nitroarginine and Escherichia-coli-Infections

During chronic total parenteral nutrition (TPN), liver glucose uptake and lactate release are markedly elevated. However, in the presence of an infection, hepatic glucose uptake and lactate release are reduced. Glucose delivery (the product of liver blood flow and inflowing glucose concentration) is a major determinant of liver glucose uptake. Hepatic blood flow is increased during infection, and increased nitric oxide (NO) biosynthesis is thought to contribute to the increase. Our aim was to determine if the increase in liver blood flow served to limit the infection-induced decrease in hepatic glucose uptake and metabolism. Chronically catheterized conscious dogs received TPN for 5 days at a rate designed to match daily basal energy requirements. On the third day of TPN administration, a sterile (SHAM) or Escherichia coli (E. coli)-containing (INF) fibrin clot was implanted in the peritoneal cavity. Forty-two hours later, somatostatin was infused with intraportal replacement of insulin (10 +/- 2 v 23 +/- 2 microU/mL, SHAM v INF, respectively) and glucagon (22 +/- 4 v 90 +/- 8 pg/mL) to match concentrations observed in sham and infected animals. Tracer and arteriovenous difference techniques were used to assess hepatic glucose metabolism. Following a 120-minute basal sampling period, sham and infected animals received either intraportal saline or N(omega)-nitro-L-arginine (L-NNA; 37 microg x kg(-1) x min(-1)) infusion for 180 minutes. Isoglycemia (120 mg/dL) was maintained with a variable glucose infusion. In the infected group L-NNA infusion decreased hepatic arterial blood flow (23.3 +/- 0.7 to 8.6 +/- 0.5 mL x kg(-1) x min(-1)), but not portal vein blood flow. Neither portal vein nor hepatic artery blood flow were altered by L-NNA infusion in the sham group. Hepatic glucose uptake and lactate metabolism were not altered by L-NNA infusion in either group. In summary, during infection, an increase in NO biosynthesis contributes to the increase in hepatic arterial blood flow, while it exerts no effect on hepatic glucose metabolism.

Topics: Adaptation, Physiological; Animals; Dogs; Enzyme Inhibitors; Escherichia coli Infections; Female; Glucose; Hemodynamics; Hindlimb; Hormones; Liver; Liver Circulation; Nitroarginine; Parenteral Nutrition, Total; Reference Values

To evaluate the effect of treatment with a combination of nitric oxide synthase inhibitors and inhaled nitric oxide on systemic hypotension during sepsis.. Prospective, randomized, controlled study on anesthetized animals.. A cardiopulmonary research laboratory.. Forty-seven male adult Sprague-Dawley rats.. Animals were anesthetized, mechanically ventilated with room air, and randomized into six groups: a) the control group (C, n=6) received normal saline infusion; b) the endotoxin-treated group received 100 mg/kg i.v. of Escherichia coli lipopolysaccharide (LPS, n=9); c) the third group received LPS, and 1 hr later the animals were treated with 100 mg/kg i.v. Nw-nitro-L-arginine (LNA, n=9); d) the fourth group received LPS, and after 1 hr, the animals were treated with 100 mg/kg i.v. aminoguanidine (AG, n=9); e) the fifth group received LPS and 1 hr later was treated with LNA plus 1 ppm inhaled nitric oxide (LNA+NO, n=7); f) the sixth group received LPS and 1 hr later was treated with aminoguanidine plus inhaled NO (AG+NO, n=7). Inhaled NO was administered continuously until the end of the experiment.. Systemic mean blood pressure (MAP) was monitored through a catheter in the carotid artery. Mean exhaled NO (ENO) was measured before LPS (T0) and every 30 mins thereafter for 5 hrs. Arterial blood gases and pH were measured every 30 mins for the first 2 hrs and then every hour. No attempt was made to regulate the animal body temperature. All the rats became equally hypothermic (28.9+/-1.2 degrees C [SEM]) at the end of the experiment. In the control group, blood pressure and pH remained stable for the duration of the experiment, however, ENO increased gradually from 1.3+/-0.7 to 17.6+/-3.1 ppb after 5 hrs (p< .05). In the LPS treated rats, MAP decreased in the first 30 mins and then remained stable for 5 hrs. The decrease in MAP was associated with a gradual increase in ENO, which was significant after 180 mins (58.9+/-16.6 ppb) and reached 95.3+/-27.5 ppb after 5 hrs (p< .05). LNA and AG prevented the increase in ENO after LPS to the level in the control group. AG caused a partial reversal of systemic hypotension, which lasted for the duration of the experiment. LNA reversed systemic hypotension almost completely but only transiently for 1 hr, and caused severe metabolic acidosis in all animals. The co-administration of NO with AG had no added benefits on MAP and pH. In contrast, NO inhalation increased the duration of the reversal in MAP after LNA, alleviated the degree of acidosis, and decreased the mortality rate (from 55% to 29%).. In this animal model, LPS-induced hypotension was alleviated slightly and durably after AG, but only transiently after LNA. Furthermore, co-administration of NO with AG had no added benefits but alleviated the severity of metabolic acidosis and mortality after LNA. We conclude that nitric oxide synthase (NOS) inhibitors, given as a single large bolus in the early phase of sepsis, can exhibit some beneficial effects. Administration of inhaled NO with NOS inhibitors provided more benefits in some conditions and therefore may be a useful therapeutic combination in sepsis. NO production in sepsis does not seem to be a primary cause of systemic hypotension. Other factors are likely to have a major role.

Topics: Administration, Inhalation; Animals; Disease Models, Animal; Drug Evaluation, Preclinical; Drug Therapy, Combination; Escherichia coli Infections; Free Radical Scavengers; Guanidines; Hemodynamics; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Random Allocation; Rats; Rats, Sprague-Dawley; Shock, Septic; Time Factors

The contractile and electrical properties of the mouse diaphragm during endotoxemia were studied, and the possible role of nitric oxide (NO) on these changes was investigated. The mice were injected intraperitoneally with E. coli. lipopolysaccharide (endotoxin, LPS) at various times before isolation of the diaphragm to induce endotoxemia. It was observed that direct twitch tension was slightly increased, and that there was a significant increase in tetanic tension when compared with controls. The potentiation of direct twitch tension induced by a Cl--channel blocker (9-anthracene carboxylic acid), but not the potentiation by a Na+-channel activator (veratridine) or by K+-channel blockers (uranyl ion, 4-aminopyridine and tetraethylammonium ion), was attenuated in the diaphragm of LPS-treated mice. Moreover, the resting membrane potential was significantly reduced and the membrane input resistance was significantly increased, largely due to a decrease in Cl--conductance. However, the membrane K+-conductance remained unaltered. These results imply that the sarcolemmal Cl--channel is markedly affected in the mouse diaphragm during endotoxemia. These changes of contractile and electrical characteristics of the mouse diaphragm during endotoxemia could be reversed by treatment with dexamethasone and N(G)-nitro-L-arginine (NO synthase inhibitors). On the other hand, in in vitro studies, LPS (20 microg/ml), by itself, applied directly to the diaphragm, did not alter the muscle contractions or the membrane potentials. A NO donor, added to the diaphragm bath, increased the tetanus/twitch ratio and induced a transient depolarization. All of these findings suggest that LPS may, at least in part, affect the sarcolemmal electrical properties and muscle contractions during endotoxemia through the L-arginine:NO pathway.

Topics: Animals; Anthracenes; Chloride Channels; Dexamethasone; Diaphragm; Endotoxemia; Escherichia coli Infections; Female; Lipopolysaccharides; Male; Membrane Potentials; Mice; Mice, Inbred ICR; Muscle Contraction; Muscle, Smooth; Nitric Oxide; Nitroarginine; Nitroprusside

In this study we compared the circulatory effects of the arginine analogue non-specific nitric oxide synthase (NOS) inhibitor N omega-nitro-L-arginine (NNA), and the specific inducible NOS (iNOS) inhibitor S-methylisothiourea (SMT) and S-(2-aminoethyl)-isothiourea (AEST) in a hyperdynamic endotoxemic dog model. Mean arterial pressure (MAP), cardiac output (CO), and myocardial contractility (MC) were measured. A hyperdynamic circulatory response was elicited with a 2-h infusion of a total dose of 5.3 micrograms/kg E. coli endotoxin (ETX). NOS inhibitory treatment (2 mg/kg) was administrated from the 45th min of endotoxemia. ETX induced a hyperdynamic circulatory response, and a significant myocardial depression. NNA induced a prolonged, SMT a transient increase in MC, both drugs elevated MAP, but decreased CO. AEST significantly prolonged the elevation in CO, but did not affect MAP. Selective inhibition of the iNOS may be a beneficial in sepsis.

Topics: Animals; beta-Aminoethyl Isothiourea; Blood Circulation; Blood Pressure; Cardiac Output; Disease Models, Animal; Dogs; Endotoxemia; Endotoxins; Enzyme Inhibitors; Escherichia coli; Escherichia coli Infections; Hemodynamics; Isothiuronium; Myocardial Contraction; Nitric Oxide Synthase; Nitroarginine; Ventricular Function, Left; Ventricular Pressure

To evaluate the possible effects of a combination of systemic nitric oxide synthesis inhibition (to increase mean arterial blood pressure) and nitric oxide inhalation (to decrease pulmonary vascular pressure) in porcine endotoxin shock.. Prospective trial.. Laboratory at a large university medical center.. Ten pathogen-free pigs weighing 19 to 25 kg.. After surgical preparation, all pigs received a continuous infusion of Escherichia coli lipopolysaccharide endotoxin (15 micrograms/kg/hr) for 2 hrs. After 1 hr of endotoxemia, nitric oxide inhalation (50 parts per million) and NG-nitro-L-arginine infusion (50 mg/kg/hr) were initiated in six pigs. Four pigs served as controls and received only a lipopolysaccharide infusion.. NG-nitro-L-arginine infusion and nitric oxide inhalation prevented the further decrease in mean arterial blood pressure seen in the control pigs (p < .05), but did not restore mean arterial blood pressure back to basal values. Cardiac output decreased significantly compared with controls during NG-nitro-L-arginine infusion/nitric oxide inhalation (p < .01). Systemic vascular resistance, which was below basal values in the controls after 2 hrs of endotoxemia, was markedly increased by NG-nitro-L-arginine/nitric oxide, to higher values than those observed in the basal state (p < .01). In the control pigs, mean pulmonary arterial pressure and pulmonary vascular resistance showed a biphasic increase. In the NG-nitro-L-arginine/nitric oxide treated group, the second phase increase in mean pulmonary arterial pressure did not occur (p < .01). However, there was no difference in pulmonary vascular resistance between the groups. Renal vascular resistance was unchanged in controls, while NG-nitro-L-arginine/nitric oxide induced a four-fold increase in renal vascular resistance (p < .001). There was no statistical difference in urine production between the groups. PaO2 values were higher and PaCO2 tensions were lower in the treated pigs than in the controls. Arterial pH and base excess did not differ. Arterial plasma epinephrine, norepinephrine, and neuropeptide Y concentrations increased during the lipopolysaccharide infusion in both groups, with a tendency toward higher concentrations in the pigs receiving NG-nitro-L-arginine/nitric oxide. Arterial plasma endothelin-1-like immunoreactivity in these pigs was significantly higher at the end of the treatment than in the controls.. In this model of porcine endotoxin shock, the combination of NG-nitro-L-arginine infusion and nitric oxide inhalation attenuated pulmonary hypertension and improved gas exchange; it also prevented development of further systemic hypotension, but impaired cardiac output and increased systemic and renal vascular resistances to supranormal levels. NG-nitro-L-arginine/nitric oxide did not reduce sympathetic nervous system activation or metabolic acidosis.

Topics: Administration, Inhalation; Animals; Arginine; Drug Evaluation, Preclinical; Drug Therapy, Combination; Endothelins; Escherichia coli Infections; Female; Infusions, Intravenous; Male; Neuropeptide Y; Nitric Oxide; Nitroarginine; Shock, Septic; Specific Pathogen-Free Organisms; Swine

The effects of NW-nitro-L-arginine (L-NAG) and dexamethasone in the microcirculatory changes observed in early stages of endotoxemia was investigated in male hamsters treated with Escherichia coli lipopolysaccharide (LPS). The cheek pouch was studied in vivo by means of intravital microscopy and mean arterial and venous pressures, mean arteriolar internal diameter, spontaneous arteriolar vasomotion, microvascular blood flow, macromolecular permeability, leukocyte adhesion, and mean survival time were evaluated in animals treated with either LPS alone or the combination of LPS with L-NAG, an inhibitor of both the constitutive and inducible NO synthases (NOs). The intravenous injection of LPS (100 mg/kg) elicited a significant reduction in mean arterial blood pressure (MABP) and arteriolar blood flow. The observed arterioles dilated and the spontaneous vasomotion ceased. The combination LPS + L-NAG, both given intravenously, prevented the reduction of MABP and the vasodilation but did not help either the reduction of arteriolar blood flow or the cessation of vasomotion. In order to separate the effect of the two NOs, a group of hamsters was pretreated with dexamethasone (10 mg/kg, also intravenously) which inhibits the induction of the inducible NO synthase (iNOs). In this group, the hypotension, vasodilation, and cessation of vasomotion were prevented but the decrease in arteriolar blood flow was not affected. The mean survival time was significantly decreased by the combination of LPS + L-NAG (35 +/- 6 h) and significantly increased by the pretreatment with dexamethasone (92 +/- 5 h) compared to LPS alone (56 +/- 7 h).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Capillary Permeability; Cell Adhesion; Cheek; Cricetinae; Dexamethasone; Escherichia coli Infections; Hemodynamics; Injections, Intravenous; Lipopolysaccharides; Male; Microcirculation; Microscopy, Video; Nitroarginine; Shock, Septic

Septic shock is characterized by systemic vasodilation and an impaired reactivity to vasoconstrictor agents. It has been suggested that an excessive release of nitric oxide has a role in this hemodynamic derangement.. To investigate whether inhibition of nitric oxide synthesis by the administration of N omega-nitro-L-arginine (LNNA), improves the vasoconstrictor effects of catecholamines in sepsis.. Mechanically ventilated and pentobarbital-anesthetized sheep received either no treatment (n = 6) or LNNA (100 mg/kg IV bolus, n = 4). Other sheep (septic group) received live Escherichia coli (E coli) (1,5* 10(9) micro-organisms/kg over 30 min) followed 1 hour later by either no treatment (n = 5) or LNNA (100 mg/kg IV bolus, n = 7). After those interventions, all sheep were given noradrenaline in a continuous IV infusion at three different doses (0.5, 1.5, and 4.5 micrograms, kg-1, min-1). Cardiovascular parameters were recorded at maximal blood pressure response achieved with each dose.. The administration of live E coli to the septic group resulted in systemic hypotension, high cardiac output, and hyperlactatemia. The LNNA caused a significant systemic and pulmonary vasoconstriction in both septic and nonseptic sheep. In nonseptic sheep, noradrenaline induced a significant increase in systemic vascular resistance (from 2,973 +/- 637 to 4,561 +/- 1,287 dyn/s/cm-5/m-2), whereas the increase caused in those that received LNNA was nonsignificant (5,562 +/- 3,489 to 6,693 +/- 2,871 dyn, s, cm-5, m-2). Septic sheep showed a nonsignificant vasoconstriction during the infusion of noradrenaline (from 1,438 +/- 1,132 to 2,244 +/- 1,391 dyn/s/cm-5/m-2). However, treatment with LNNA markedly improved the vasoconstrictor effect of noradrenaline (from 2,804 +/- 2,317 to 4,894 +/- 3,435 dyn/s/cm-5/m-2). The dose-response curve of systemic vascular resistance in these LNNA-pretreated septic sheep became very similar to the corresponding curve obtained in nonseptic animals.. Inhibition of nitric oxide synthesis by the administration of LNNA significantly improves the vasoconstrictor effect of noradrenaline in septic sheep, allowing an increase in systemic vasomotor tone similar to that observed in nonseptic sheep. It is concluded that increased synthesis of nitric oxide contributes to the depressed vascular reactivity to vasoconstrictor agents characteristic of sepsis.

Topics: Animals; Arginine; Dose-Response Relationship, Drug; Escherichia coli Infections; Nitric Oxide; Nitroarginine; Norepinephrine; Sheep; Shock, Septic; Vascular Resistance; Vasoconstriction

To study the role of nitric oxide in the hemodynamic changes of sepsis.. Prospective, randomized, controlled, intervention study.. Twenty-five sheep randomized to four groups: Group A (n = 8, nonseptic sheep) received NG-nitro L-arginine (20 mg/kg i.v.) followed 15 mins later by L-arginine (200 mg/kg i.v.); group B (n = 4, nonseptic sheep) received L-arginine followed 15 mins later by NG-nitro L-arginine; group C (n = 7, septic sheep) received NG-nitro L-arginine (20 mg/kg i.v.) alone; group D (n = 6, septic sheep) received L-arginine (200 mg/kg i.v.) followed by NG-nitro L-arginine (20 mg/kg i.v.).. Sheep were anesthetized with pentobarbital, mechanically ventilated and monitored with a pulmonary artery catheter, a peripheral artery catheter, and a Miller catheter in the left ventricle. Sepsis was induced by the intravenous administration of live Escherichia coli (1.5 x 10(9) microorganisms/kg over 30 mins), which resulted in systemic hypotension, pulmonary hypertension, high cardiac output, and hyperlactatemia. Acetylcholine was administered before and after each intervention.. In nonseptic sheep (groups A and B) NG-nitro L-arginine induced an increase in mean blood pressure (BP), pulmonary arterial pressure, and systemic and pulmonary vascular resistances, accompanied by a decrease in cardiac index and the first derivative of left ventricular pressure. L-arginine administered to normal sheep induced systemic vasodilation. In the sepsis groups (groups C and D), the increases in BP and systemic vascular resistances induced by NG-nitro L-arginine were significant but less marked than in nonseptic sheep. Pretreatment of septic sheep with L-arginine totally abolished the NG-nitro L-arginine induced increases in systemic and pulmonary vascular resistances in this group. The administration of L-arginine in these animals induced both systemic and pulmonary vasodilation. Acetylcholine-mediated vasodilation was severely impaired in sepsis. In this condition, pretreatment with L-arginine improved the response to acetylcholine.. These data support the view that nitric oxide plays a significant role in modulating systemic and pulmonary vasomotor tone in normal and septic sheep. L-arginine produced systemic vasodilation in normal sheep, whereas both systemic and pulmonary vasodilation were observed in septic animals. The impaired response to an endothelium-dependent vasodilator in sepsis was improved by the previous administration of L-arginine.

Topics: Acetylcholine; Animals; Arginine; Disease Models, Animal; Drug Evaluation, Preclinical; Escherichia coli Infections; Hemodynamics; Infusions, Intravenous; Injections, Intravenous; Nitric Oxide; Nitroarginine; Random Allocation; Sheep; Shock, Septic