Nurses' preferences regarding MenACWY conjugate vaccines attributes: a discrete choice experiment in Spain.

OBJECTIVES: Immunisation against preventable diseases as meningitis is crucial from a public health perspective to face challenges posed by these infections. Nurses hold a great responsibility for these programs, which highlights the importance of understanding their preferences and needs to improve the success of campaigns. This study aimed to investigate nurses' preferences regarding Meningococcus A, C, W, and Y (MenACWY) conjugate vaccines commercialised in Spain. STUDY DESIGN: A national-level discrete choice experiment (DCE) was conducted. METHODS: A literature review and a focus group informed the DCE design. Six attributes were included: pharmaceutical form, coadministration evidence, shelf-life, package contents, single-doses per package, and package volume. Conditional logit models quantified preferences and relative importance (RI). RESULTS: Thirty experienced primary care nurses participated in this study. Evidence of coadministration with other vaccines was the most important attribute (RI = 43.78%), followed by package size (RI = 22.17%), pharmaceutical form (RI = 19.07%), and package content (RI = 11.80%). There was a preference for evidence of coadministration with routine vaccines (odds ratio [OR] = 2.579, 95% confidence interval [95%CI] = 2.210-3.002), smaller volumes (OR = 1.494, 95%CI = 1.264-1.767), liquid formulations (OR = 1.283, 95%CI = 1.108-1.486) and package contents including only vial/s (OR = 1.283, 95%CI = 1.108-1.486). No statistical evidence was found for the remaining attributes. CONCLUSIONS: Evidence of coadministration with routine vaccines, easy-to-store packages, and fully liquid formulations were drivers of nurses' preferences regarding MenACWY conjugate vaccines. These findings provide valuable insights for decision-makers to optimize current campaigns.

Clinical and economic hospital burden of acute respiratory infection (BARI) due to respiratory syncytial virus in Spanish children, 2015-2018.

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infection (ALRI) in children, causing frequent outpatient visits and hospitalizations. Our study aimed to describe the clinical and direct economic burden of ALRI hospitalizations related to RSV in children in Spain and the characteristics of patients and their episodes. In this retrospective study, ALRI hospitalizations in children aged < 5 years for 2015-2018 were reviewed using anonymized administrative public hospital discharge data from Spain. Three case definitions were considered: (a) RSV-specific; (b) RSV-specific and unspecified acute bronchiolitis (RSV-specific and bronchiolitis); and (c) RSV-specific and unspecified ALRI (RSV-specific and ALRI). The study reported a mean of 36,743 yearly admissions potentially due to RSV, resulting in a mean annual cost of €87.1 million. RSV-specific codes accounted for 39.2% of cases, unspecified acute bronchiolitis for 20.1%, and other unspecified ALRI codes for the remaining 40.6%. The mean hospitalization rate per 1,000 children was 55.5 in the first year of life, 16.0 in the second, and 5.4 between 24 and 59 months. A considerable proportion of cases occurred in children under two years old (> 80.4%) and even during the first year of life (> 61.7%). Otherwise healthy children accounted for 92.9% of hospitalizations and 83.3% of costs during the period. Children born preterm accounted for 1.3% of hospitalizations and 5.7% of costs. The findings revealed that RSV still contributes to a high burden on the Spanish health care system. Children under one year of age and otherwise healthy term infants accounted for most of the substantial clinical and economic burden of RSV. Current evidence potentially underestimates the true epidemiology and burden of severe RSV infection; thus, further studies focusing on the outpatient setting are needed.

Excess hospitalizations and mortality associated with seasonal influenza in Spain, 2008-2018.

BACKGROUND: Influenza may trigger complications, particularly in at-risk groups, potentially leading to hospitalization or death. However, due to lack of routine testing, influenza cases are infrequently coded with influenza-specific diagnosis. Statistical models using influenza activity as an explanatory variable can be used to estimate annual hospitalizations and deaths associated with influenza. Our study aimed to estimate the clinical and economic burden of severe influenza in Spain, considering such models. METHODS: The study comprised ten epidemic seasons (2008/2009-2017/2018) and used two approaches: (i) a direct method of estimating the seasonal influenza hospitalization, based on the number of National Health Service hospitalizations with influenza-specific International Classification of Diseases (ICD) codes (ICD-9: 487-488; ICD-10: J09-J11), as primary or secondary diagnosis; (ii) an indirect method of estimating excess hospitalizations and deaths using broader groups of ICD codes in time-series models, computed for six age groups and four groups of diagnoses: pneumonia or influenza (ICD-9: 480-488, 517.1; ICD-10: J09-J18), respiratory (ICD-9: 460-519; ICD-10: J00-J99), respiratory or cardiovascular (C&R, ICD-9: 390-459, 460-519; ICD-10: I00-I99, J00-J99), and all-cause. Means, excluding the H1N1pdm09 pandemic (2009/2010), are reported in this study. RESULTS: The mean number of hospitalizations with a diagnosis of influenza per season was 13,063, corresponding to 28.1 cases per 100,000 people. The mean direct annual cost of these hospitalizations was €45.7 million, of which 65.7% was generated by patients with comorbidities. Mean annual influenza-associated C&R hospitalizations were estimated at 34,894 (min: 16,546; max: 52,861), corresponding to 75.0 cases per 100,000 (95% confidence interval [CI]: 63.3-86.3) for all ages and 335.3 (95% CI: 293.2-377.5) in patients aged ≥ 65 years. We estimate 3.8 influenza-associated excess C&R hospitalizations for each hospitalization coded with an influenza-specific diagnosis in patients aged ≥ 65 years. The mean direct annual cost of the estimated excess C&R hospitalizations was €142.9 million for all ages and €115.9 million for patients aged ≥ 65 years. Mean annual influenza-associated all-cause mortality per 100,000 people was estimated at 27.7 for all ages. CONCLUSIONS: Results suggest a relevant under-detected burden of influenza mostly in the elderly population, but not neglectable in younger people.

Clinical and economic burden of respiratory syncytial virus in Spanish children: the BARI study.

Respiratory syncytial virus (RSV) infection is a major cause of morbidity in children. However, its disease burden remains poorly understood, particularly outside of the hospital setting. Our study aimed to estimate the burden of medically attended acute lower respiratory infection (ALRI) cases potentially related to RSV in Spanish children. Longitudinal data from September 2017 to June 2018 of 51,292 children aged < 5 years old from the National Healthcare System (NHS) of two Spanish regions were used. Three case definitions were considered: (a) RSV-specific; (b) RSV-specific and unspecified acute bronchiolitis (RSV-specific and Bronchiolitis), and; (c) RSV-specific and unspecified ALRI (RSV-specific and ALRI). A total of 3460 medically attended ALRI cases potentially due to RSV were identified, of which 257 (7.4%), 164 (4.7%), and 3039 (87.8%) coded with RSV-specific, unspecific bronchiolitis, and unspecific ALRI codes, respectively. Medically attended RSV-specific and ALRI cases per 1000 children was 134.4 in the first year of life, 119.4 in the second, and 35.3 between 2 and 5 years old. Most cases were observed in otherwise healthy children (93.1%). Mean direct healthcare cost per medically attended RSV-specific and ALRI case was €1753 in the first year of life, €896 in the second, and €683 between 2 and 5 years old. Hospitalization was the main driver of these costs, accounting for 55.6%, 38.0% and 33.4%, in each respective age group. In RSV-specific cases, mean direct healthcare cost per medically attended case was higher, mostly due to hospitalization: €3362 in the first year of life (72.9% from hospitalizations), €3252 in the second (72.1%), and €3514 between 2 and 5 years old (74.2%). These findings suggest that hospitalization data alone will underestimate the RSV infections requiring medical care, as will relying only on RSV-specific codes. RSV testing and codification must be improved and preventive solutions adopted, to protect all infants, particularly during the first year of life.

Vascular endothelial cell activation by adult Dirofilaria immitis antigens.

Dirofilaria immitis is the causal agent of cardiopulmonary dirofilariosis (heartworm disease). Adult worms lodge in the pulmonary arteries and right ventricle, thus vascular endothelium is exposed to high concentrations of Dirofilaria antigenic products. Heartworm disease habitually develops as a chronic foreseeable pathology. Moreover, the simultaneous death of many adult worms, naturally or induced by a filaricide treatment, can cause acute thromboembolisms and endarteritis. To better understand the effects of the massive death of D. immitis adult worms on the blood vessel endothelium, we cultured vascular endothelial cells in the presence or absence of an antigenic extract of D. immitis adult worms (DiSA). The parasite products increased the expression of enzymes and the synthesis of eicosanoids related to inflammation, such as COX-2, 5-LO, PGE(2) and LTB(4). The expression of ICAM-1 and PECAM-1 adhesion molecules and endothelial and inducible Nitric Oxide Synthases (eNOS and iNOS) was also increased in cultures treated with DiSA. Nevertheless, DiSA decreased endothelial permeability and does not alter both proliferation and apoptosis. These results suggest that the somatic extract of D. immitis adult worms stimulate inflammatory mechanisms in endothelial cells, without altering their basic physiologic processes.

Dirofilaria immitis and Wolbachia-derived antigens: its effect on endothelial mammal cells.

Antigens of both Dirofilaria immitis and Wolbachia symbiont bacteria are implicated in the inflammatory pathology of heartworm infection. The aim of the present study was to compare the stimulatory capacity of in vitro cultures of vascular endothelial cells by the adult somatic antigens of D. immitis (DiSA) and the recombinant form of the Wolbachia surface protein (rWSP), during the first 24h of stimulation. Our results indicate a different stimulatory activity of the two antigens. Both the DiSA and rWSP stimulate the production of the enzymes responsible of the arachidonic acid metabolism, cyclooxygenase-2, 5-lipoxygenase (5-LO), and leukotriene B4. Only DiSA stimulates the production of prostaglandin E2. Related to the adhesion molecules, the DiSA stimulates the expression of intercellular adhesion molecule-1 (ICAM-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1), whereas rWSP stimulates ICAM-1, PECAM-1, and vascular cell adhesion molecule-1 (VCAM-1). Expression of E-cadherin and vascular endothelial growth factor also were stimulated by rWSP. Neither of the two antigens altered the basic physiological mechanisms of endothelial cells, such as cell proliferation, cell cycle, or apoptosis. The biological and pathological significance of these finding are discussed.

Dogs with patent Dirofilaria immitis infection have higher expression of circulating IL-4, IL-10 and iNOS mRNA than those with occult infection.

Dirofilaria immitis is the agent of canine heartworm disease, in which adult worms reside in the pulmonary arteries, producing first stage larvae (microfilariae) that are released into the bloodstream. The present work describes the cytokine and iNOS mRNA expression in the peripheral blood of naturally infected dogs classified as either microfilariemic or amicrofilariemic. Results show that microfilariemic dogs had higher expression of IL-4 and iNOS mRNA than amicrofilariemic dogs. Furthermore, IL-10 mRNA expression was strongly expressed in dogs with circulating microfilariae, compared to only negligible expression in amicrofilariemic dogs. Finally, mf+ status was associated with a predominance in IgG1 production against worm antigens. These results would suggest that circulating mf may stimulate, like in other filarial infections, an immune bias towards unresponsiveness in D. immitis-infected dogs, consenting long-term adult worm survival.

iNOs expression is stimulated by the major surface protein (rWSP) from Wolbachia bacterial endosymbiont of Dirofilaria immitis following subcutaneous injection in mice.

The bacterial endosymbiont Wolbachia of several species of filarial nematodes plays an important role in the inflammatory pathology of filariasis. Nitric oxide (NO) production has also been implicated in the immune response during filarial infections. Here we present data indicating that a recombinant Wolbachia surface protein (rWSP) induces iNOs mRNA expression and NO production, as well as IFN-gamma and a Th1-type antibody response, in inoculated BALB/c mice. This effect is not observed when mice are inoculated with a recombinant heat shock protein from Wolbachia (GroEL).

Changes in the levels of eicosanoids in cats naturally and experimentally infected with Dirofilaria immitis.

Feline heartworm (Dirofilaria immitis) infection is a severe, life-threatening disease. The eicosanoids are lipid mediators derived from the metabolism of the arachidonic acid, involved in the regulation of the immune response and of inflammatory reactions. In this study, naturally infected cats showed significant higher levels of prostaglandin E(2) (PGE2), thromboxane B(2) (TXB(2)) and leukotriene B(4) (LTB4) than uninfected cats. Changes in the levels of eicosanoids during the infection were observed in experimentally infected cats. PGE2 increased significantly during the first 60 days post-infection, then progressively decreased until day 180 post-infection. At this time, PGE2 values are still significantly higher than those observed before the infection. TxB2 and LTB4 increased progressively from the beginning of infection and reached their maximum levels 180 days post-infection. In experimentally infected, ivermectin-treated cats, 15 days after treatment (45 days after infection) both PGE2 and LTB4 levels were similar to those observed in experimentally infected, untreated cats. No significant differences of PGE2 levels were found before the infection and at the end of the experiment (165 days post-treatment, 195 days post-infection). Increased levels of LTB4 were found 15 days post-treatment, afterward they progressively decreased. These data show that D. immitis infection influences the production of intravascular eicosanoids in cats. The high levels of PGE2 observed in the early phase of infection could be related to the survival of the worms, while those of TxB2 and LTB4 detected at the end of the study could mediate the inflammatory reactions and thrombi formation during the feline dirofilariosis.

Immune response to and tissue localization of the Wolbachia surface protein (WSP) in dogs with natural heartworm (Dirofilaria immitis) infection.

Human and animal parasitic filarial nematodes, including the agent of canine and feline heartworm disease Dirofilaria immitis, harbour intracellular bacteria of the genus Wolbachia (Rickettsiaies). It is thought that these bacteria play an important role in the pathogenesis and immune response to filarial infection. Immunoglobulin G (total IgG, IgG1, IgG2) production against and immunohistochemical staining of tissues for the Wolbachia surface protein (WSP) from dogs with natural heartworm infection were evaluated. All infected dogs had significant total anti-WSP IgG levels compared to healthy controls. Interestingly, WSP was recognized by the IgG2 subclass in both microfilariemic dogs and in dogs with no circulating microfilariae (occult infection). However, microfilariemic dogs also produced gG1 antibodies. Positive staining for WSP was observed in lungs, liver and kidneys, in particular in glomerular capillaries of naturally infected dogs who had died from heartworm disease. Our results show for the first time that Wolbachia is recognized specifically by D. immitis--infected dogs and that the bacteria is released into host tissue. Furthermore, microfilariemic status appears to effect immune responses to this endosymbiont.

What is happening outside North America regarding human dirofilariasis?

The etiologic agents of human dirofilariasis in the Old World are Dirofilaria immitis, which cause pulmonary and subcutaneous nodules, and Dirofilaria repens, which cause ocular lesions. Although reports of new cases of dirofilariasis are sporadic in other parts of the world, a considerable amount of information is generated in Europe regarding human dirofilariasis. Most cases have been detected in the Mediterranean countries, Ukraine, and Russia; however, isolated or short series of cases have been reported in the Balkan Republics and central and northern European countries. Seroepidemiologic studies have provided evidence that humans living in endemic areas present rates of infection similar to those of the autochthonous canine populations. Antibodies against endosymbiont Wolbachia bacteria have been demonstrated recently in human Dirofilaria infections. During D. immitis infections, preadult worms and third- and fourth-stage larvae are often destroyed by the host reaction, releasing a considerable amount of Wolbachia, and a Th1-type response against Wolbachia and/or filarial antigens is mounted. On the contrary, infections with D. repens, in which worms frequently remain intact, no Th1-type response has been observed. As humans are resistant hosts, the Th1-response could have a role in the resistance against parasites. The causes for the rise in the incidence of human dirofilariasis as well as the possible application of Wolbachia antigens in the serodiagnosis of human infections are discussed.

Prostaglandin H-synthase-2 is the main enzyme involved in the biosynthesis of octadecanoids from linoleic acid in human dermal fibroblasts stimulated with interleukin-1beta.

This study was focused on the characterization of the metabolism of linoleic acid by human dermal fibroblasts and the effect of interleukin-1 on the biosynthesis of octadecanoids. Dermal fibroblasts untreated and treated with recombinant IL-1beta were incubated with exogenous labeled linoleic acid. A combination of high performance liquid chromatography and gas chromatography-mass spectrometry was used as the analytic technique. We found that dermal fibroblasts convert linoleic acid mainly into 13-hydroxy-9-cis,11-trans-octadecadienoic acid (13-HODE) and 9-hydroxy-10-trans,12-cis-octadecadienoic acid (9-HODE), 13(S)-HODE and 9(R)-HODE being the predominant enantiomers. IL-1beta increased the formation of both 13-HODE and 9-HODE in a concentration-dependent manner with similar EC50 values as for prostanoid formation. This effect of IL-1beta on HODEs formation was concomitant with the expression of prostaglandin H-synthase-2. Formation of octadecanoids was inhibited in a concentration-dependent manner by acetylsalicylic acid and indomethacin. Dexamethasone, actinomycin D, and cycloheximide abolished the effect of IL-1beta on HODEs biosynthesis. Octadecanoid biosynthetic activity was associated with the microsomal fraction. Dermal fibroblasts incorporated [14C]-9-HODE and [14C]-13-HODE into phospholipids, mainly into phosphatidylcholine. IL-1beta increased significantly the esterification of 13-HODE in all glycerophospholipids, the major increase being observed in phosphatidylinositol. These results indicate that prostaglandin H-synthase-2 is the enzyme responsible for the increase in the ability to form HODEs of dermal fibroblasts stimulated with IL-1beta.

The paradoxical vascular interactions between endothelin-1 and calcitonin gene-related peptide in the rat gastric mucosal microcirculation.

1. The interactions between local intra-arterial infusion of endothelin-1 (ET-1) and rat alpha-calcitonin gene-related peptide (alpha-CGRP) on gastric mucosal damage and blood flow have been investigated in the pentobarbitone-anaesthetized rat. 2. Close-arterial infusion of ET-1 (2-200 pmol kg-1 min-1) induced a significant and dose-dependent increase in gastric mucosal haemorrhagic injury. 3. Close-arterial infusion of the higher doses of ET-1 (100 and 200 pmol kg-1 min-1) resulted in a biphasic effect on mucosal blood flow, as determined by laser Doppler flowmetry (LDF). This consisted of an initial transient increase followed by a pronounced and sustained fall in LDF. 4. Local microvascular constriction may thus contribute to the mechanisms underlying the gastric injury induced by these higher doses of ET-1. 5. However, close-arterial infusion of lower doses of ET-1 (2-50 pmol kg-1 min-1), that also provoked substantial mucosal damage, induced only a sustained and significant mucosal hyperaemia, which may be secondary to microvascular injury. 6. Concurrent dose-arterial administration of rat alpha-CGRP (50 pmol kg-1 min-1) significantly inhibited the extent of gastric mucosal injury induced by ET-1 (5 pmol kg-1 min-1). 7. Furthermore, concurrent close-arterial infusion of this dose of alpha-CGRP, which itself increased mucosal LDF, significantly inhibited the hyperaemic response induced by close-arterial infusion of ET-1 (5 pmol kg-1 min-1). 8. These results indicate a damaging action on the gastric mucosa by low doses of ET-1 which is independent of local vasoconstriction, that may involve a direct injury of the microvascular endothelium. The protective action of alpha-CGRP thus seems unlikely to be due to a local vasodilator effect but may reflect protective actions on the microvascular endothelium

The involvement of endothelial dysfunction, nitric oxide and prostanoids in the rat gastric microcirculatory responses to endothelin-1.

1. The role of endothelial dysfunction in the gastric microcirculatory responses during local endothelin-1 (ET-1) infusion has been investigated in the pentobarbitone-anaesthetized rat. Furthermore, the involvement of prostanoids or nitric oxide (NO) in these actions has been investigated by the use of indomethacin to inhibit cyclo-oxygenase and NG-nitro-L-arginine methyl ester (L-NAME) to inhibit NO synthase. 2. Close-arterial infusion of ET-1 (1-10 pmol kg-1 min-1 for 10 min) induced a dose-dependent increase in the gastric leakage of radiolabelled albumin, used as an index of endothelial cell dysfunction. 3. Close-arterial infusion of a submaximal dose of ET-1 (5 pmol kg-1 min-1 for 10 min) significantly increased gastric albumin leakage after 2 min infusion, which reached maximal levels after 10 min, and only slowly declined during the 30 min observation period. 4. By contrast, gastric blood flow, as assessed by laser Doppler flowmetry, did not significantly increase until after 5 min of infusion of ET-1 (5 pmol kg-1 min-1 for 10 min), reaching a maximum after 17 min, and was sustained for the 30 min observation period. 5. Pretreatment with L-NAME (2 mg kg-1, i.v.) or indomethacin (5 mg kg-1, i.v.) significantly reduced both the hyperaemic response to ET-1 and the increase in gastric albumin leakage, and in combination abolished these responses. 6. These results suggest that locally released NO and prostanoids mediate the gastric vasodilator response to close arterial infusion of ET-1. This hyperaemia is preceded by changes in gastric albumin extravasation and hence may be initiated as a response to direct endothelial injury by ET-1.

Interactions between the vascular peptide endothelin-1 and sensory neuropeptides in gastric mucosal injury.

1. The interactions between endogenous and exogenous sensory neuropeptides on gastric mucosal injury induced by endothelin-1 (ET-1) have been investigated in the anaesthetized rat. 2. Close intra-arterial infusion of ET-1 (4-20 pmol kg-1 min-1) dose-dependently induced vasocongestion and haemorrhagic necrosis in the gastric mucosa. 3. Capsaicin-pretreatment, two weeks earlier to deplete sensory neuropeptides from primary afferent neurones, augmented the mucosal damage induced by ET-1, as assessed by both macroscopic and histological examination. 4. The damage induced by threshold doses of ET-1 alone or in capsaicin-pretreated rats was further enhanced by administration of indomethacin (5 mg kg-1, i.v.), indicating a modulatory influence of endogenous prostanoids. 5. Morphine administration (3 mg kg-1, i.v.), which can prevent neuropeptide release, augmented the damage induced by threshold doses of ET-1, this effect being reversed by naloxone (1 mg kg-1, i.v.). 6. Concurrent local intra-arterial infusion of rat alpha-calcitonin gene-related peptide (10-50 pmol kg-1 min-1) dose-dependently reduced the mucosal injury induced by ET-1. 7. These findings suggest interactions between ET-1 and sensory neuropeptides, which may reflect an important influence of these peptide mediators in the regulation of mucosal integrity.

Aminoguanidine-provoked leukocyte adherence to rat mesenteric venules: role of constitutive nitric oxide synthase inhibition.

1. The effects of aminoguanidine on neutrophil adherence to venules and on the diameter of arterioles in the mesenteric vascular bed of the pentobarbitone-anaesthetized rat have been compared with those of the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). 2. Administration of L-NAME (1-10 mg kg-1, i.v.) caused a dose-dependent increase in leukocyte adherence and a reduction in leukocyte rolling velocity in postcapillary venules of the rat mesentery over 1 h. 3. Likewise, aminoguanidine (10-100 mg kg-1, i.v.) dose-dependently increased leukocyte adherence and decreased leukocyte rolling velocity over 1 h. 4. Both L-NAME and aminoguanidine caused a dose-dependent reduction in mesenteric arteriolar diameter and an increase in systemic arterial blood pressure. 5. The effects of aminoguanidine (50 mg kg-1, i.v.) on leukocyte adherence, arteriolar diameter and on blood pressure were significantly reversed by pretreatment with L-arginine (300 mg kg-1, i.v.). 6. These findings indicate that, like L-NAME, aminoguanidine can acutely promote leukocyte adherence to the mesenteric venular wall and reduce arteriolar diameter. Moreover, these acute effects were reversed by L-arginine, suggesting they are mediated through inhibition of constitutive NO synthase.

Regulation of gastric mucosal integrity by endogenous nitric oxide: interactions with prostanoids and sensory neuropeptides in the rat.

1. The interactions between nitric oxide (NO), prostacyclin and sensory neuropeptides in the maintenance of gastric mucosal integrity have been investigated in the anaesthetized rat. 2. Administration of either NG-monomethyl-L-arginine (L-NMMA) to inhibit endothelium-derived NO formation, indomethacin to inhibit prostanoid biosynthesis or chronic capsaicin pretreatment to deplete sensory neuropeptides, did not induce acute mucosal injury. 3. In capsaicin-pretreated rats, however, L-NMMA (12.5-100 mg kg-1 i.v.) dose-dependently induced acute mucosal damage, characterized as vasocongestion and haemorrhagic necrosis. The enatiomer D-NMMA (100 mg kg-1 i.v.) did not induce any detectable mucosal damage. 4. This mucosal injury induced by L-NMMA was inhibited by concurrent administration of L-arginine (300 mg kg-1 i.v.). 5. In indomethacin (5 mg kg-1 i.v.)-pretreated rats, L-NMMA also induced mucosal damage. Furthermore, following indomethacin administration in capsaicin-pretreated rats, L-NMMA induced widespread, severe haemorrhagic necrotic damage. 6. These findings suggest a role for endogenous NO formed from L-arginine, acting in concert with prostacyclin and sensory neuropeptides, in the modulation of gastric mucosal integrity.

The actions of nitric oxide donors in the prevention or induction of injury to the rat gastric mucosa.

1. The protective or damaging actions on the gastric mucosa, of locally infused nitrovasodilators that donate nitric oxide (NO), have been investigated in the pentobarbitone-anaesthetized rat. 2. Local intra-arterial infusion of endothelin-1 (ET-1; 5 pmol kg-1 min-1 for 10 min) induced extensive, macroscopically apparent, haemorrhagic injury to the rat gastric mucosa. This damage was dose-dependently reduced by concurrent local intra-arterial infusion of glyceryl trinitrate (GTN; 10-40 micrograms kg-1 min-1) which liberates NO on metabolic transformation, or the nitrosothiol, S-nitroso-N-acetyl-penicillamine (SNAP, 2.5-10 micrograms kg-1 min-1) which spontaneously liberates NO. 3. Local infusion of higher doses of SNAP (20 and 40 micrograms kg-1 min-1, i.a.) did not, however, significantly protect against mucosal injury induced by ET-1. 4. Furthermore, local infusion alone of these higher doses of SNAP, as well as sodium nitroprusside (10-40 micrograms kg-1 min-1, i.a.) which also spontaneously liberates NO, induced significant mucosal injury, as assessed macroscopically and confirmed by histology. 5. Local infusion of these higher doses of SNAP and nitroprusside reduced systemic arterial blood pressure (BP), but this was not correlated with the extent of mucosal injury. 6. Furthermore, local infusion of GTN (10-40 micrograms kg-1 min-1, i.a.) alone, which also reduced BP, failed to induce gastric mucosal damage. 7. These findings suggest that exogenous NO can protect the rat gastric mucosa from damage induced by the vasoconstrictor peptide ET-1, which may reflect local microcirculatory interactions. However, the unregulated release of high levels of NO within the microvasculature induces mucosal injury.

Modulation of the vasodepressor actions of acetylcholine, bradykinin, substance P and endothelin in the rat by a specific inhibitor of nitric oxide formation.

1. The effects of the specific inhibitor of nitric oxide (NO) formation, NG-monomethyl-L-arginine (L-NMMA), on resting systemic arterial blood pressure (BP) and on the actions of both endothelium-dependent and endothelium-independent vasodilators were investigated in the anaesthetized, normotensive rat. 2. Intravenous administration of L-NMMA (12.5-50 mg kg-1; 47-188 mumol kg-1) but not its enantiomer, D-NMMA, induced a dose-related increase in BP, which was reversed by the intravenous administration of L-arginine (150-600 mumol kg-1), but not D-arginine. 3. The vasodepressor responses to intravenous administration of the endothelium-dependent vasodilators, acetylcholine, bradykinin and substance P were significantly inhibited by L-NMMA (94 and 188 mumol kg-1 i.v.), but not by D-NMMA. 4. The inhibition by L-NMMA of these vasodepressor responses was reversed by administration of L-arginine, but not D-arginine. 5. Endothelin (ET-1) induced dose-related vasodepressor responses following bolus intravenous administration, which were significantly inhibited by L-NMMA but not by D-NMMA. This inhibition was reversed by administration of L-arginine. 6. The vasodepressor effects of the endothelium-independent vasodilators, glyceryl trinitrate or prostacyclin, were not significantly inhibited by L-NMMA. 7. These findings with L-NMMA suggest that resting blood pressure in the rat is modulated by endogenous NO biosynthesis and that endothelium-dependent vasodilators act through the formation of endogenous NO to exert their actions in vivo.