Intestinal nitric oxide in the normal and endotoxemic pig

Estimation of Nitrite-Nitric Oxide Derivative-In Horses with Intestinal Colic by ESR Spectroscopy

Diseases of the gastrointestinal tract of horses are caused by many factors and have a complex pathogenesis. Developing effective methods of differential diagnostics is of high fundamental and applied importance. The pathogenesis of diseases of the digestive tract of horses accompanied by the development of inflammation and oxidative stress, can be associated with a lack of the nitrogen monoxide which controls many signaling pathways in the body. The level of the nitric oxide (NO) is involved in the regulation of the immune and nervous systems, the tone of all the blood vessels, and the courses of many pathological processes. The nitric oxide activates guanylate cyclase (sGC) and leads to vascular relaxation. The aim of this investigation was to study the metabolites of nitric oxide in horses suffered from intestinal diseases. The levels of nitric oxide in the blood serum of horses depending on their age and health state was studied. The concentration of nitrites in the blood serum of horses aged 6–25 years was 3.4 ± 4.2 μM, and in the young horses (1–5 years) the level of this indicator was 8.2 ± 5.4 μM. A sharp decrease in nitrite was observed in all the horses with intestinal diseases of 2 ± 0.9 μM, especially with tympanitic caecun of 0.6 ± 0.4 μM and with spasmodic colic of 1.8 ± 0.5 μM. The level of nitrosylhemoglobin HbNO in the blood of the diseased animals was higher than that in clinically healthy horses, regardless of age.

Effect of Shuwei Decoction () on rats with functional dyspepsia

OBJECTIVE

To investigate the effects of Shuwei Decoction (, SWD) on gastric emptying, serum stem cell factor (SCF), the content of serum nitric oxide (NO), and structure change of interstitial cells of Cajal (ICC) in functional dyspepsia (FD) rats.

METHODS

Sixty Sprague Dawley rats were randomly divided into 6 groups: blank group (group A), model group (group B), mosapride group (group C), Muxiang Shunqi Pill (, MSP) group (group D), SWD low-dose group (group E), and SWD high-dose group (group F), 10 rats in each group. FD rat model was established by clasping rats' tails for 7 days, except the group A. After 3 days, group A and group B were given distilled water, and the medicated rats were given corresponding medicine for 14 days. The gastric emptying, structure change of ICC in gastric antrum by transmission electron microscope, the content of serum NO by nitrate reductant and SCF by enzyme linked immunosorbent assay were observed.

RESULTS

Compared with group A, the rats in group B delayed gastric emptying, serum SCF decreased, serum NO increased (P <0.05). Compared with group B, the rats in groups D, E and F were improved on gastric emptying, obviously increased on serum SCF, decreased on serum NO (P <0.05), and structure change of ICC in gastric antrum improved. Compared with group B, structure change of ICC of group E after treatment was improved and was closed to group A.

CONCLUSION

SWD recovered gastrointestinal motility of FD, possibly by regulating the levels of serum NO and SCF, and improving the structure of ICC in gastric antrum.

Effects of nitric oxide in 5-hydroxytryptamine-, cholera toxin-, enterotoxigenic Escherichia coli- and Salmonella Typhimurium-induced secretion in the porcine small intestine

The effects of nitric oxide (NO) in the secretory response to the endogenous secretagogue 5-hydroxytryptamine (5-HT), the enterotoxins heat-labile enterotoxigenic Escherichia coli (ETEC) toxin (LT) and cholera toxin (CT), and various cultures of ETEC and Salmonella serotype Typhimurium in the porcine small intestine (Sus scrofa) were investigated. In anaesthetized pigs, jejunal tied-off loops were instilled with 5-HT, LT, CT, various cultures of ETEC or S. Typhimurium. Pigs were given intravenously isotonic saline or isotonic saline containing the NO synthase inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME). L-NAME significantly induced an increased fluid accumulation in loops induced by 5-HT, ETEC and stn-mutated S. Typhimurium. Fluid accumulation in loops instilled with wild-type S. Typhimurium was increased by L-NAME, although not significantly, while there was no effect on fluid accumulation induced by an invH-mutated isogenic strain. No significant effect of L-NAME was observed on the fluid accumulation induced by the purified enterotoxins LT and CT. The results also demonstrated a relatively large difference in the ability to induce fluid accumulation between the bacteria strains. Diastolic, systolic and mean blood pressures were significantly increased and the body temperature was significantly decreased in groups of pigs treated with L-NAME. In conclusion, the results suggest that NO has a proabsorptive effect in the intact porcine jejunum and is involved in the systemic vascular tone.

Nitric oxide synthase inhibition in sepsis? Lessons learned from large-animal studies

Nitric Oxide (NO) plays a controversial role in the pathophysiology of sepsis and septic shock. Its vasodilatory effects are well known, but it also has pro- and antiinflammatory properties, assumes crucial importance in antimicrobial host defense, may act as an oxidant as well as an antioxidant, and is said to be a "vital poison" for the immune and inflammatory network. Large amounts of NO and peroxynitrite are responsible for hypotension, vasoplegia, cellular suffocation, apoptosis, lactic acidosis, and ultimately multiorgan failure. Therefore, NO synthase (NOS) inhibitors were developed to reverse the deleterious effects of NO. Studies using these compounds have not met with uniform success however, and a trial using the nonselective NOS inhibitor N(G)-methyl-l-arginine hydrochloride was terminated prematurely because of increased mortality in the treatment arm despite improved shock resolution. Thus, the issue of NOS inhibition in sepsis remains a matter of debate. Several publications have emphasized the differences concerning clinical applicability of data obtained from unresuscitated, hypodynamic rodent models using a pretreatment approach versus resuscitated, hyperdynamic models in high-order species using posttreatment approaches. Therefore, the present review focuses on clinically relevant large-animal studies of endotoxin or living bacteria-induced, hyperdynamic models of sepsis that integrate standard day-to-day care resuscitative measures.

Sepsis: an arginine deficiency state?

OBJECTIVE

Sepsis is a major health problem considering its significant morbidity and mortality rate. The amino acid L-arginine has recently received substantial attention in relation to human sepsis. However, knowledge of arginine metabolism during sepsis is limited. Therefore, we reviewed the current knowledge about arginine metabolism in sepsis.

DATA SOURCE

This review summarizes the literature on arginine metabolism both in general and in relation to sepsis. Moreover, arginine-related therapies are reviewed and discussed, which includes therapies of both nitric oxide (NO) and arginine administration and therapies directed toward inhibition of NO.

DATA

In sepsis, protein breakdown is increased, which is a key process to maintain arginine delivery, because both endogenous de novo production from citrulline and food intake are reduced. Arginine catabolism, on the other hand, is markedly increased by enhanced use of arginine in the arginase and NO pathways. As a result, lowered plasma arginine levels are usually found. Clinical symptoms of sepsis that are related to changes in arginine metabolism are mainly related to hemodynamic alterations and diminished microcirculation. NO administration and arginine supplementation as a monotherapy demonstrated beneficial effects, whereas nonselective NO synthase inhibition seemed not to be beneficial, and selective NO synthase 2 inhibition was not beneficial overall.

CONCLUSIONS

Because sepsis has all the characteristics of an arginine-deficiency state, we hypothesise that arginine supplementation is a logical option in the treatment of sepsis. This is supported by substantial experimental and clinical data on NO donors and NO inhibitors. However, further evidence is required to prove our hypothesis.

Gastrointestinal nitric oxide generation in germ-free and conventional rats

Nitric oxide (NO) is a central mediator of various physiological events in the gastrointestinal tract. The influence of the intestinal microflora for NO production in the gut is unknown. Bacteria could contribute to this production either by stimulating the mucosa to produce NO, or they could generate NO themselves. Using germ-free and conventional rats, we measured gaseous NO directly in the gastrointestinal tract and from the luminal contents using a chemiluminescence technique. Mucosal NO production was studied by using an NO synthase (NOS) inhibitor, and to evaluate microbial contribution to the NO generation, nitrate was given to the animals. In conventional rats, luminal NO differed profoundly along the gastrointestinal tract with the greatest concentrations in the stomach [>4,000 parts per billion (ppb)] and cecum (approximately 200 ppb) and lower concentrations in the small intestine and colon (< or =20 ppb). Cecal NO correlated with the levels in incubated luminal contents. NOS inhibition lowered NO levels in the colon, without affecting NO in the stomach and in the cecum. Gastric NO increased greatly after a nitrate load, proving it to be a substrate for NO generation. In germ-free rats, NO was low (< or =30 ppb) throughout the gastrointestinal tract and absent in the incubated luminal contents. NO also remained low after a nitrate load. Our results demonstrate a pivotal role of the intestinal microflora in gastrointestinal NO generation. Distinctly compartmentalized qualitative and quantitative NO levels in conventional and germ-free rats reflect complex host microbial cross talks, possibly making NO a regulator of the intestinal eco system.

Novel endothelin receptor antagonist attenuates endotoxin-induced lung injury in sheep

OBJECTIVE

To evaluate the cardiopulmonary effects of the novel endothelin receptor antagonist tezosentan in endotoxin-induced lung injury in sheep and to assess the dose response to tezosentan and endothelin-1 in healthy sheep.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

University animal laboratory.

SUBJECTS

Twenty-one yearling sheep.

INTERVENTIONS

Seventeen awake, chronically instrumented sheep were subjected to intravenous infusion of Ringer's lactate for 24 hrs. The animals were randomly assigned to a sham-operated group (n = 3), a lipopolysaccharide group (n = 7) receiving an intravenous infusion of Escherichia coli lipopolysaccharide 15 ng x kg x min, and a tezosentan group (n = 7) subjected to lipopolysaccharide and, from 4 hrs, an intravenous injection of tezosentan 3 mg/kg followed by infusion of 1 mg x kg x hr. In addition, four healthy sheep, exposed to an intravenous infusion of endothelin-1 at 20 ng x kg x min, after 1 hr received tezosentan in stepwise increasing doses of 0.5, 1, and 2 mg x kg x hr that were maintained for 1 hr each. After a 4-hr recovery, the sheep received infusions of tezosentan at the same dose rates as a pretreatment to endothelin-1.

MEASUREMENTS AND MAIN RESULTS

In the sham-operated sheep, all cardiopulmonary variables remained unchanged. Lipopolysaccharide caused pulmonary hypertension, increased extravascular lung water index, and induced arterial hypoxemia. Tezosentan decreased the increments in pulmonary vascular resistance and extravascular lung water index by as much as 60% and 70%, respectively. In parallel, tezosentan ameliorated arterial hypoxemia, increased cardiac index, attenuated the decrease in stroke volume index, and reduced systemic vascular resistance. Compared with the lipopolysaccharide group, tezosentan further increased plasma concentrations of endothelin-1. In healthy animals, the administration of endothelin-1 induced systemic and pulmonary hypertension, increased extravascular lung water index, and evoked bradycardia and a decrease in cardiac index. These changes were attenuated by tezosentan infused at 1 and 2 mg x kg x hr.

CONCLUSIONS

In an ovine model of endotoxin-induced lung injury, tezosentan ameliorates pulmonary hypertension, lung edema, cardiac dysfunction, and arterial hypoxemia. Tezosentan counteracts the hemodynamic effects of endothelin-1 in a dose-dependent manner.

Effect of intravenous L-NMMA on nitric oxide production in collagenous colitis

BACKGROUND

Nitric oxide (NO) is greatly increased in the colon of patients with inflammatory bowel disease of different aetiology, including collagenous colitis. In man, NO can be generated from NO synthases as well as from non-enzymatic sources. The source of the NO found in luminal intestinal gas has not been exactly pinpointed. We investigated the effect of the NO synthase inhibitor L-NMMA on intestinal concentrations of NO in patients with clinically active collagenous colitis. In addition, we measured NO levels from the respiratory tract.

METHODS

Ten patients with active collagenous colitis were studied. NO levels were measured from the respiratory tract and in the rectum before and after i.v. administration of L-NMMA (7.5 mg/kg) using a chemiluminescence method.

RESULTS

Airway NO release decreased markedly, and mean arterial blood pressure increased in all patients following L-NMMA treatment. Basal rectal NO levels were high (median > 10000 ppb) and decreased markedly in 5 patients after L-NMMA. In contrast, NO levels remained completely unchanged or even increased in the other 5 patients.

CONCLUSION

Rectal levels of NO are greatly increased in patients with symptomatic collagenous colitis. Intravenous administration of an NO synthase inhibitor reduced rectal NO only in half of the patients despite clear evidence of effective systemic NO synthase inhibition. This could indicate alternative NOS-independent sources of intestinal NO in this disease.

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