich derivative did not induce tumor necrosis factor. These distinct properties of components of endotoxin indicate that the nontoxic PS-rich derivative, as compared to the toxic endotoxin or Lipid A, has some immunostimulatory activities but lacks others.

Adjuvants, Immunologic↗
PubMed1989

[An experimental study on the severe type of alcoholic liver disease--a pathogenetic role of potentiated activation of complement system by endotoxin after chronic ethanol consumption].

Endotoxemia frequently appears in severe type of alcoholic liver disease. However, we have little knowledge how endotoxin influences the progression of alcoholic liver injury. Thus, to study the causal mechanism for the progression to the severe type of alcoholic liver diseases, endotoxin (0.2 mg/100 g BW, E. Coli O26:B6) was intravenously injected in chronic ethanol-fed rats and controls, and then, rats were sacrificed after 16 hours of endotoxin treatment. The elevation of serum GOT and GPT activities induced by endotoxin was significantly higher in chronic ethanol-fed rats than controls, and these biochemical changes were well correlated with the grade of necrosis of liver histology. Furthermore, in chronic ethanol-fed rats, endotoxin treatment tremendously increased blood BUN and creatinine levels and produced the degeneration of renal tubuli with neutrophil infiltration into glomerulus. These experimental findings are very similar to the severe type of alcoholic liver disease. On the other hand, endotoxin significantly decreased serum values of CH50 in chronic ethanol-fed rats, but not in controls. Such alterations of CH50 induced by endotoxin were well correlated with the several parameters indicating the injury of liver and kidney. Therefore, the present study may indicate that chronic ethanol ingestion aggravates endotoxin-induced organ injury, and that the activation of complement system may associate with such progression of organ injury.

Animals↗
PubMed1989

Endotoxin-induced bacterial translocation: a study of mechanisms.

Previously, we documented that nonlethal doses of endotoxin cause the translocation (escape) of bacteria from the gut to systemic organs. The purpose of this study was to determine which portion(s) of the endotoxin molecule induces bacterial translocation and to examine the role of xanthine oxidase activity in the pathogenesis of endotoxin-induced bacterial translocation. Nonlethal doses of Salmonella endotoxin preparations (wild type, Ra, or Rb), containing the terminal portion of the core polysaccharide, induced bacterial translocation, whereas those preparations lacking the terminal-3 sugars (Rc, Rd, Re, or lipid A) did not induce bacterial translocation. Additionally, only those endotoxin preparations that induced bacterial translocation injured the gut mucosa, increased ileal xanthine dehydrogenase and oxidase activity, and disrupted the normal ecology of the gut flora, resulting in overgrowth with enteric bacilli. Inhibition of xanthine oxidase activity by allopurinol prevented endotoxin (Ra)-induced mucosal injury and reduced the incidence of bacterial translocation from 83% to 30% (p less than 0.01). These results suggest that endotoxin-induced bacterial translocation requires the presence of the terminal core lipopolysaccharide moiety and that xanthine oxidase-generated oxidants are important in the pathogenesis of endotoxin-induced mucosal injury and bacterial translocation.

Animals↗
PubMed1986

Mechanism of cardiac dysfunction in hearts from endotoxin-treated rats.

Myocardial performance was assessed in isolated perfused working hearts 3 hr after in vivo endotoxin administration (LD50-6 hr) to rats. Hearts removed from endotoxin-treated rats developed approximately 70% of the peak systolic pressure and 50% of the cardiac output (45% of the aortic flow and 50% of the coronary flow) at 25 cm H2O left atrial filling pressure (LAFP) compared to hearts from vehicle-injected controls. Hearts from endotoxin-treated rats were also characterized by decreased mechanical responsiveness to isoproterenol challenge at a high LAFP. These data suggest that myocardial dysfunction associated with endotoxin shock persists in vitro under conditions in which flow returning to the heart is not a limiting factor. Cyclic AMP accumulation was reduced in myocytes from endotoxin rats in response to 1 microM isoproterenol (29% of control values) and 1 microM forskolin (35% of control values) in both the absence and presence of phosphodiesterase inhibition with 0.2 mM isobutylmethylxanthine. Adenylate cyclase activity in crude membrane preparations of ventricular tissue from endotoxin-treated rats was unresponsive to challenge by isoproterenol and was reduced to 65% of control values by 100 micron GppNHp and by 10 mM NaF. Maximal specific binding of (-)[3H]dihydroalprenolol was decreased in membranes from endotoxin (56 +/- 2 fmol/mg) compared to control (64 +/- 2 fmol/mg) rats (P less than 0.05) but with similar antagonist affinities. These results suggest a decreased adrenergic responsiveness in myocytes and ventricular membrane preparations from endotoxin rats that may be linked to the reduction in myocardial adrenergic responsiveness during endotoxemia.

Adenylyl Cyclases↗
PubMed1988

Endotoxin-induced platelet activation in human whole blood in vitro.

The effect of purified bacterial endotoxin was studied on human platelets in vitro. In adding up to 1 microgram/mL of a highly purified endotoxin, we found neither aggregation nor ATP release in heparinized or citrated human platelet-rich plasma. On the other hand; endotoxin at concentrations as low as a few ng/mL (as may be found in septic patients) caused platelet aggregation in both heparinized and citrated human whole blood, as monitored by change in impedance, free platelet count, and size. Unlike collagen, the platelet aggregation with endotoxin occurred after a long lag phase, developed slowly, and was rarely coupled with measurable release of ATP. The platelet aggregating effect of endotoxin was dose-dependent and modified by exposure of the endotoxin to ionizing radiation. Thus, the activation of human platelets by "solubilized" endotoxin in plasma requires the presence of other blood cells. We propose that the platelet effect is mediated by monocytes and/or neutrophils stimulated by endotoxin.

Adenosine Triphosphate↗
PubMed1986

General effect of endotoxin on glucocorticoid receptors in mammalian tissues.

Considering the ubiquitous nature of glucocorticoid actions and the fact that endotoxin inhibits glucocorticoid action in the liver, we proposed to examine whether endotoxin affected extrahepatic actions of glucocorticoids. Fasted C57BL/6J mice were injected intraperitoneally with endotoxin (LD50) at 0800 and were killed 6 h later. Control mice were injected with an equal volume of saline. 3H-dexamethasone binding, measured by a new cytosol exchange assay utilizing molybdate plus dithiothreitol, in liver, kidney, skeletal muscle, spleen, lung, and heart tissue was significantly lower in treated than in control mice. The equilibrium dissociation constants were not significantly different, but the number of available binding sites in each tissue was reduced by endotoxin treatment. Phosphoenolpyruvate carboxykinase activity was significantly reduced in liver but not in kidney. Endotoxin treatment lowered glycogen content in liver but not in skeletal muscle. The reduction observed in the "a" form of liver glycogen synthase due to endotoxin was not seen in skeletal muscle glycogen synthase "a." These data support the proposal that endotoxin or a mediator of its action inhibits systemic glucocorticoid action. The results also emphasize the central role of the liver in the metabolic disturbances of the endotoxin-treated mouse.

Animals↗
PubMed1987

Endotoxin-induced production of thromboxane and prostacyclin by equine peritoneal macrophages.

Equine peritoneal macrophages were isolated and cultured in vitro to assess their ability to produce thromboxane (TxA2) and prostacyclin (PGI2) in response to endotoxin. Peritoneal macrophages (2.5 x 10(6)/ml) were incubated in tissue culture media, containing 1) no additive (nonstimulated control), 2) endotoxin (0.5 to 100 ng/ml) or 3) the calcium ionophore, A23187 (0.95 microM) for two and six h. Concentrations of the stable metabolites of TxA2 and PGI2 thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), in the incubation media were determined by radioimmunoassay. The concentrations of both metabolites increased from two to six h incubation. Endotoxin increased the production of TxA2 and PGI2 over the nonstimulated control values at both two and six h and endotoxin-induced concentrations of 6-keto-PGF1 alpha were higher at six than at two h. The response of macrophages to A23187 was similar to endotoxin. Mean eicosanoid concentrations did not differ among the range of endotoxin concentrations at either time; however there was significant curvilinear regression between endotoxin concentration and TxB2 at both times, and between endotoxin and 6-keto-PGF1 alpha at two h. The results indicate that equine macrophages may be a significant source of TxA2 and PGI2 during endotoxemia.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Endotoxin-induced hemodynamic and prostaglandin changes in ponies: effects of flunixin meglumine, dexamethasone, and prednisolone.

Shock was induced in four groups of anesthetized ponies with an intravenous injection of Escherichia coli endotoxin [125 micrograms/kg]. Five minutes after endotoxin injection, the ponies were given no treatment (group A), flunixin meglumine (FM:1.1 mg/kg) (group B), dexamethasone (2 mg/kg) (group C), or prednisolone (10 mg/kg) (group D). Additionally, FM was given every 3 hours, and the steroids were given at 3, 9, and 24 hours following endotoxin. Hemodynamic measurements were made during the 4-hour anesthetic period. Blood samples were collected for the analysis of prostaglandins, blood chemicals, and enzymes until death. Microspheres labeled with one of four radionuclides were used to determine regional blood flow at 0, 0.1, 1, and 2 hours after endotoxin was given. Plasma levels of both thromboxane and prostaglandin I2 increased from less than 1 ng/ml to between 3 and 5 ng/ml following the injection of endotoxin. The elevated thromboxane corresponded with high pulmonary arterial pressure [between 35 and 55 mm Hg] and low mean systemic arterial pressure (between 40 and 65 mm Hg) during the first 5-10 minutes following endotoxin. Increased concentrations of prostaglandin I2 were temporally related to systemic arterial hypotension, which occurred 1-2 hours following endotoxin in all groups except group B. The rise of prostaglandin I2 and hypotension were not observed in the flunixin meglumine-treated ponies. Dexamethasone was less effective, and prednisolone was ineffective in preventing the synthesis of prostaglandin I2 and the accompanying hemodynamic changes that occurred during the first 2 hours following endotoxin. This is probably due to the fact that steroids require a longer period of time before prostaglandin synthesis is reduced. Although not statistically significant, increased survival trends were observed in ponies treated with flunixin meglumine.

Animals↗
PubMed1987

Attenuation of endotoxin-induced increase in glucose metabolism by platelet-activating factor antagonist.

Platelet-activating factor (PAF) has recently been proposed as a putative mediator of various pathophysiologic events during endotoxemia. The aim of the present study was to determine the relative importance of PAF in producing the alterations in carbohydrate metabolism following endotoxin. Chronically catheterized conscious rats were treated with SRI 63-441, a specific PAF receptor antagonist, or saline prior to Escherichia coli endotoxin (100 micrograms/100 g body weight, LD10) administration. Hemodynamic and whole-body glucose kinetic changes, the latter assessed by a constant intravenous infusion of [6-3H] glucose, were determined throughout the 4-hr experimental protocol. Endotoxin induced a transient 30-35% reduction in mean arterial blood pressure (MABP) in animals treated with saline. The PAF-antagonist attenuated this hypotensive effect, and MABP was only reduced by 14-18%. Endotoxin increased plasma glucose and lactate levels, as well as the rate of glucose appearance (Ra) in saline-treated rats. The PAF antagonist reduced the hyperglycemia by 60-75% and tended to prevent the hyperlactacidemia. The endotoxin-induced elevation in glucose Ra was also attenuated by 55%. A similar degree of hyperglucagonemia was observed following endotoxin in both groups, and plasma insulin concentrations were not different. However, plasma catecholamine levels were significantly lower (30-70%) in endotoxemic rats treated with the PAF antagonist. These results suggest that the enhanced production of PAF following endotoxin may be responsible, at least in part, for the early hemodynamic changes. The role of PAF as a mediator of endotoxin-induced glucose dyshomeostasis, however, may be secondary to its hemodynamic effects.

Animals↗
PubMed1986

Ganglioside expression in macrophages from endotoxin responder and nonresponder mice.

Peritoneal macrophage ganglioside patterns and ganglioside sialic acid content were compared for two congenic strains of mice having differing responses to bacterial lipopolysaccharide. Resident macrophage ganglioside patterns from C3H/HeJ mice (endotoxin hyporesponsive) and C3H/HeN mice (endotoxin responsive) were similar. Macrophages elicited with phenol-extracted or butanol-extracted endotoxin showed distinctly more complex ganglioside patterns in C3H/HeN mice. C3H/HeJ macrophages showed distinct, but less complex changes when elicited with butanol-extracted endotoxin. As expected, there were minimal alterations induced by phenol-extracted endotoxin in the C3H/HeJ patterns. When injected with whole killed E. coli, both strains of mice exhibited complex ganglioside patterns; however, there were relative differences in the quantities of multiple gangliosides. Differences in ganglioside patterns were mirrored in the relative ratios of N-acetyl- to N-glycolylneuraminic acid. When macrophages were activated by administration of either endotoxin preparation, macrophage gangliosides from C3H/HeN mice always contained a higher proportion of N-acetylneuraminic acid compared with C3H/HeJ macrophage gangliosides. Oxidative metabolism of the macrophage populations was assessed by PMA-induced H2O2 release. This indicated that endotoxin activation produced an increase in PMA-induced H2O2 release as well as a shift of sialic acid class from the N-glycolyl type to the N-acetyl type. However, no direct correlation could be made between ganglioside composition, sialic acid content, and macrophage function. These data indicate that both ganglioside composition and sialic acid composition of macrophages are profoundly altered with endotoxin activation. The data further indicate that under conditions which C3H/HeJ mice respond to Gram-negative bacteria, their macrophage ganglioside patterns still differ from normal mice.

Animals↗
PubMed1986

Endotoxin-induced bovine mastitis: immunoglobulins, phagocytosis, and effect of flunixin meglumine.

Milk whey immunoglobulins (Ig) and phagocytosis of staphylococci by milk polymorphonuclear neutrophilic leukocytes (PMN) were measured in 12 cows (allotted to 6 pairs) during acute bovine mastitis induced by intramammary inoculation of endotoxin. Six of these cows (or 1 in each pair) were treated with flunixin meglumine and were compared with the others (given only saline solution). The endotoxin inoculation comprised 10 micrograms of Escherichia coli O26:B6 lipopolysaccharide injected into one of the rear quarters (mammae). Flunixin meglumine was administered parenterally at a dosage of 1.1 mg/kg every 8 hours (total of 7 doses) beginning at 2 hours after endotoxin was injected. Milk samples were obtained, and whey samples were prepared from each quarter of each cow 3 times before inoculation and at 2, 4, 8, 12, 24, 48, 72, 96, 120, 144, 168, and 336 hours after endotoxin was inoculated. Significant increases (P less than 0.05) in milk whey IgG1, IgG2, IgM, and IgA concentrations were observed in whey samples from endotoxin-inoculated quarters. Greatest relative increase was seen for IgG2. Increased whey Ig concentrations were not observed in quarters which were not inoculated with endotoxin. Concentrations of whey IgG1 and IgM in endotoxin-inoculated quarters were significantly (P less than 0.05) decreased in flunixin meglumine-treated cows, compared with those in saline solution-treated cows. Significant increases in phagocytosis of staphylococci by milk PMN were observed in whey samples from endotoxin-inoculated quarters. Significant differences in PMN phagocytosis were not found in whey samples from cows given flunixin meglumine when compared with whey samples from cows given saline solution.

Analysis of Variance↗
PubMed1985

Hepatic microvascular regulatory mechanisms. VI. Effects of lodoxamide tromethamine or phentolamine-HCl on early hemodynamic and glucoregulatory alterations evoked by endotoxin.

Initial changes in hepatic microvasculature and systemic arterial blood pressure were measured in non-fasted and anesthetized Sprague-Dawley rats receiving an i.v. infusion, or a topical application to the surface of the liver, of endotoxin (S. typhimurium) and/or phentolamine or lodoxamide. Circulating blood glucose and hepatic glycogen content were determined in infused rats. Injection of 10 mg per kg b.w. endotoxin, or topical administration of 10 micrograms endotoxin and/or antagonists, elicited no change in carotid (arterial) blood pressure. Infusion was accompanied by an elevation in blood glucose within 15 min and a decrease in hepatic glycogen content by 35 min. Injection of 1.0 mg per kg b.w. phentolamine blocked the endotoxin-induced hyperglycemia without affecting hepatic glycogenolysis. However, the alpha-adrenergic antagonist by itself provoked systemic hypotension, mild hypoglycemia, and hepatic glycogen depletion within 35 min. In vivo microscopy revealed that 10 micrograms endotoxin evoked immediate constriction of portal venules and periportal sinusoids. Vasoconstriction was accompanied by an increase in the percentage of microvascular segments containing decreased cellular blood flow velocity. These responses were blocked by 0.1 microgram lodoxamide but not by 100 micrograms phentolamine. The lodoxamide-induced inhibition was reversed by reapplication of 10 micrograms endotoxin 15 min following blockade. Given these results, it is suggested that (a) microvascular responses elicited by endotoxin were mediated by released constituents from intrahepatic mast cells and not by activation of alpha-adrenergic receptors, and (b) phentolamine blocked endotoxin-induced initial hyperglycemia by virtue of its hypoglycemic, glycogenolytic and/or hypotensive effects.

Amino Acids↗
PubMed1985

Effects of repeated endotoxin injections on prostanoids, hemodynamics, endothelial cells, and survival in ponies.

The objectives of this study were to determine the pathophysiological effects of increasing amounts of endotoxin administered intraperitoneally (IP) for 24 hr at which time an intravenous (IV) injection of endotoxin was given. The ability of flunixin meglumine (FM), a nonsteroidal antiinflammatory drug with antiprostaglandin activity, to provide protective effects was also determined. Eight ponies were divided into two groups of four ponies each; one group (untreated) received endotoxin only and the other group (treated) received endotoxin while being treated with flunixin. Hemodynamic and serum prostanoid changes were recorded for 26 hr during which time five IP and one IV endotoxin injections were given. Both groups behaved similarly until the intravenous endotoxin injection at 24 hr. At that time, the protective effects of flunixin became apparent by preventing increases in thromboxane and prostacyclin concentrations and by maintaining cardiac output, systemic arterial blood pressure, and blood flow to critical organs. Electron microscopic examination of pulmonary arteries of untreated animals revealed extensive endothelial cell damage while treatment with FM reduced this damage. A parallel study involving survival time in two groups of eight ponies each was also conducted using the same endotoxin and treatment protocol. At the end of 7 days, two of eight untreated ponies survived while six of eight treated ponies survived. It was concluded that FM prevented the release of prostanoids, maintained hemodynamics and blood flow nearer pre-endotoxin values, reduced vascular endothelial cell damage, and improved survival.

6-Ketoprostaglandin F1 alpha↗