Plasma catecholamines in the conscious rat during endotoxicosis

Blood pressure, heart rate, and plasma catecholamines were determined in conscious unanesthetized rats given intravenous saline or endotoxin (LPS from S. enteritidis). Rats were monitored for 6 hr and survival determined at 24 hr. Blood pressure and heart rate measurements were determined using implanted arterial cannulae. The first of two protocols involved surgical implantation of cannulae 24 hr prior to the administration of endotoxin (2.0 mg/kg) or saline. Significant hypotension during the first hour following endotoxin was observed but significant increases in heart rate were not observed until 3 hr. Plasma norepinephrine (NE) and epinephrine (E) were significantly elevated at 30 min. Norepinephrine remained elevated (6 times control) during 6 hr, whereas E was elevated (60 times control) at 30 min but was less elevated at 6 hr. The second protocol involved endotoxin or saline administration immediately following implantation of cannulae. In this group, 16.7 mg/kg of endotoxin or saline was given. All animals died and plasma catecholamines were elevated at higher levels than those of the first group. Results suggest marked elevations in plasma catecholamines during endotoxicosis. Additional data analysis suggests that plasma NE and E may provide an early index of impending circulatory shock.     

Protection of mice against lethal endotoxemia by lipid X is mediated through inhibition of neutrophil function

The effects of lipid X and 3-aza-lipid X on in vitro neutrophil function were related to their ability to inhibit the toxicity of endotoxin in galactosamine-sensitized mice. In vitro, lipid X and 3-aza-lipid X (100 ng/ml) blocked completely endotoxin (100 ng/ml)-enhanced neutrophil aggregation, superoxide anion generation, and release of beta-glucuronidase in response to a chemotactic tripeptide, f-met-leu-phe (10(-7) M). In vivo, lipid X at 250 micrograms/mouse (but not 3-aza-lipid X at a similar dose) protected groups of 10 mice from an otherwise lethal dose of endotoxin in galactosamine-sensitized mice when it was administered IV 4 hr or 2 hr before endotoxin challenge. The minimum effective dose of lipid X that could protect 50% of the challenged mice was calculated to be 715 micrograms/kg. However, lipid X failed to suppress neutrophil infiltration into the lungs. The ability of lipid X to inhibit endotoxin-induced neutrophil responses and to protect against lethal endotoxemia may be due to induction of early phase tolerance to endotoxin by the compound.     

In vivo and in vitro effects of endotoxin on vascular responsiveness to norepinephrine and signal transduction in the rat.

We investigated, after in vitro and in vivo exposure to gram-negative endotoxin, the altered responsiveness of rat aortic smooth muscle to catecholamines. Two hour exposure of aortic rings from normal rats to 100 ng/ml of Escherichia coli 0111:B4 endotoxin in vitro in an artificial medium supplemented with 5% fetal calf serum at 37 degrees C did not effect the basal and norepinephrine (NE)-stimulated (10 microM, 1 hr, 37 degrees C) phosphoinositide (PI) hydrolysis and isometric contractions induced by graded doses (1 nM to 10.0 microM) of NE. Increasing the incubation time with endotoxin to 18 hr did not alter the basal PI hydrolysis but significantly (P less than 0.05) decreased the NE-induced PI hydrolysis (30% inhibition) and contractile sensitivity to NE (increase of EC50 from 20.0 +/- 3.8 to 156.4 +/- 46.7 nM). Qualitatively similar results were obtained in experiments where rats were injected intravenously with buffer or an LD50 dose (10 mg/kg) of endotoxin. In these ex vivo measurements, only an 18 hr exposure to endotoxin caused significant (P less than 0.001) decreases in basal (58% inhibition) and NE-stimulated (75% inhibition) PI hydrolysis and in NE-induced isometric contractions (increase of EC50 from 11.0 +/- 3.3 to 664.1 +/- 280.0 nM). The results show that the endotoxin-induced hyporeactivity to alpha 1-adrenergic receptor stimulation 1) is markedly dependent on the length of endotoxin exposure, 2) does not require (although may be enhanced by) contact with blood cells and plasma, and 3) is paralleled by a decrease in both basal and NE-stimulated PI hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Contribution of platelet activating factor to hemodynamic and sympathetic responses to bacterial endotoxin in conscious rats

The effect of the platelet activating factor (PAF) antagonist WEB 2086 on blood pressure; heart rate; and plasma glucose, lactate, and catecholamine concentrations were examined following either PAF or endotoxin administration in conscious rats. PAF infusion (50 ng/kg/min for 60 min) resulted in a sustained hypotension, with tachycardia and elevated plasma norepinephrine (NE; 1.8-fold increase), epinephrine (E; 6.7-fold increase), and dopamine (DA; 1.0-fold increase) at 30 min after beginning infusion. Plasma NE, E, and DA became 4.1 (NE)-, 17.4 (E)-, and 3.3 (DA)-fold higher than control at 60 min after beginning infusion. Both the hemodynamic and plasma catecholamine alterations induced with PAF were completely blocked with WEB 2086 pretreatment. Bacterial endotoxin treatment (5 mg/kg, i.v. bolus) produced well-characterized responses of hypotension, tachycardia, hyperglycemia, hyperlactacidemia, and an elevation in plasma catecholamines. Whereas complete blockade of the hypotensive and tachycardic effect of endotoxin was achieved with WEB 2086 at 30 min following endotoxin, the increases in plasma catecholamines and lactate elicited by endotoxin were attenuated but remained significantly higher than control levels. Hyperglycemia following endotoxin was not altered by WEB 2086 treatment. In endotoxic rats pretreated with WEB 2086 there was significant hypotension, tachycardia, and hyperlactacidemia and an elevation in plasma catecholamines at both 60 and 120 min, but all were less severe compared to non-WEB 2086-treated endotoxic animals. The results demonstrate that WEB 2086 completely blocked early endotoxin-induced hypotension and tachycardia but not catecholamine elevation following endotoxin. This work suggests that sympathetic activation following endotoxin may be mediated by factors other than hypotension.     

Effects of catecholamines on plasma thyroid hormone levels in arctic charr, Salvelinus alpinus

Plasma levels of L-thyroxine (T4) and 3,5,3'-triiodo-L-thyronine (T3) were measured in arctic charr at 2, 6, or 24 hr after single intraperitoneal injection of epinephrine (E) or norepinephrine (NE). At a dose of approximately 1 microgram/g body wt (sufficient to cause a submaximal dermal melanophore pallor response) plasma T4 was usually elevated at 2 hr, consistently depressed at 6 hr, and unaffected at 24 hr. There was no effect of E on plasma [125I]T4 kinetics or [125I]T4 5'-monodeiodination to [125I]T3. Plasma T3 showed no consistent response to E or NE at any sampling time. At an E dose of 4 ng/g body wt (probably sufficient to cause a physiological elevation in plasma E level), neither plasma T4 nor T3 levels were altered at 6 hr. Acute depression in plasma T4 by the high doses of E and NE may reflect a local neurotransmitter role of catecholamines in inhibiting thyroidal T4 release through action at thyroidal, hypophysial, or hypothalamic levels.     

Effect of a selective V1 vasopressin receptor antagonist on the sequelae of endotoxemia in the conscious rat

The following studies were designed to evaluate the efficacy of a potent and selective AVP V1 receptor antagonist ([1-beta-mercapto-beta, beta-cy?lopentamethyleneproprionic acid, 2-(O-methyl)tyrosine-8-arginine vasopressin]; AVPRA) in limiting the sequelae of endotoxemia. At 0.5 and 1.0 hr after intravenous injection of 30 mg/kg S. enteritis endotoxin (LPS) to male Sprague-Dawley rats, AVP plasma concentrations were increased to 171 +/- 20 and 100 +/- 24 pg/ml, respectively, and were significantly greater than the vehicle control values of 1 pg/ml. Injection of LPS was accompanied by the following: a decreased survival rate (20%) with a mean survival time of 21.6 +/- 6 hr (n = 10), an increased heart rate (+ 84 +/- 22 bpm), a reduced circulating platelet count (23% of initial), and an acute hemoconcentration that was maximal at 30 min after injection of LPS. In a separate group of conscious rats, it was determined that AVPRA (1-100 mg/kg/hr) produced a dose-dependent, parallel and rightward shift in the AVP vasopressor dose-response curve: the highest dose of AVPRA (i.e., 100 micrograms/kg/hr) produced approximately a 1,000-fold shift in the AVP dose-response curve. Administration of AVPRA (1-100 micrograms/kg/hr) beginning 15 min prior to the injection of LPS and continuing for 6 hr did not significantly limit any of the sequelae produced by endotoxemia. These results suggest that, in this model, acute administration of a potent V1 AVP antagonist (AVPRA) is not sufficient to prevent the cardiovascular sequelae and mortality associated with endotoxemia.     

Effects of captopril on hemodynamic and metabolic parameters in awake endotoxemic Yucatan minipigs

Angiotensin II (AII), a potent vasoconstrictor, contributes to ischemic and decompensatory phases of shock. Captopril may benefit vital organ and tissue perfusion by inhibiting AII formation. We fitted 13 approximately 50-kg pigs with jugular, portal, hepatic vein, and carotid artery catheters, and hepatic artery and portal vein flow cuffs to quantitate portosystemic and transhepatic kinetics. We placed them in slings 72 hr later and following a 3-hr control period, they were infused with E. coli endotoxin at 15 micrograms/kg/hr for 6 hr. We kept eight as controls and five received a primed (2 mg/kg) continuous infusion (2 mg/kg/hr) of captopril 1 hr after initiation of endotoxin. Arterial hypotension developed by 60 min and hypoglycemia by 100 min in both groups; captopril had no effect on these parameters. Blood lactate increased from 7.8-32.1 mg/dl 80 min postendotoxin, and for the third to fifth hours of endotoxin infusion was significantly higher than those of the control group. 6-3H-glucose-derived appearance (Ra) values remained at 1.88-2.35 mg/kg/min throughout the experiment. Glucose disappearance (Rd) values were elevated from 60-120 min of endotoxin, increasing to 2.68-3.13 mg/kg/min versus 1.86 mg/kg/min preendotoxin. These changes corresponded to those in lactate, and incurred only a brief significant net glucose deficit (%Rd-%Ra) that peaked at 61.1% at 100 min. For 140-360 min postendotoxin, glucose balance was at most 8.3% in deficit (200 min) and 13.6% in positive balance (280 min) versus a net deficit of up to 25.4% (220 min) for the untreated group for much of the experiment. Portal and hepatic venous blood flow in captopril-treated pigs was lower than that in untreated pigs before endotoxin (8.2 and 10.0 ml/kg/min versus 12.9 and 17.9 ml/kg/min, respectively), but was not depressed following endotoxin infusion, versus 50% reductions in the untreated pigs, postendotoxin. Captopril maintained hepatosplanchnic blood flow and effected modest improvements in glucose kinetics.     

Beneficial effects of the peptidoleukotriene receptor antagonist, SK&F 104353, on the responses to experimental endotoxemia in the conscious rat

The purpose of this study was to examine the effects of the peptidoleukotriene receptor antagonist, SK&F 104353, on the responses to endotoxin in conscious male Sprague-Dawley rats. Administration of Salmonella enteritidis endotoxin (30 mg/kg i.v.; LD90) resulted in a decrease in the number of circulating platelets, leukopenia, an increase in hematocrit, and 0% survival at 24 hr. Pretreatment with SK&F 104353 (1 mg/kg, i.v. bolus followed by 3 mg/kg/hr, i.v. infusion for 6 hr) 5 min before injection of endotoxin produced steady state plasma drug levels of 1.6 micrograms/ml in naive animals and levels of approximately 3.4 micrograms/ml in endotoxemic animals (P less than 0.05). SK&F 104353 significantly attenuated the endotoxin-induced thrombocytopenia (P less than 0.05) but had no effect on either the endotoxin-induced early leukopenia or late leukocytosis. Additionally, SK&F 104353 significantly reduced the endotoxin-induced hemoconcentration (P less than 0.05) and improved survival to 30% at 48 hr (P less than 0.05). A higher dose of SK&F 104353 (2 mg/kg, i.v. bolus followed by 10 mg/kg/hr, i.v. infusion for 6 hr) did not produce any further benefit. These data indicate clearly the pathophysiologic role of peptidoleukotrienes in endotoxemia and suggest SK&F 104353 could be useful for ameliorating some of the deleterious sequelae associated with this condition.     

Metabolic effects of glucagon in endotoxemic minipigs

A treatment group of four 50-80-kg Yucatan minipigs was fitted with jugular, portal, hepatic vein, and carotid artery catheters, and hepatic artery and portal vein flow cuffs to quantitate transhepatic kinetics of glucose, lactate, and insulin. Three days later, they were placed in slings, and a primed-continuous intravenous infusion of 3-tritiated glucose was initiated to monitor whole body glucose kinetics. Following a 3-hour control period, an intravenous infusion of E. coli endotoxin was administered at 15 micrograms/kg/hr for 6 hours. After 1 hour of endotoxin infusion, glucagon was administered as a primed (50 micrograms/kg)-continuous (50 micrograms/kg/hr) intravenous infusion for 5 hours. These results were compared statistically to a control group of eight minipigs given endotoxin only. Glucagon caused a transient (less than 1 hour) peak elevation of arterial glucose levels due to increased hepatic glycogenolysis immediately following initiation of the glucagon infusion. Despite enhanced extrahepatic (renal) gluconeogenesis, plasma glucose concentrations decreased to the hypoglycemic levels of the control group, as glucagon was unable to overcome the relative endotoxic inhibition of hepatic gluconeogenesis. Pancreatic output of insulin increased sixfold resulting in threefold increments in transhepatic uptake and arterial serum insulin levels. Arterial lactate and pyruvate concentrations were elevated due to increased peripheral production and hepatic output. Survivability in the treatment group (75%) improved over the control group (33%).     

Plasma catecholamines during endotoxin infusion in conscious unrestrained rats: effects of adrenal demedullation and/or guanethidine treatment

We have examined the effect of E coli endotoxin infusion (41 micrograms kg-1 min-1 iv for 4 h) on plasma concentrations of epinephrine (E), norepinephrine (NE), and dopamine (DA) in the conscious unrestrained rat. Saline infusion did not change catecholamine concentrations from the preinfusion values of 230.8 +/- 32.9 pg ml-1 (E), 456.8 +/- 104.9 pg ml-1 (NE), and 49.0 +/- 19.9 pg ml-1 (DA). Endotoxin produced marked elevations in all three catecholamines. At 1 h, the plasma concentrations were 3,279 +/- 494.6 pg ml-1 (E), 1,670 +/- 137.0 pg ml-1 (NE), and 191.5 +/- 13.7 pg ml-1 (DA). Thereafter, concentrations of E decreased whereas concentrations of NE and DA increased. These increases were prevented by a combination of adrenal demedullation (28 days previously) and treatment with guanethidine (25 mg kg-1 iv, -24 h) ("sympathectomy"). Guanethidine alone markedly reduced the peak NE concentrations without affecting the E concentrations or the 1-h NE concentrations. Demedullation alone prevented the increase in E and reduced the 1-h NE concentrations. Survival in such "sympathectomized" animals was markedly reduced (survival at 4 h in rats receiving endotoxin alone, 100%: in "sympathectomized" animals receiving endotoxin, 12.5%). The tachycardia produced by endotoxin was attenuated in "sympathectomized" rats and mean arterial blood pressure fell rapidly. Endotoxin-induced hyperglycemia was prevented by "sympathectomy" and hypoglycemia was evident as early as 1 h after commencing the infusion. Endotoxin produced hypoinsulinemia in normal rats but did not change plasma insulin values in "sympathectomized" animals, although these animals showed a pre-endotoxin fasting hyperinsulinemia. An important protective role for catecholamines is suggested, especially in the early stages of shock.     

Role of the liver in endotoxin-induced hyperinsulinemia and hyperglucagonemia in rats

The intravenous administration of bacterial endotoxin to fasted rats elicited basal portal and systemic venous hyperinsulinemia and hyperglucagonemia. Enhanced pancreatic secretion of insulin and glucagon was implied by the elevated portal venous hormonal levels. Elevated insulin and glucagon levels were present at 4 hr after a 33 micrograms/100 gm intravenous endotoxin dose despite no fluctuation of the plasma glucose concentration. The role of the liver in the pancreatic hormonal response to endotoxin was investigated by infusing lipopolysaccharide slowly into the portal vein or systemic inferior vena cava. At doses of 33 and 100 micrograms per 100 gm, endotoxin administered via the systemic route stimulated significantly greater insulin and glucagon responses than did portal administration. Furthermore, rats with acute liver injury induced by partial (67%) hepatectomy, which depressed Kupffer cell phagocytosis, did respond to the 33 micrograms per 100 gm intraportal endotoxin dose with significantly greater hyperinsulinemia and hyperglucagonemia. These data suggest that hepatic Kupffer cells normally function to remove lipopolysaccharide from the portal venous blood and that at least at low pharmacological doses the pancreatic hormonal response to endotoxin is mediated by an unknown systemic mechanism.     

Anesthetic-induced changes in cardiovascular and small intestinal responses to endotoxin in the rat

The influence of anesthesia on endotoxin shock patterns in the rat was examined. Blood pressure, heart rate, arterial blood gases, glucose, lactate, and pathology of the small intestine were measured before and after endotoxin (40 mg/kg) challenge in male Sprague-Dawley rats. The three groups studied were: (1) enflurane anesthetized (N = 10), (2) ketamine anesthetized (N = 10), and (3) awake and unrestrained (N = 13). Measurements were made during 30 min prior to endotoxin injection (IV) and for 240 min afterward. Reflex tachycardia, which occurred in the awake group simultaneously with the initial endotoxin-induced hypotension, was not present during either enflurane or ketamine anesthesia. Significantly less gross intestinal pathology was found at 4 hr after endotoxin in the anesthetized groups compared to the awake group. These results suggest that the response of the sympathoadrenal system to the hypotension following endotoxin may be blunted in the anesthetized animal.     

Acceleration of recombinant tissue-type plasminogen activator-induced thrombolysis and prevention of reocclusion by the combination of heparin and the Arg-Gly-Asp-containing peptide bitistatin in a canine model of coronary thrombosis

The effect of tissue-type plasminogen activator (t-PA) alone or in combination with heparin, the Arg-Gly-Asp-containing peptide bitistatin, or both heparin and bitistatin was evaluated on thrombolysis time and acute reocclusion in a canine model of coronary thrombosis. Thrombus formation was elicited by electrolytic injury with a needle electrode to the endothelial surface of the circumflex coronary artery in the open-chest, anesthetized dog in the presence of a flow-limiting critical stenosis. Thirty minutes after spontaneous coronary artery occlusion, t-PA (1 mg/kg i.v. over 90 minutes) was administered. Group 1 was given t-PA alone; reperfusion occurred at 78.2 +/- 5.6 minutes with a reperfusion incidence of 60% (6/10). Group 2 received t-PA plus heparin (100 units/kg plus 50 units/kg/hr); reperfusion occurred at 61.9 +/- 9.1 minutes with a reperfusion incidence of 90% (9/10). Group 3 received t-PA plus heparin plus bitistatin (30 micrograms/kg plus 3 micrograms/kg/min); reperfusion occurred at 47.3 +/- 7.6 minutes (p less than 0.05 versus group 1) with a reperfusion incidence of 90% (9/10). Group 4 received t-PA plus bitistatin, and reperfusion occurred at 51.8 +/- 8.5 minutes; however, the reperfusion incidence was only 60% (6/10). In groups 1, 2, and 4, acute reocclusion occurred in more than 80% of the reperfused dogs, whereas in group 3 reocclusion occurred in 22% (2/9) of the reperfused dogs (p less than 0.05 versus group 1). The dose of heparin used in this study increased activated partial thromboplastin times 1.5-2.0-fold over control.(ABSTRACT TRUNCATED AT 250 WORDS)     

The vascular response to adrenergic stimulation in pithed rats following endotoxin

In vivo and in vitro studies have shown that the vascular response to catecholamine is attenuated during endotoxemia. The mechanism of such attenuation is complex and might involve high catecholamine-induced desensitization of adrenoceptors. The purpose of this study was to assess the vascular response to adrenergic stimulation after endotoxin (ETX) administration in pithed rats. In pithed rats, sympathetic outflow is controlled by stimulation, ETX does not elevate norepinephrine (NE), and there are no compensatory reflexes. Rats were pithed, curarized, and adrenal-demedullated. Preganglionic thoracolumbar nerves were stimulated (3 Hz, 10 V, 0.5 msec) for 1 hr after pithing, at which time the first set of frequency and NE-dose responses were assessed by measuring the peak increase in diastolic blood pressure. Intravenous ETX (1.5 mg/kg or 0.5 mg/kg) or saline was administered immediately after these measurements. A sham group was designed to mimic the falling blood pressure pattern seen in the endotoxin group during 1 hr after ETX was given by gradually decreasing the stimulation frequency. The second set of frequency and NE-dose responses were evaluated 1 hr after ETX, saline, or sham treatment. Plasma NE and epinephrine (EPI) were determined before and 1 hr after ETX (1.5 mg/kg) or saline injection. The results showed that blood pressure response to adrenergic stimulation was markedly attenuated in pithed rats following both high and low doses of ETX compared with the saline and sham groups. Plasma NE was not elevated by ETX insult in pithed rats. We propose that mechanisms other than high-catecholamine-induced adrenergic desensitization or hypotension account for the attenuated adrenergic responsiveness of the vasculature following ETX.     

Imbalance between plasma levels of thromboxane B2 and 6-keto-prostaglandin F1 alpha during subacute endotoxin-induced hyperdynamic sepsis or multiple organ failure syndrome in sheep.

We compared the time course of plasma and pulmonary lymph levels of thromboxane B2 (TxB2) and 6-keto-prostaglandin (PG)F1 alpha during the development of either the hyperdynamic phase of sepsis or of the multiple organ failure syndrome (MOFS) associated with sepsis in 26 chronically instrumented awake sheep with intravascular catheters and a chronic pulmonary lymph fistula. Using a continuous i.v. infusion of Escherichia coli endotoxin administered at a rate of 20 ng.kg-1.min-1 (group E20, n = 9) resulted in hyperdynamic septic shock with more than 75% of animals surviving after 72 h of continuous endotoxin administration. Infusing endotoxin at a higher dosage (40 ng.kg-1.min-1; group E40, n = 9) resulted in the development of respiratory failure and MOFS with death occurring within 55 hr of endotoxemia. Eight similarly instrumented sheep served as controls. Administration of endotoxin produced within 4 hr in both endotoxin groups a significant increase in arterial plasma concentration of TxB2, which was not significantly different between both endotoxin groups. Thereafter, plasma TxB2 concentrations progressively decreased in the E20 group to reach at 36 hr values significantly lower than those measured in control sheep not given endotoxin. In the E40 group, plasma TxB2 concentrations returned to baseline values during the development of a MOFS. The time course of TxB2 concentrations in pulmonary lymph in both endotoxin groups was similar to that measured in each group in plasma. 6-Keto-PGF1 alpha concentrations in arterial plasma and pulmonary lymph were significantly higher than in controls during the first 20 hr following the start of endotoxin infusion in both endotoxin groups and were not different between these groups. Thereafter, plasma and pulmonary lymph 6-keto-PGF1 alpha concentrations progressively returned to baseline values in the E20 group and remained at these levels up to the end of the study period (72 hr). In the E40 group, plasma 6-keto-PGF1 alpha concentrations also decreased to baseline values during the second day of endotoxemia but then significantly increased in sheep that survived more than 36 hr and developed a hypodynamic septic state. During the first 24 hr of endotoxemia, the plasma TxB2/6-keto-PGF1 alpha ratio was similar in controls and in both endotoxin groups. During the second study day, TxB2/6-keto-PGF1 alpha ratio progressively decreased in both endotoxin groups to reach and maintain values significantly lower than those measured in controls at 36 hr in the E40 group and at 52 hr in E20 group.(ABSTRACT TRUNCATED AT 400 WORDS)     

Misoprostol but not antacid prevents endotoxin-induced gastric mucosal injury

Many of the complications of septic shock are believed to be a consequence of elevated circulating levels of tumor necrosis factor (TNF), which is an important mediator of tissue injury. Prostaglandins (PGs) of the E series have recently been reported to inhibit TNF production in vitro. We investigated the in vivo effect of misoprostol, a PGE1 analog, on endotoxin-induced gastric mucosal injury and TNF production. For the gastric mucosal injury studies, groups of animals were pretreated with intragastric misoprostol (100 and 200 micrograms/kg) or with antacid (2 ml/animal of Maalox Plus) 30 min prior to a challenge with intravenous E. coli lipopolysaccharide (LPS) at 5.0 mg/kg. Stomachs were examined 3 hr after LPS. Systemic endotoxin alone induced microscopic edema, vascular congestion, and polymorphonuclear (PMN) infiltration of the gastric mucosa. Pretreatment with misoprostol, but not with antacid, significantly and dose-dependently reduced the gastric mucosal injury. For the TNF studies, groups of rats were given either misoprostol (100 or 200 micrograms/kg, intragastric), or saline 1 hr prior to LPS challenge. Serum samples were obtained 1.5 hr after LPS challenge. Misoprostol dose-dependently and significantly (P less than 0.01) inhibited TNF activity. We conclude that misoprostol is a potent inhibitor of TNF systemic production and inhibits the gastric mucosal injury induced by endotoxemia. These studies suggest a potentially important therapeutic role for misoprostol in inflammatory diseases in which TNF exerts a contributory role.     

Effect of meningococcal endotoxin in a rabbit model of shock.

Endotoxin in the form of a lipooligosaccharide (LOS) plays a key role in the development of shock in meningococcal sepsis. To examine hemodynamic and biochemical alterations during meningococcal endotoxic shock, we established a rabbit model. Thirty-nine rabbits, weighing 2.5-4.4 kg, were studied. After anesthesia with intramuscular ketamine (20 mg/kg) and xylazine (4 mg/kg), femoral venous and arterial catheters were inserted. Control animals received only saline, while rabbits in each of four additional groups were given LOS in 10-fold increments from 0.1 microgram/kg to 100 microgram/kg. Mean arterial pressure (MAP), heart rate (HR), respirations (RR), temperature (T), urine output, and arterial blood gases (pH, PCO2, PO2, and bicarbonate) were determined at baseline and hourly. Endotoxin levels and TNF levels were measured at 30, 60, 120, 180, 240, 300, and 360 min post-LOS. Survival was recorded. One-way analysis of variance (ANOVA) and the Scheffe procedure, paired samples t-test, two-tailed t-test, and Fisher's exact test were used. Pearson's coefficients were calculated. Animals receiving meningococcal LOS developed tachycardia and compensated metabolic acidosis with an initially normal pH and MAP. With progression of the shock state, the pH decreased and hypotension ensued. Maximal levels of endotoxin were measured 30 min after LOS injection and declined during the ensuing 6 hr. TNF rose from undetectable to markedly elevated levels and peaked at 60-120 min post-LOS. Increasing the amount of injected endotoxin produced more profound degrees of shock until a dose of 10.0 micrograms/kg was reached. There was no correlation between serum TNF at 60 min and survival at 6 hr or 24 hr.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of repetitive low-dose endotoxin on liver parenchymal and Kupffer cell fibronectin release

Repetitive low-dose endotoxin, at a dose which will result in endotoxin tolerance, produces a marked but transient 2- to 3-day increase in plasma fibronectin. This elevation of fibronectin appears to contribute to increased hepatic Kupffer cell phagocytic function observed with repetitive low-dose endotoxin administration. Although numerous cell types synthesize fibronectin, hepatocytes are believed to be the major cell source of fibronectin in the plasma. Since Kupffer cells also synthesize fibronectin, we sought to determine the relative contribution of hepatic Kupffer cells, as compared to parenchymal cells, to the elevation of plasma fibronectin following repetitive low-dose endotoxin administration. Kupffer cells isolated from rats previously treated for 3 consecutive days with 100 micrograms Salmonella enteritidis endotoxin released greater (p less than 0.01) amounts of fibronectin over time in culture (3, 6, 12 and 24 hr) as compared to Kupffer cells isolated from normal rats. Experiments in which fibronectin was normalized to DNA content of the cells in culture also showed similar results for fibronectin release by Kupffer cells (normal: 2.9 +/- 0.5 ng per microgram DNA per 24 hr; endotoxin-treated: 53.3 +/- 1.3 ng per microgram DNA per 24 hr). Hepatocytes from endotoxin-treated rats released less (p less than 0.01) fibronectin over time than hepatocytes isolated from normal animals. As with Kupffer cells, results for fibronectin release by hepatocytes were similar when normalized to the DNA content (normal: 190.0 +/- 9.4 ng per microgram DNA per 24 hr; endotoxin-treated: 83.3 +/- 4.2 ng per microgram DNA per 24 hr).(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of angiotensin I and glucagon in canine endotoxin shock: effect of converting enzyme inhibitor and prior immunization

he intermediate and latter stages of canine endotoxin shock are characterized by a progressive decrease in cardiac output, increase in total peripheral resistance, and hypoglycemia. We have hypothesized that the renin-angiotensin system and glucagon may mediate the loss of cardiovascular and glucose homeostasis. E. Coli endotoxin shock (1 mg/kg; 055:B5) was induced in three groups of dogs and systemic hemodynamics, angiotensin I activity, and glucagon were monitored for 5 hr; endotoxin shock (n = 13); endotoxin shock + prior immunization with J5 mutant of E coli 0111 (n = 5); Endotoxin + captopril (20 micrograms/kg/hr; n = 9); and sham-operated time-matched controls (n = 8). Thirty minutes postshock, angiotensin I and glucagon began to increase. Angiotensin I activity reached a peak at 60 min postendotoxin (90 +/- 25 vs 5 +/- ng/ml/hr; p less than 0.001) and plateaued. Increased glucagon levels plateaued at 3.5 hr postshock (1500 +/- 200 vs 155 +/- 77 pg/ml; p less than 0.001). Cardiac output began to progressively decrease, total peripheral resistance began to increase, and persistent hypoglycemia developed at 3 hr postshock. Captopril inhibited the increase in total peripheral resistance and had no effect on the decrease in cardiac output or the hypoglycemia. The initial glucagon response was attenuated but there was no difference at 5 hr (950 +/- 150 vs 1200 +/- 200 pg/ml). Prior immunization significantly preserved cardiac output, total peripheral resistance, plasma glucose levels, glucagon levels, and angiotensin I activity. It is concluded that 1) the renin-angiotensin system is a physiologic and not a pathophysiologic compensatory mechanism during the course of endotoxin shock and that inhibition of this system is deleterious; 2) glucagon may serve as an important mediator of both the myocardial dysfunction and glucose dyshomeostasis of endotoxin shock; and 3) immunological inhibition of the initial phase of endotoxin shock significantly preserves cardiovascular and glucose homeostasis and adds support to the concept that the initial vascular phase of endotoxin shock plays a primary role in determining the severity of the endotoxin/septic shock syndrome.     

Determination of an estradiol dose-response relationship in the modulation of ethanol intake

BACKGROUND: Estradiol (E2) potentiates the self-administration of numerous psychoactive drugs in female rodents. An analogous modulatory role of E2 on ethanol consumption remains unresolved because of examination of limited doses. The purpose of this study was to delineate a dose-response relationship for E2 on ethanol intake with an extended range and number of E2 doses. METHODS: Female Long-Evans rats had continuous access (22 hr/day) to both 10% ethanol (10E) solution and water. After the establishment of stable 10E intake baselines, rats were assigned to one of seven dose groups balanced for 10E intake [sham-operated (Shm) or ovariectomized (Ovx) plus E2 (microgram/kg)]: Shm + 0, Ovx + 0, Ovx + 0.05, Ovx + 0.15, Ovx + 0.5, Ovx + 1.5, and Ovx + 5. Ethanol preference drinking was evaluated during 25 consecutive days of E2 replacement treatment, and trunk blood was collected for the determination of plasma E2 and progesterone concentrations. RESULTS: Chronic E2 replacement regimens (0.05-1.5 micrograms/kg) dose-dependently augmented 10E intakes and ethanol preference ratios without concomitantly altering water consumption. Despite the maintenance of 2- to 3-fold greater plasma E2 levels, a supraphysiologic E2 dose (5 micrograms/kg) failed to precipitate ethanol intakes in excess of levels observed after treatment with a high physiologic E2 dose (1.5 micrograms/kg). Plasma progesterone concentrations were significantly increased in treatment groups (1.5 and 5 micrograms/kg E2) that exhibited corresponding significant increases in ethanol consumption. CONCLUSIONS: A positive dose-response relationship between E2 and ethanol intake (incremental increases in E2 dose corresponded to incremental increases in intake) was apparently limited to a physiologic concentration range, because a supraphysiologic dose failed to elicit an additional stepwise increase in ethanol intake. These findings stipulate a modulatory role for E2 in the regulation of moderate ethanol intake and suggest that endogenous fluctuations of E2 may alter the propensity toward consumption in women and in female animal models of ethanol self-administration.