7-nitroindazole, but not L-NAME or aminoguanidine, attenuates anaphylactic hypotension in conscious rats

The roles of NO and isozymes of NO synthase (NOS) are not known in anaphylactic hypotension of unanesthetized rats. Effects of inhibition of NOS, iNOS, and nNOS by N-nitro-L-arginine methyl ester (L-NAME), aminoguanidine, and 7-nitroindazole, respectively, were determined on the antigen-induced systemic hypotension and portal hypertension in conscious Sprague-Dawley rats sensitized with the ovalbumin antigen. The MAP and portal venous pressure were directly and simultaneously measured. The control rats showed a decrease in MAP along with an increase in portal venous pressure but did not die within 48 h after antigen injection. In the rats pretreated with the nonselective NOS inhibitor L-NAME (10 mg/kg), MAP before and after antigen administration was significantly higher than that of the control rats, but the net decrease in MAP and increase in portal venous pressure were rather greater than those of the control, resulting in fatal outcome within 12 h after antigen administration. In contrast, pretreatment with the relatively selective nNOS inhibitor 7-nitroindazole (50 mg/kg) substantially attenuated anaphylactic hypotension over 20 min after antigen administration, whereas the relatively selective iNOS inhibitor aminoguanidine (100 mg/kg) did not affect it. In conclusion, in anaphylactic hypotension of unanesthetized rats, NO derived from nNOS, but not from iNOS, may be involved, and the nonselective NOS inhibitor L-NAME is lethal.     

Roles of nitric oxide synthases in platelet-activating factor-induced intestinal necrosis in rats

OBJECTIVE: To examine the role of constitutive and inducible nitric oxide synthases (cNOS and iNOS) in platelet-activating factor (PAF)-induced shock and intestinal injury. DESIGN: Prospective, randomized, controlled experimental study. SETTING: Hospital research laboratory. SUBJECTS: Young adult male Sprague-Dawley rats were anesthetized and studied. INTERVENTIONS: Rats were injected with PAF, either alone or after the following pretreatments: a) selective iNOS inhibitors aminoguanidine or S-methylisothiourea; b) 3-morpholinosydnonimine, a NO donor; c) S-methylisothiourea + 3-morpholinosydnonimine; and d) antineutrophil antibody (to deplete neutrophils). MEASUREMENTS AND MAIN RESULTS: Blood pressure, hematocrit, white blood cell counts, intestinal injury, and intestinal cNOS and iNOS activities were assessed. We found that: a) cNOS is the predominant NOS in the intestine and its activity is inversely correlated to the level of tissue injury; b) there is a time-dependent increase in cNOS activity in sham-operated animals, which was abolished by PAF; c) Western blotting and immunohistochemistry showed iNOS present in the normal intestine, localizing mainly in crypt cells; d) iNOS inhibitors attenuated PAF-induced injury in animals with high cNOS activity, but had no protective effect in animals with low cNOS activity; e) 3-morpholinosydnonimine, alone or together with S-methylisothiourea, alleviated PAF-induced injury; and f) neutrophil depletion blocked the suppressive effect of PAF on cNOS and prevented injury. CONCLUSIONS: We conclude that cNOS and iNOS play different roles in PAF-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of iNOS inhibitors.     

Beneficial effects of TCV-309, a novel potent and selective platelet activating factor antagonist in endotoxin and anaphylactic shock in rodents.

Pharmacological profiles of a novel specific platelet activating factor (PAF) antagonist, TCV-309 (3-bromo-5-[N-phenyl-N-[2-[2- (1,2,3,4-tetrahydro-2-isoquinolycarbonyloxy)ethyl] carbamoyl]ethyl] carbamoyl]-1-propylpyridinium nitrate] and its beneficial effects in shock were examined. TCV-309 specifically inhibited PAF-induced aggregation of rabbit and human platelets, and [3H]PAF binding to rabbit platelet microsomes with IC50 values of 33, 58 and 27 nM, respectively. It was as potent as WEB 2086 and more potent than CV-6209 and CV-3988. TCV-309 did not cause hemolysis in human or rat blood due to a detergent-like action. In rats, TCV-309 selectively inhibited the PAF-induced hypotension, hemoconcentration and death with ED50 values of 2.7, 6.4 and 1.7 micrograms/kg (i.v.), respectively. TCV-309 most potently protected mice from death induced by PAF and due to anaphylactic shock with ED50 values of 2.1 and 2.6 micrograms/kg (i.v.), respectively, when compared with CV-3988, CV-6209, WEB 2086 (i.v.) and L-652731 (p.o.). TCV-309 also reversed PAF-induced hypotension and endotoxin-induced hypotension in rats with ED50 values of 3.3 and 1.2 micrograms/kg (i.v.), respectively. There was a significant linear relationship between the ability (ED50 value) of these PAF antagonists to prevent death induced by PAF and death due to anaphylactic shock in mice, and between their reversing ability (ED50 value) for the hypotension induced by PAF and endotoxin in rats. TCV-309 (100 micrograms/kg i.v.) protected rats from death induced by endotoxin. Thus, PAF may be a lethal mediator in anaphylactic shock and a hypotensive mediator in endotoxin shock in rodents.     

Pharmacological actions of PCA 4248, a new platelet-activating factor receptor antagonist: in vivo studies

The ability of PCA 4248 [2-(phenylthio)ethyl-5-methoxycarbonyl- 2,4,6-trimethyl-1,4-dihydropyridine-3-carboxylate] to block PAF-induced systemic hypotension and protein-rich plasma extravasation in rats, and PAF-induced death in mice, was tested. These studies were complemented with experiments using soluble aggregates of immunoglobulin G (A-IgG), bacterial endotoxin and the cytokine tumor necrosis factor as putative inducers of the generation of endogenous PAF. Significant inhibition of PAF-induced systemic hypotension was observed with i.v. PCA 4248 at doses of 0.3 to 1 mg/kg (IC50 value, 0.45 mg/kg, with PAF 0.33 micrograms/kg). Reversal of the hypotension was rapidly observed when PCA 4248 was administered after PAF. The extravasation induced by 1 microgram/kg PAF was also blocked by PCA 4248 (IC50 value, 0.36 mg/kg). Inhibition of the extravasation induced by A-IgG and endotoxin was also provided by PCA 4248 at the dose of 1 mg/kg, and lasted for at least 1 hr in the experiments carried out with endotoxin, which caused extravasation with a temporal pattern more protracted than that of PAF and A-IgG. Intradermal extravasation induced by PAF reached a maximum at 30 min after injection, and was also inhibited by PCA 4248. In contrast, PCA 4248 caused a less remarkable, but statistically significant reduction of the intradermal extravasation caused by tumor necrosis factor. Pretreatment of mice with an oral dose of 30 mg/kg PCA 4248, 5 min before challenge with PAF (LD84 = 80 micrograms/kg PAF, i.v.) increased the survival rate from 16% to 68%. These data indicate that compounds containing a 1,4-dihydropyridine structure can antagonize PAF effects on experimental animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacologic activity of bepafant (WEB 2170), a new and selective hetrazepinoic antagonist of platelet activating factor

The hetrazepine WEB 2170 (international nonproprietary name: bepafant), a thieno-triazolodiazepine that is structurally related to the recently described platelet activating factor (PAF) antagonist WEB 2086, is a potent and selective PAF antagonist both in vitro and in vivo. WEB 2170 inhibited PAF-induced human platelet and neutrophil aggregation in vitro (IC50 values: 0.3 and 0.83 microM, respectively) but had little or no inhibitory action against aggregation induced by other agonists. The potency in vitro was comparable to that described recently for WEB 2086 (Casals-Stenzel, J., Muacevic, G. and Weber, K.H.: J. Pharmacol. Exp. Ther. 241: 974-981, 1987). When guinea pigs were given i.v. infusions of PAF at 30 ng x kg-1 x min-1, oral (0.005-0.5 mg/kg) as well as intravenous (0.005-0.05 mg/kg) treatment with WEB 2170 abrogated the intrathoracic accumulation of 111In-labeled platelets, the bronchoconstriction and the hypotension as well as the finally occurring death in a dose-dependent fashion. Oral (0.01-1 mg/kg) and intravenous (0.005-0.1 mg/kg) WEB 2170 shared with the beta 2 agonist fenoterol and the steroid dexamethasone the property of protecting elderly NMRI mice from the lethal effect of PAF. In anesthetized rats, intravenous (0.001-0.1 mg/kg) and oral (0.05-1 mg/kg) WEB 2170 inhibited PAF-induced hypotension in a dose-related manner. Coadministration of WEB 2170 inhibited PAF-induced increase of vascular permeability in rat skin very effectively. The half-time of duration of action in the rat was estimated to be about 5 to 6 h after oral administration and about 1.1 to 2.3 h after intravenous application. In conclusion, the hetrazepine WEB 2170 is a strong and selective PAF antagonist, which is in vitro more or less equipotent to WEB 2086. In contrast, in vivo oral WEB 2170 is--depending on the species and considered parameter--about 5 to 40 times more potent against exogenous PAF-induced alterations than the recently described hetrazepine WEB 2086. Particularly in mice and rats, oral WEB 2170 is by far superior to WEB 2086.     

CV-6209, a highly potent antagonist of platelet activating factor in vitro and in vivo

2-[N-acetyl-N-(2-methoxy-3-octadecylcarbamoyloxypropoxycarbonyl) aminomethyl]-1-ethylpyridinium chloride (CV-6209) inhibited aggregation of rabbit and human platelets induced by platelet activating factor (PAF) with the IC50 values of 7.5 X 10(-8) and 1.7 X 10(-7) M, respectively, and had little effects on the aggregation induced by arachidonic acid, ADP and collagen. The inhibitory effect of CV-6209 on the PAF-induced rabbit platelet aggregation was 104, 9, 8 and 3 times more potent than the PAF antagonists CV-3988, ONO-6240, Ginkgolide B and etizolam, respectively. CV-6209 inhibited [3H]serotonin release from rabbit platelets stimulated with PAF (3 X 10(-8) M) with a similar potency as the inhibition on the platelet aggregation. CV-6209 inhibited PAF (0.3 microgram/kg i.v.)-induced hypotension in rats (ED50, 0.009 mg/kg i.v.) with no effect on the hypotension induced by arachidonic acid, histamine, bradykinin and isoproterenol. CV-6209 (1 mg/kg) inhibited slightly the acetylcholine-induced hypotension. In rats, post-treatment with CV-6209 reversed the PAF (1 microgram/kg i.v.)-induced hypotension rapidly (ED50, 0.0046 mg/kg i.v.); CV-6209 was 74, 20, 185 and over 2100 times more potent than CV-3988, ONO-6240, Ginkgolide B and etizolam, respectively. Thus, the relative potency of the anti-PAF action of PAF analog (CV-6209, CV-3988 and ONO-6240) differed little between the inhibition of PAF-induced platelet aggregation and the reversal of PAF-induced hypotension, but that of nonPAF analogs (Ginkgolide B and etizolam) differed greatly with these assay systems, when standardized with CV-6209.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacological actions of WEB 2086, a new specific antagonist of platelet activating factor

WEB 2086, a thieno-triazolodiazepine, is a potent and specific antagonist of platelet activating factor (PAF) in vitro and in vivo. This compound inhibits PAF-induced human platelet and neutrophil aggregation in vitro (IC50 = 0.17 and 0.36 microM, respectively) but has little or no effect on the action of other platelet aggregating agents. In comparison with kadsurenone, ketotifen or thiazinamium chloride, WEB 2086 was 26 to 200 times more potent in the PAF-induced platelet aggregation. In anesthetized guinea pigs, pretreatment with 0.1 to 2.0 mg/kg p.o. or 0.01 to 0.5 mg/kg i.v. of WEB 2086 inhibits dose-dependently the accumulation and aggregation of 111Indium labeled platelets, bronchoconstriction, systemic hypotension and also the lethal effect due to an i.v. PAF infusion [30 ng/(kg X min)] or intratracheal instillation of PAF (300 micrograms/kg). Under the same experimental conditions in guinea pigs, WEB 2086 given by inhalation achieved a similar anti-PAF activity. In anesthetized rats, the hypotension induced by an i.v. PAF infusion was also reversed (ED50 = 0.052 mg/kg i.v.). The increase in cutaneous vascular permeability due to intradermal PAF (25 ng/site) was inhibited dose-dependently by WEB 2086 (0.025-2 micrograms/site) in rats. Because of its structural relationship to triazolodiazepines, WEB 2086 was examined for anticonvulsant and sedative action. Up to doses of 300 and 800 mg/kg p.o., respectively, no effects were found. In conclusion, WEB 2086 is a potent and specific PAF antagonist with triazolodiazepine structure but without sedative activity.     

Inhibition of the platelet activating factor (PAF)-induced in vivo responses in rats by trans-2,5-(3,4,5-trimethoxyphenyl) tetrahydrofuran (L-652,731), a PAF receptor antagonist

Trans-2,5-bis-(3,4,5-trimethoxyphenyl)tetrahydrofuran (L652, 731), a potent and specific receptor antagonist of platelet activating factor (PAF) (Hwang et al., J. Biol. Chem. 260: 15639-15645, 1985), potently inhibits several PAF-induced in vivo responses in rats. Intravenously and p.o. administered L-652,731 gave a dose-response inhibition of PAF-induced lysosomal hydrolase secretion and extravasation with ED50 values of 1 and 3 mg/kg, respectively. Inhibitions of 87% were achieved with 50 mg/kg p.o. After a single 5-mg/kg p.o. dose, L-652,731 achieved 50 to 60% inhibition of PAF-induced lysosomal hydrolase secretion and extravasation by 0.5 to 1.5 hr with near maximum inhibition lasting through 6 hr. A 20-mg/kg p.o. dose of L-652,731 inhibited PAF-induced leukopenia and neutropenia by 96 and 73%, respectively. The most substantial inhibitions of the extravasation and lysosomal hydrolase secretion induced by PAF or soluble immune complexes were achieved by p.o. L-652,731 (20 mg/kg) with moderate inhibition by dexamethasone and little or no inhibition by antagonists/inhibitors of histamine H1 or H2 or serotonin receptors or cyclooxygenase. Intravenous infusion of a 0.4 mg of L-652,731 bolus inhibited the hypotensive responses from subsequent PAF infusions by a maximum of 72% and with a half-life duration of action of 2.5 hr. Intravenous infusion of L-652,731 results in an immediate 87% reversal of the extreme hypotension induced by a previous endotoxin injection. Thus, with its good p.o. activity, long duration of action and specificity in inhibiting PAF-induced responses in vivo, L-652,731 is a very useful tool in determining the role of PAF in mediating different pathophysiological processes.     

血小板活化因子受体拮抗剂对内毒素血症幼年大鼠肠黏膜上皮细胞间连接蛋白的影响

目的观察血小板活化因子（PAF）对内毒素血症大鼠肠黏膜上皮细胞间连接蛋白β-连环蛋白（β-catenin）的影响，探讨PAF受体拮抗剂对肠上皮屏障完整性的保护作用机制。方法采用腹腔注射脂多糖（LPS）制备内毒素血症大鼠模型。于注射LPS前和注射后30min腹腔注射PAF受体拮抗剂BN52021 5mg／kg作为预防组和治疗组；腹腔注射等量生理盐水作为对照组。分别于注射LPS后1．5、3、6、24、48和72h取各组大鼠回肠，用免疫组化及逆转录-聚合酶链反应（RT—PCR）方法检测肠上皮细胞β-catenin蛋白及mRNA表达。结果对照组β-catenin均匀分布于上皮细胞间细胞膜的表面；内毒素组细胞膜表面β-catenin蛋白明显减少，分布不均。免疫组化和RT—PCR检测均可见内毒素组β-catenin蛋白及mRNA水平明显低于对照组，3～24h内降低非常明显（P均〈0．01）；预防组及治疗组变化趋势同内毒素组，各时间点β-catenin蛋白及mRNA水平均较内毒素组高，但差异无显著性。结论PAF在内毒素血症肠黏膜的机械屏障功能损伤中发挥一定作用，预防和治疗性应用PAF受体拮抗剂BN52021可减轻肠损伤。     

Cardiac functional and structural alterations induced by endotoxin in rats: importance of platelet-activating factor

OBJECTIVE: In this study, we evaluated the time course of the alterations in left ventricular (LV) dimensions, LV wall thickness, and LV systolic function in rats with endotoxemia by using echocardiography as well as myocardial histopathologic assessments. Our second goal was to examine whether pretreatment with a platelet-activating factor (PAF) antagonist would ameliorate the lipopolysaccharide (LPS)-induced cardiovascular collapse during the early phase. DESIGN: A prospective, controlled, in vivo animal laboratory study. SETTING: Research laboratory at a university. SUBJECTS: Male, Wistar rats (8-9 wks old; n = 83). INTERVENTIONS: In pentobarbital-anesthetized rats, the right carotid artery was cannulated to measure the arterial blood pressure and to sample blood. The right jugular vein also was catheterized for the administration of drugs. LPS (2 mg/kg) derived from Klebsiella pneumoniae or physiologic saline was administered in the presence or absence of pretreatment with TCV-309, a specific potent PAF antagonist. Echocardiographic studies were performed with an 8- to 13-MHz transducer. MEASUREMENTS AND MAIN RESULTS: LPS administration immediately induced progressive hypotension. The maximal hypotensive response was observed at 10 mins after LPS infusion with mean arterial pressure decreasing from 119 +/- 2 to 56 +/- 3 mm Hg (p < .001). LV end-diastolic internal dimensions decreased from 6.4 +/- 0.1 to 3.1 +/- 0.1 mm (p < .001) at 30 mins after LPS and remained significantly reduced compared with control rats. LV end-systolic dimensions also decreased dramatically from 3.5 +/- 0.2 to 0.5 +/- 0.1 mm (p < .001) at 30 mins after LPS and remained significantly reduced throughout the experiment. LV fractional shortening increased from 45 +/- 1% to 84 +/- 2% (p < .001) at 30 mins after LPS and remained elevated compared with control rats. LV wall thickness increased strikingly from 15 mins until 2 hrs after LPS infusion. Pathologic studies demonstrated marked congestion of capillaries and mild edema in the LV myocardium. The hematocrit increased after the administration of LPS. LPS markedly increased sympathetic tone as demonstrated by the elevation of plasma concentrations of epinephrine and norepinephrine. There was no elevation of concentrations of nitrite and nitrate. Pretreatment with TCV-309, a specific potent PAF antagonist, reduced LPS-induced hypotension and attenuated LV functional and structural changes. TCV-309 administration reduced the LPS-induced adrenergic activation and hemoconcentration. CONCLUSIONS: The hypotension that occurred during the initial phase of LPS-induced shock was accompanied by LV functional and structural alterations. The marked increase in LV wall thickness can be ascribed to the congestion of capillaries and edema in the LV myocardium. Pretreatment with a PAF antagonist reduced LPS-induced alterations. PAF may play a pivotal role during the initial phase of LPS-induced cardiovascular responses.     

Lisofylline ameliorates intestinal and hepatic injury induced by hemorrhage and resuscitation in rats

OBJECTIVE: We sought to determine whether treatment with lisofylline (LSF) preserves intestinal barrier function in rats subjected to hemorrhagic shock and resuscitation (HS/R). SETTING: Research laboratory at a major university teaching hospital. DESIGN: Rats were bled to a mean arterial pressure of 30 mm Hg and maintained at that pressure for 90 mins. One group (n = 8) was treated with LSF (bolus doses of 15 mg/kg at 45 and 89 min plus infusion at 10 mg x kg(-1) x hr(-1)), whereas another group (n = 8) received only the lactated Ringer's solution (LRS) vehicle. At 90 mins, the animals were resuscitated with shed blood and LRS (55 mL x kg(-1) x hr(-1)). Intestinal mucosal permeability was determined by measuring the mucosal-to-serosal clearance of fluorescein isothiocyanate dextran (molecular weight = 4 kDa) into everted gut sacs. MEASUREMENTS AND MAIN RESULTS: Intestinal and hepatic blood flow (assessed by laser Doppler flowmetry) was greater in LSF-treated rats. Treatment with LSF ameliorated the development of histologic evidence of mucosal damage and hyperpermeability. Rats treated with LSF had lower plasma concentrations of the intracellular hepatic enzyme, aspartate aminotransferase. After 90 mins of resuscitation, concentrations of adenosine triphosphate in intestinal and hepatic tissue were greater in LSF-treated as compared with LRS-treated rats, but concentrations of the endogenous antioxidant, glutathione, in intestinal and hepatic tissue, although lower than in rats not subjected to HS/R, were similar in the two treatment groups. CONCLUSION: Treatment with LSF ameliorated HS/R-induced derangements in intestinal structure and function and hepatic injury, possibly by preserving microvascular perfusion and tissue adenosine triphosphate concentrations.     

银杏苦内酯B对内毒素血症幼鼠肠道的保护作用

目的 胃肠功能障碍与严重感染引起的肠屏障功能破坏密切相关.通过应用血小板活化因子(platelet activating factor,PAF)受体拮抗剂银杏苦内酯B(Ginkgolide B)对幼年大鼠内毒素血症小肠上皮细胞形态学及二胺氧化酶(diamine oxidase,DAO)的影响,探讨PAF在内毒素血症肠损伤中的作用.方法 18日龄Wistar大鼠,随机分为内毒素(lipopolysaccharide,LPS)组和PAF受体拮抗剂组(预防组和治疗组)及对照组(每一时相点n=8),注射LPS后1.5,3,6,24,48,72 h取回肠.LPS组和对照组分别腹腔注射内毒素5 mg/kg及生理盐水1 ml/kg;预防组和治疗组分别于每一时相点注射LPS前、后30 min腹腔注射PAF受体拮抗剂BN52021(Ginkgolide B)5 mg/kg.苏木精-伊红染色及透射电镜作形态学检查.采用分光光度计法分别测定回肠组织及血中DAO含量.根据数据的正态性和方差齐性,选择单因素方差分析ANOVA比较多组间差别,最小显著差异法LSD(least significant difference)-t检验比较两组间差别.所有实验在本院动物实验室、病理实验室、生化实验室及辽宁中医药科大学电镜室进行.结果 1.5,3,6,24 h LPS组可见绒毛水肿,固有层血管充血,间质淋巴管扩张,肠腔炎性渗出;拮抗剂组可见绒毛水肿.电镜下对照组肠微绒毛及细胞间紧密连接未见异常.实验组上皮细胞连接增宽,微绒毛变细、稀疏,部分断裂、脱落;细胞器受损.拮抗剂组改变较实验组减轻.LPS组回肠DAO水平明显低于对照组,6 h从对照组(0.172±0.004)15/mg降至(0.096±0.010)U/mg(F=13.372,P＜0.01);LPS组血浆DAO水平明显高于对照组.预防组及治疗组变化趋势同LPS组.结论 PAF在内毒素血症肠道屏障功能损伤中可能起一定作用,预防和治疗性应用PAF受体拮抗剂Ginkgolide B可减轻肠损伤.血浆和小肠组织中DAO活性同步变化,故测定血浆DAO活性可早期、敏感地反映小肠黏膜功能的破坏.     

Expression of nitric oxide synthase,aquaporin 1 and aquaporin 5 in rat after bleomycin inhalation

OBJECTIVE: Nitric oxide (NO) and aquaporins (AQPs) are believed to play an important role in the pathogenesis of pulmonary inflammation and edema. The aim of this study was to investigate the role of NO synthase (NOS) and AQP in acute lung injury (ALI) lung following bleomycin inhalation in rats. DESIGN AND SETTING: A prospective controlled trial in a university research laboratory. ANIMALS AND INTERVENTIONS: Sprague-Dawley rats were treated by inhalation of 10 U/kg bleomycin hydrochloride in 5 ml of normal saline. Control rats were treated with 5 ml normal saline alone. The animals (6-8 rats per group) were killed on days 4, 7 or 14. MEASUREMENTS AND RESULTS: We analyzed the change in expression of inducible NOS (iNOS), neuronal NOS (nNOS), endothelial NOS (eNOS), aquaporin 1 (AQP1) and aquaporin 5 (AQP5) over time by Western blot. Nitrate and nitrite concentrations were measured in bronchoalveolar lavage fluid (BALF) using a modified Griess reaction. The nitrite and nitrate concentrations in BALF from rats 4 days after bleomycin exposure were greater than those from saline-treated rats. Immunoblotting studies demonstrated increased levels of eNOS in the rat lung at 4, 7 and 14 days and iNOS at 7 and 14 days after bleomycin inhalation. However, nNOS expression was unaltered. Although AQP1 expression was decreased in rats at 4 days, AQP5 expression was increased at 4, 7 and 14 days. CONCLUSIONS: This study demonstrates that NO metabolites increase along with eNOS and iNOS expression during the acute exudative phase in ALI, and that AQP and NOS are regulated independently in bleomycin-induced pulmonary edema.     

Dobutamine restores intestinal mucosal blood flow in a porcine model of intra-abdominal hyperpressure

OBJECTIVE: To assess the effects of dopamine and dobutamine administration on the systemic and mesenteric (macro- and microvascular) circulatory disturbances induced by intra-abdominal hyperpressure. DESIGN: Prospective, randomized study. SETTING: Animal research laboratory in a university hospital. SUBJECTS: Twenty-five pigs of either gender, weighing 30-35 kg. INTERVENTIONS: Animals were anesthetized, and their lungs were mechanically ventilated. Pulmonary artery flotation and carotid artery catheters were inserted for hemodynamic monitoring and blood sampling. A perivascular flow probe was placed around the superior mesenteric artery, and a laser Doppler probe was positioned in the lumen of the ileum to measure arterial and intestinal mucosal blood flows, respectively. CO2 was insufflated into the peritoneal cavity to reach an intra-abdominal pressure of 15 mm Hg, and 60 mins later, animals received dopamine (5 microg/kg/min; n = 10), dobutamine (5 microg/kg/min; n = 10), or saline (n = 5) for 30 mins. MEASUREMENTS AND MAIN RESULTS: Peritoneal CO2 insufflation induced significant increases in heart rate, arterial pressure, and systemic vascular resistance with concomitant decreases in cardiac output and superior mesenteric arterial and intestinal mucosal blood flows. Although dobutamine infusion reversed the decrease in cardiac output, it failed to restore superior mesenteric artery blood flow; however, intestinal mucosal blood flow returned to baseline levels. Dopamine also attenuated the decrease in cardiac output, but it had no beneficial effect on splanchnic hemodynamic variables. CONCLUSIONS: Low-dose infusion of dobutamine, but not dopamine, corrects the intestinal mucosal perfusion impairment induced by moderate increases in intra-abdominal pressure.     

Effects of arginine vasopressin during resuscitation from hemorrhagic hypotension after traumatic brain injury

OBJECTIVE: Two series of experiments were designed to evaluate whether early arginine vasopressin improves acute outcome following resuscitation from traumatic brain injury and severe hemorrhagic hypotension. DESIGN: Prospective randomized, blinded animal study. SETTING: University laboratory. SUBJECTS: Thirty-three swine. INTERVENTIONS: In series 1 (n = 19), after traumatic brain injury with hemorrhage and 12 mins of shock (mean arterial pressure approximately 20 mm Hg), survivors (n = 16) were initially resuscitated with 10 mL/kg crystalloid. After 30 mins, crystalloid and blood with either 0.1 unit x kg(-1) x hr(-1) arginine vasopressin or placebo was titrated to a mean arterial pressure target >or=60 mm Hg. After 90 mins, all received mannitol and the target was cerebral perfusion pressure >or=60 mm Hg. To test cerebrovascular function, 7.5% inhaled CO2 was administered periodically. In series 2 (n = 14), the identical protocol was followed except the shock period was 20 mins and survivors (n = 10) received a bolus of either arginine vasopressin (0.2 units/kg) or placebo during the initial fluid resuscitation. MEASUREMENTS AND MAIN RESULTS: In series 1, by 300 mins after traumatic brain injury with arginine vasopressin (n = 8) vs. placebo (n = 8), the fluid and transfusion requirements were reduced (both p < .01), intracranial pressure was improved (11 +/- 1 vs. 23 +/- 2 mmHg; p < .0001), and the CO2-evoked intracranial pressure elevation was reduced (7 +/- 2 vs. 26 +/- 3 mm Hg, p < .001), suggesting improved compliance. In series 2, with arginine vasopressin vs. placebo, cerebral perfusion pressure was more rapidly corrected (p < .05). With arginine vasopressin, five of five animals survived 300 mins, whereas three of five placebo animals died. The survival time with placebo was 54 +/- 4 mins (p < .05 vs. arginine vasopressin). CONCLUSIONS: Early supplemental arginine vasopressin rapidly corrected cerebral perfusion pressure, improved cerebrovascular compliance, and prevented circulatory collapse during fluid resuscitation of hemorrhagic shock after traumatic brain injury.     

Insulin attenuates endotoxin-induced acute lung injury in conscious rats

OBJECTIVES: To investigate the effects of insulin on the acute lung injury induced by lipopolysaccharide using a conscious rat model. DESIGN: Prospective, randomized, controlled animal study. SETTING: University research laboratory. SUBJECTS: A total of 190 adult male Sprague-Dawley rats weighing 250-300 g. INTERVENTIONS: Endotoxemia was induced by intravenous infusion of lipopolysaccharide. Lipopolysaccharide at various doses (0, 1, 5, 10, 20, and 30 mg/kg, n=10 for each dose) was administered intravenously in 20 mins. Insulin infusion at doses of 0.5, 1, and 5 microU/kg/min was given 5 mins before lipopolysaccharide administration. Plasma glucose was clamped at 90-110 mg/dL by infusion of 10-80% glucose solution. Insulin and glucose infusion (0.01 mL/min) was started 5 mins before lipopolysaccharide and continued for 120 mins. The rats received a total of 60, 120, and 600 microU/kg insulin as well as 0.12, 0.36, and 0.96 g of glucose in respective groups. The animals were then observed for 4 hrs. MEASUREMENTS AND MAIN RESULTS: The extent of acute lung injury was evaluated by lung weight/body weight ratio, lung weight gain, protein concentration in bronchoalveolar lavage, and exhaled nitric oxide. We also measured plasma nitrate/nitrite and methyl guanidine. In addition, histopathologic changes of the lung were examined. Lipopolysaccharide caused systemic hypotension and severe acute lung injury with increases in plasma nitrate/nitrite and methyl guanidine. Pretreatment with insulin infusion at doses of 0.5, 1, and 5 microU/kg/min mitigated or prevented systemic hypotension and the development of acute lung injury, depending on the dose. Insulin also attenuated the lipopolysaccharide-induced increases in nitrate/nitrite and methyl guanidine. CONCLUSIONS: Insulin is effective in reducing or preventing the lipopolysaccharide-induced increases in plasma nitrate/nitrite and methyl guanidine and the occurrence of acute lung injury.     

高压氧对神经病理痛大鼠的NOS系统的影响

目的:观察高压氧对神经病理痛大鼠一氧化氮合酶(nitric oxygen synthase,NOS)系统的影响。方法:40只雄性SD大鼠随机分成五组:即空白对照组(C组);假手术组(S组);坐骨神经慢性缩窄手术组(CCI组);高压氧预处理组(Pre-H组)与高压氧干预组(Post-H组),术后28 d取材观察其脊髓的免疫组化指标,对其NOS各亚型表达进行比较。结果:CCI术后nNOS,iNOS表达明显增加,Pre-H组和Post-H组的nNOS及iNOS含量较CCI组明显降低。eNOS含量在整个过程中变化不大。结论:高压氧可能通过抑制NOS系统表达产生对CCI大鼠疼痛的抑制作用。     

7-硝基吲唑在烟雾吸入性肺损伤中的作用

目的 探讨神经型一氧化氮合酶（nNOS）抑制剂7-硝基吲唑（7-NI）在烟雾吸入性肺损伤中的作用。方法 40只SD雄性大鼠被随机分为正常对照组（n=8）、烟雾吸入性肺损伤模型组（n=16）和7-NI治疗组（n=16），建立烟雾吸入性肺损伤模型。7-NI治疗组在致伤后立即腹腔注射7-NI 20mg／kg（溶于2ml花生油中）；正常对照组及模型组腹腔注射2ml花生油。分别于伤后2、6、12和24h时间点监测动脉血气分析；并分批处死大鼠，取肺组织测肺含水量，制备肺组织匀浆检测超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、各型一氧化氮合酶（NOS）活性及肿瘤坏死因子-α（TNF—α）和一氧化氮（NO）含量。光镜下观察肺组织病理学变化。结果 与模型组比较，7～NI治疗组各时间点动脉血氧分压均显著升高（P均〈0．05），肺组织含水量显著降低（P〈0．05），肺组织中SOD及CAT活性均明显升高（P均〈0．05），nNOS活性及NO含量均明显降低（P均〈0．05）。治疗组2h和6h肺组织中TNF—α含量均较模型组降低（P均〈0．05）。光镜下7-NI治疗组较模型组损伤程度减轻，炎性细胞浸润减少，肺间质内未见点状出血。结论 7-NI对烟雾吸人性肺损伤有较好的保护作用，可提高动脉血氧分压，减轻肺水肿程度，增加组织抗氧化能力，并减轻组织炎性细胞浸润。     

Sch 37370: a potent, orally active, dual antagonist of platelet-activating factor and histamine

Platelet-activating factor (PAF) and histamine are potent bronchospastic agents and possess additional properties such as induction of vasopermeability and activation of inflammatory cells that are consistent with their ability to mediate allergic and inflammatory responses. From a structural series with anticipated antihistamine activity, Sch 37370 (1-acetyl-4(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2- b]pyridine-11-ylidine)piperidine) has been identified as a dual antagonist of PAF and histamine in vitro and in vivo and has been compared with several selective antagonists of PAF and histamine. Sch 37370 selectively inhibits PAF-induced aggregation of human platelets (IC50 = 0.6 microM) and also competes with PAF binding to specific sites in membrane preparations from human lungs (IC50 = 1.2 microM). Sch 37370 blocks the binding of [3H]pyrilamine to histamine-H1 receptors in rat brain membranes. Administered i.v. to guinea pigs, Sch 37370 is an equipotent antagonist of PAF and histamine-induced bronchospasm (ED50 = 0.6-0.7 mg/kg). Orally in guinea pigs, Sch 37370 is somewhat more effective against bronchospasms to histamine (ED50 = 2.4 mg/kg) than against PAF (ED50 = 4.1-6.0 mg/kg) or serotonin (ED50 = 9.6 mg/kg). Sch 37370 only weakly antagonizes methacholine-induced bronchospasm (ED50 = 51 mg/kg) and is completely inactive at 50 mg/kg against leukotriene C4 or substance P. Sch 37370 blocks hypotension in rats and a cutaneous reaction in monkeys induced by either PAF or histamine, as well as PAF-induced lethality in mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Adrenomedullin reduces Staphylococcus aureus alpha-toxin-induced rat ileum microcirculatory damage

OBJECTIVE: Increased microvascular permeability and perfusion mismatch are hallmarks of sepsis or septic shock. The intestinal mucosa is very sensitive to tissue hypoxia. Intestinal mucosa dysfunction may allow translocation of bacteria and their products, thereby perpetuating sepsis and inflammation. Staphylococcus aureus alpha-toxin is a major pathogenicity determinant of this bacterium, provoking cardiovascular collapse. Current evidence suggests that the endogenous peptide adrenomedullin stabilizes circulatory homeostasis in systemic inflammatory response. Using alpha-toxin as a well-defined strong initiator of an inflammatory reaction, we tested the hypothesis that exogenously applied adrenomedullin stabilizes gut microcirculation. DESIGN: Prospective, experimental study. SETTING: Research laboratory at a university hospital. SUBJECTS: Isolated, perfused ileum from male Sprague-Dawley rats and human umbilical vein endothelial cells. INTERVENTIONS: Administration of S. aureus alpha-toxin before or after infusion of adrenomedullin. MEASUREMENTS AND MAIN RESULTS: Injection of a bolus of 1 microg of alpha-toxin in the superior mesenteric artery in a constant-flow, blood-perfused preparation of rat ileum increased perfusion pressure and relative hemoglobin concentration and decreased mucosal hemoglobin oxygen saturation. Continuous infusion of adrenomedullin (0.1 micromol/L) significantly reduced these alpha-toxin-related effects. Severe microvascular hyperpermeability observed in alpha-toxin-exposed ileum was abolished by adrenomedullin pretreatment. In addition, adrenomedullin blocked alpha-toxin-induced endothelial myosin light chain phosphorylation, endothelial cell contraction, and subsequent loss of endothelial barrier function in vitro. Treatment of alpha-toxin (infusion of 0.05 microg/mL)-exposed ileum with adrenomedullin (0.1 micromol/L) started 10 mins after onset of toxin application also significantly reduced superior mesenteric artery pressure and permeability increase. CONCLUSIONS: In summary, these data suggest that exogenous adrenomedullin protects ileum by reducing alpha-toxin-induced microcirculatory disturbances and by stabilizing endothelial barrier function.