nitroarginine and Sepsis

Impaired vascular responsiveness in sepsis may lead to maldistribution of blood flow in organs. We hypothesized that increased production of nitric oxide (NO) via inducible nitric oxide synthase (iNOS) mediates the impaired dilation to ACh in sepsis. Using a 24-h cecal ligation and perforation (CLP) model of sepsis, we measured changes in arteriolar diameter and in red blood cell velocity (V(RBC)) in a capillary fed by the arteriole, following application of ACh to terminal arterioles of rat hindlimb muscle. Sepsis attenuated both ACh-stimulated dilation and V(RBC) increase. In control rats, arteriolar pretreatment with the NO donors S-nitroso-N-acetylpenicillamine or sodium nitroprusside reduced diameter and V(RBC) responses to a level that mimicked sepsis. In septic rats, arteriolar pretreatment with the "selective" iNOS blockers aminoguanidine (AG) or S-methylisothiourea sulfate (SMT) restored the responses to the control level. The putative neuronal NOS (nNOS) inhibitor 7-nitroindazole also restored the response toward control. At 24-h post-CLP, muscles showed no reduction of endothelial NOS (eNOS), elevation of nNOS, and, surprisingly, no induction of iNOS protein; calcium-dependent constitutive NOS (eNOS+nNOS) enzyme activity was increased whereas calcium-independent iNOS activity was negligible. We conclude that 1) AG and SMT inhibit nNOS activity in septic skeletal muscle, 2) NO could impair vasodilative responses in control and septic rats, and 3) the source of increased endogenous NO in septic muscle is likely upregulated nNOS rather than iNOS. Thus agents released from the blood vessel milieu (e.g., NO produced by skeletal muscle nNOS) could affect vascular responsiveness.

Topics: Acetylcholine; Animals; Arterioles; Enzyme Inhibitors; Lactic Acid; Male; Muscle, Skeletal; Necrosis; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitrites; Nitroarginine; Nitroprusside; Penicillamine; Rats; Rats, Sprague-Dawley; Sepsis; Vasodilation

The cecal ligation and puncture (CLP) model was used to investigate whether failure of neutrophil migration occurs in sepsis and whether it correlates with disease outcome. It was observed that the severity of sepsis correlates with the number of punctures in the cecum: mice with 2 punctures (sublethal [SL]-CLP) developed mild peritonitis (100% survived), whereas mice with 12 punctures (lethal [L]-CLP) developed severe peritonitis and bacteremia that evolved to sepsis (none survived). The production of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-10 was higher in L-CLP than in SL-CLP mice. The impairment of neutrophil migration to the peritoneum and to the cecum wall was observed only in L-CLP mice. This phenomenon was shown to be mediated by nitric oxide, because aminoguanidine prevented the failure of neutrophil migration and improved the survival of L-CLP animals. In conclusion, impairment of neutrophil migration is a crucial event in the worsening of sepsis, and nitric oxide seems to be responsible for the phenomenon.

Topics: Animals; Ascitic Fluid; Bacteremia; Cell Movement; Colony Count, Microbial; Cytokines; Disease Models, Animal; Enzyme Inhibitors; Guanidines; Heart; Liver; Lung; Male; Mice; Mice, Inbred C57BL; Neutrophils; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Peritoneal Cavity; Peritoneal Diseases; Sepsis; Wounds, Penetrating

Nitric oxide (NO) is an important physiological mediator of vascular tone and is involved in pathophysiology of septic shock. Although plasma nitrite is a stable end product of NO oxidation derived from endogenous NO, the plasma nitrite level is also easily affected by the intake of various foods, bacterial products and renal functional status.. We propose an excellent alternative assay technique for measuring endogenous NO production.. We measured the nitrite level in cultured vascular smooth muscle cells (SMC) treated with serum obtained from patients with sepsis (4 patients), by means of a chemiluminescence detector.. The nitrite concentrations in such cells were significantly higher as compared to those in the cells treated with normal serum. Moreover, the increased nitrite levels in the SMC treated with the sera obtained from patients with sepsis were completely inhibited by L-nitroarginine (1 mmol/L), a nitric oxide synthase inhibitor.. These data suggest that this assay method enable us to know the ability of endogenous NO production in each patient.

Topics: Aged; Animals; Cattle; Cells, Cultured; Enzyme Inhibitors; Female; Humans; Male; Middle Aged; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Sepsis

Inhibitors of nitric oxide (NO) synthesis have been used in the treatment of septic and endotoxic shock. However, several studies question the beneficial effect of inhibiting NO production in sepsis and endotoxemia. We have investigated the effect of inhibition of NO synthesis after endotoxemia in the isolated perfused rat heart. In hearts from endotoxin-treated animals, coronary flow was elevated 64% and oxygen consumption was elevated 20% compared with control hearts. NADH fluorescence imaging was used as an indicator of regional hypoperfusion. A homogeneous low-surface NADH fluorescence, indicative of adequate tissue perfusion, was observed in both control and endotoxin-treated hearts. The increase in coronary flow and oxygen consumption could only partially be prevented by pretreatment of the animals with dexamethasone. Addition of N omega-nitro-L-arginine (NNLA), an inhibitor of NO synthesis, to the perfusion medium eliminated differences in coronary flow and oxygen consumption between normal and endotoxin-treated hearts. However, NADH surface fluorescence images of endotoxin-treated hearts after NNLA revealed areas of high fluorescence, indicating local ischemia, whereas the control hearts remained without signs of ischemia. The ischemic areas were present at various perfusion pressures and disappeared after the infusion of L-arginine, the natural precursor of NO, or the exogenous NO donor sodium nitroprusside. Methylene blue (MB), an inhibitor of soluble guanylate cyclase, the effector enzyme of NO, also eliminated differences in coronary flow and produced similar areas of local myocardial ischemia in endotoxin-treated hearts but not in control hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Coronary Circulation; Dexamethasone; Endotoxins; Male; Methylene Blue; Myocardial Ischemia; NAD; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxygen Consumption; Rats; Rats, Wistar; Sepsis; Vasopressins

To determine the effects of the inhibition of endothelium-derived relaxation factor in an animal model of neonatal group B streptococcal sepsis.. Comparison of three experimental protocols: a) N-nitro-L-arginine; b) group B streptococcal; and c) group B streptococcal/N-nitro-L-arginine.. Piglets, 1 to 2 wks old.. Endothelium-derived relaxation factor inhibition was produced in nonseptic piglets by the infusion of a competitive inhibitor of nitric oxide synthase, N-nitro-L-arginine, at 30 mg/kg (N-nitro-L-arginine protocol; n = 6). Human group B streptococcal sepsis was modeled in piglets by the continuous infusion of live group B streptococcal organisms at approximately 5 x 10(9) organisms/kg cumulative dose (group B streptococcal protocol; n = 8). Endothelium-derived relaxation factor inhibition during a group B streptococcal sepsis was produced by N-nitro-L-arginine infusion during continuing group B streptococcal infusion (group B streptococcal/N-nitro-L-arginine protocol; n = 7).. Both N-nitro-L-arginine and group B streptococcal infusion significantly increased systemic and pulmonary vascular resistance and decreased cardiac output and oxygen delivery. N-nitro-L-arginine differed from group B streptococcal infusions in its effects on systemic blood pressure (BP) (N-nitro-L-arginine increased BP while group B streptococcal infusions did not), and pulmonary/systemic vascular resistance ratio (group B streptococcal infusions increased pulmonary/systemic vascular resistance ratio more than N-nitro-L-arginine did). The group B streptococcal/N-nitro-L-arginine group differed significantly from piglets receiving continued group B streptococcal infusion without N-nitro-L-arginine in cardiac output (significantly lower in group B streptococcal/N-nitro-L-arginine), oxygen delivery (significantly lower in group B streptococcal/N-nitro-L-arginine), and pulmonary vascular resistance (significantly higher in group B streptococcal/N-nitro-L-arginine).. Group B streptococcal sepsis in human newborns and in animal models of human newborns is characterized by a hemodynamic constellation of "cold shock"--increased vascular resistance and reduced systemic blood flow. Endothelium-derived relaxation factor inhibition during group B streptococcal sepsis in piglets exacerbated many of the adverse hemodynamic consequences of group B streptococcal infusion. We speculate that endothelium-derived relaxation factor inhibition has no foreseeable therapeutic role in neonatal septic shock.

Topics: Animals; Animals, Newborn; Arginine; Blood Pressure; Cardiac Output; Hemodynamics; Nitric Oxide; Nitroarginine; Oxygen Consumption; Pulmonary Circulation; Sepsis; Streptococcal Infections; Streptococcus agalactiae; Swine; Vascular Resistance

We examined vascular reactivity to vasoconstrictors [phenylephrine (PE), serotonin (5-HT), and high K+] and vasodilators [acetylcholine (ACh), A23187, L-arginine, and nitroglycerin (NTG)] in isolated mesenteric arterial rings from control and septic rats. Sepsis was induced by cecal ligation and puncture (CLP). A possible mechanism underlying CLP-induced alteration in vascular reactivity was also investigated with N omega-nitro-L-arginine (L-NNA 50 microM), methylene blue (MB 10 microM), and indomethacin (5 microM). In vivo, septic rats manifested two distinct hemodynamic phases, a hyperdynamic state during early (9 h after CLP) phase, followed by a hypodynamic state during late (18 h after CLP) phase. Therefore, we examined ex vivo vascular reactivity in these two phases. Results demonstrated that CLP operation caused hyporesponsiveness to contractile agents and hyperresponsiveness to vasodilator agents. After endothelium removal, most of the contractile responses were enhanced in both CLP-operated (9 and 18 h after operation) and sham-operated rats, whereas enhancement of high-K(+)-induced contraction was observed only in denuded rings from CLP 18-h rats. In addition, augmentation of relaxation induced by ACh at 9 or 18 h after CLP was abolished by N omega-nitro-L-arginine or MB but not by indomethacin. A possible mechanism responsible for alterations of vascular reactivity may be overproduction of nitric oxide (NO) which is blocked by L-NNA or MB.

Topics: Animals; Arginine; Blood Glucose; Blood Pressure; Body Temperature; Cecum; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Heart Rate; In Vitro Techniques; Indomethacin; Male; Methylene Blue; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Nitroarginine; Rats; Rats, Sprague-Dawley; Sepsis; Vascular Resistance; Vasoconstrictor Agents; Vasodilator Agents

To investigate the role of nitric oxide in the regulation of vascular tone in patients with the sepsis syndrome.. Prospective, intervention study.. Tertiary care hospital.. Fifteen patients admitted to our medical intensive care unit with the diagnosis of sepsis syndrome by defined criteria.. Eight patients received N omega-nitro-L-arginine (20 mg/kg, iv bolus) followed by L-arginine (200 mg/kg, iv bolus). Seven patients received L-arginine alone (200 mg/kg).. In the first group, hemodynamic and oxygen transport variables were recorded at baseline, during 45 mins after the injection of N omega-nitro-L-arginine, and during 45 mins after the administration of L-arginine. In the second group, hemodynamic parameters were recorded at baseline and during 15 mins after the administration of L-arginine. Data are mean +/- SEM. The administration of N omega-nitro-L-arginine was followed by hypertension (mean blood pressure increased from 89 +/- 8 to a maximum of 140 +/- 12 mm Hg) accompanied by a decrease in cardiac index (from 3.51 +/- 0.39 to a minimum of 2.65 +/- 0.21 L/min/m2) and an increase in right atrial and pulmonary artery occlusion pressure. Systemic vascular resistance index increased from 1871.1 +/- 302.3 to 3825.6 +/- 244.4 dyne.sec/cm5.m2, and pulmonary vascular resistance increased from 533.2 +/- 125.8 to 816.0 +/- 117.3 dyne.sec/cm5.m2. These changes induced by N omega-nitro-L-arginine were reversed by the administration of L-arginine. The administration of L-arginine to another group of patients caused transient hypotension (from 103 +/- 6 to 81 +/- 10 mm Hg) and an increase in cardiac index (from 3.57 +/- 0.15 to 4.74 +/- 0.54 L/min/m2). Both systemic and pulmonary vascular resistance indices decreased (from 1987.6 +/- 163.9 to 1251.4 +/- 231.5 dyne.sec/cm5.m2, and from 486.1 +/- 65.2 to 380.5 +/- 70.3 dyne.sec/cm5.m2). Parallel to the increase in oxygen transport due to the increase in cardiac output, oxygen consumption index increased significantly 1 min after L-arginine (from 127.0 +/- 19.0 to 182.5 +/- 37.3 mL/min/m2). All mentioned changes were statistically significant (p < .05).. A continuous basal release of nitric oxide plays a role in the regulation of systemic and pulmonary vascular tone in patients with sepsis syndrome. L-arginine has systemic and pulmonary vasodilatory actions.

Topics: Aged; Aged, 80 and over; Arginine; Drug Therapy, Combination; Female; Hemodynamics; Humans; Injections, Intravenous; Male; Middle Aged; Nitric Oxide; Nitroarginine; Oxygen Consumption; Prospective Studies; Pulmonary Circulation; Respiratory Transport; Sepsis