Dexamethasone attenuates acute macromolecular efflux increase evoked by smokeless tobacco extract.

The purpose of this study was to determine whether dexamethasone attenuates the acute increase in macromolecular efflux from the oral mucosa elicited by an aqueous extract of smokeless tobacco (STE) in vivo, and, if so, whether this response is specific. Using intravital microscopy, we found that 20-min suffusion of STE elicited significant, concentration-related leaky site formation and an increase in clearance of fluorescein isothiocyanate-labeled dextran (FITC-dextran; mol mass 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This response was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethasone also attenuated the bradykinin-induced leaky site formation and the increase in clearance of FITC-dextran from the cheek pouch. However, it had no significant effects on adenosine-induced responses. Dexamethasone had no significant effects on baseline arteriolar diameter and on bradykinin-induced vasodilation in the cheek pouch. Collectively, these data indicate that dexamethasone attenuates, in a specific fashion, the acute increase in macromolecular efflux from the in situ oral mucosa evoked by short-term suffusion of STE. We suggest that corticosteroids mitigate acute oral mucosa inflammation elicited by smokeless tobacco.     

Improved functional vasodilation in obese Zucker rats following exercise training

Obese individuals exhibit impaired functional vasodilation and exercise performance. We have demonstrated in obese Zucker rats (OZ), a model of morbid obesity, that insulin resistance impairs functional vasodilation via an increased thromboxane receptor (TP)-mediated vasoconstriction. Chronic treadmill exercise training improves functional vasodilation in the spinotrapezius muscle of the OZ, but the mechanisms responsible for the improvement in functional vasodilation are not clear. Based on evidence that exercise training improves insulin resistance, we hypothesized that, in the OZ, exercise training increases functional vasodilation and exercise capability due to decreases TP-mediated vasoconstriction associated with improved insulin sensitivity. Six-week-old lean Zucker rats (LZ) and OZ were exercised on a treadmill (24 m/min, 30 min/day, 5 days/wk) for 6 wk. An oral glucose tolerance test was performed at the end of the training period. We measured functional vasodilation in both exercise trained (spinotrapezius) and nonexercise trained (cremaster) muscles to determine whether the improved functional vasodilation following exercise training in OZ is due to a systemic improved insulin resistance. Compared with LZ, the sedentary OZ exhibited impairments in glucose tolerance and functional vasodilation in both muscles. The TP antagonist SQ-29548 improved the vasodilator responses in the sedentary OZ with no effect in the LZ. Exercising training of the LZ increased the functional vasodilation in spinotrapezius muscle, with no effect in the cremaster muscle. Exercising training of the OZ improved glucose tolerance, along with increased functional vasodilation, in both the spinotrapezius and cremaster muscles. SQ-29548 treatment had no effect on the vasodilator responses in either cremaster or spinotrapezius muscles of the exercise-trained OZ. These results suggest that, in the OZ, there is a global effect of exercising training to improve insulin resistance and increase functional vasodilation via a decreased TP-mediated vasoconstriction.     

Time course of flow-induced vasodilation in skeletal muscle: contributions of dilator and constrictor mechanisms

The purpose of this study was to determine the time course of flow-induced vasodilation in soleus and gastrocnemius muscle arterioles and the mechanisms that underlie vasodilatory responses to an increase in intraluminal flow. Vasodilation was assessed during 20 min of continuous exposure to intraluminal flow. Both soleus and gastrocnemius muscle arterioles dilated in response to flow, although the magnitude of vasodilation was greater in arterioles from the gastrocnemius muscle. Neither blockade of nitric oxide synthase with N(G)-nitro-L-arginine methyl ester (L-NAME) nor blockade of cyclooxygenase with indomethacin inhibited the initial vasodilation (0-2 min) in arterioles from either muscle. In contrast, vasodilation to sustained exposure to flow (2-20 min) was eliminated by treatment with L-NAME in arterioles from both muscles. Both depolarization with 40 mM KCl and blockade of Ca(2+)-activated K(+) channels inhibited the initial flow-induced dilation, and the inhibition was greater in gastrocnemius muscle arterioles than soleus muscle arterioles. In the presence of L-NAME, prolonged exposure to flow resulted in constriction in soleus and gastrocnemius muscle arterioles. This constriction was abolished by endothelin receptor blockade. These results indicate that the time course and magnitude of flow-induced vasodilation differs between arterioles from soleus and gastrocnemius muscles. The immediate response to increased flow is greater in gastrocnemius muscle arterioles and involves activation of K(+) channels. In arterioles from both soleus and gastrocnemius muscles, vasodilation to sustained flow exposure occurs primarily through production of nitric oxide. In the absence of nitric oxide, sustained exposure to flow results in pronounced constriction that is mediated by endothelin.     

Hog barn dust extract increases macromolecular efflux from the hamster cheek pouch.

The purpose of this study was to determine whether short-term exposure to an aqueous extract of hog barn dust increases macromolecular efflux from the intact hamster cheek pouch and, if so, to begin to determine the mechanism(s) underlying this response. By using intravital microscopy, we found that suffusion of hog barn dust extract onto the intact hamster cheek pouch for 60 min elicited a significant, concentration-dependent leaky site formation and increase in clearance of FITC-labeled dextran (molecular mass, 70 kDa). This response was significantly attenuated by suffusion of catalase (60 U/ml), but not by heat-inactivated catalase, and by pretreatment with dexamethasone (10 mg/kg iv) (P < 0.05). Catalase had no significant effects on adenosine-induced increase in macromolecular efflux from the cheek pouch. Suffusion of hog barn dust extract had no significant effects on arteriolar diameter in the cheek pouch. Taken together, these data indicate that hog barn dust extract increases macromolecular efflux from the in situ hamster cheek pouch, in part, through local elaboration of reactive oxygen species that are inactivated by catalase. This response is specific and attenuated by corticosteroids. We suggest that plasma exudation plays an important role in the genesis of upper airway dysfunction evoked by short-term exposure to hog barn dust.     

Inhaled nebulized nitrite is a hypoxia-sensitive NO-dependent selective pulmonary vasodilator

The blood anion nitrite contributes to hypoxic vasodilation through a heme-based, nitric oxide (NO)-generating reaction with deoxyhemoglobin and potentially other heme proteins. We hypothesized that this biochemical reaction could be harnessed for the treatment of neonatal pulmonary hypertension, an NO-deficient state characterized by pulmonary vasoconstriction, right-to-left shunt pathophysiology and systemic hypoxemia. To test this, we delivered inhaled sodium nitrite by aerosol to newborn lambs with hypoxic and normoxic pulmonary hypertension. Inhaled nitrite elicited a rapid and sustained reduction ( approximately 65%) in hypoxia-induced pulmonary hypertension, with a magnitude approaching that of the effects of 20 p.p.m. NO gas inhalation. This reduction was associated with the immediate appearance of NO in expiratory gas. Pulmonary vasodilation elicited by aerosolized nitrite was deoxyhemoglobin- and pH-dependent and was associated with increased blood levels of iron-nitrosyl-hemoglobin. Notably, from a therapeutic standpoint, short-term delivery of nitrite dissolved in saline through nebulization produced selective, sustained pulmonary vasodilation with no clinically significant increase in blood methemoglobin levels. These data support the concept that nitrite is a vasodilator acting through conversion to NO, a process coupled to hemoglobin deoxygenation and protonation, and evince a new, simple and inexpensive potential therapy for neonatal pulmonary hypertension.     

Interactions of VIP with rigid phospholipid bilayers: implications for vasoreactivity

The purpose of this study was to determine whether vasoactive intestinal peptide (VIP), a pleiotropic amphipathic peptide, interacts with rigid liposomes composed of gel phase phospholipids. We found that incubation of VIP with small unilamellar gel phase liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and egg phosphatidylglycerol (ePG) for 2h at room temperature had no significant effects on VIP secondary structure. Moreover, suffusion of VIP (0.01, 0.1 and 1.0nmol) incubated in saline or with DPPC/ePG liposomes (size, 30 and 100nm) for 2h at room temperature or 4 degrees C onto the intact hamster cheek pouch microcirculation elicited a similar concentration-dependent vasodilation except for 0.01nmol VIP (P<0.05). By contrast, incubation of VIP with gel phase liposomes overnight at 4 degrees C significantly potentiated vasodilation evoked by all three concentrations of the peptide in comparison to aqueous VIP (P<0.05). VIP-induced vasodilation was liposome size-independent. The ratio of VIP to phospholipids in DPPC/ePG liposomes was concentration-independent. Collectively, these data indicate that short-term interactions of VIP with rigid phospholipid bilayers are limited resulting in only modest effects on VIP vasoreactivity in vivo.     

Downhill treadmill running trains the rat spinotrapezius muscle.

There are currently no models of exercise that recruit and train muscles, such as the rat spinotrapezius, that are suitable for transmission intravital microscopic investigation of the microcirculation. Recent experimental evidence supports the concept that running downhill on a motorized treadmill recruits the spinotrapezius muscle of the rat. Based on these results, we tested the hypothesis that 6 wk of downhill running (-14 degrees grade) for 1 h/day, 5 days/wk, at a speed of up to 35 m/min, would 1) increase whole body peak oxygen uptake (Vo(2 peak)), 2) increase spinotrapezius citrate synthase activity, and 3) reduce the fatigability of the spinotrapezius during electrically induced 1-Hz submaximal tetanic contractions. Trained rats (n = 6) elicited a 24% higher Vo(2 peak) (in ml.min(-1).kg(-1): sedentary 58.5 +/- 2.0, trained 72.7 +/- 2.0; P < 0.001) and a 41% greater spinotrapezius citrate synthase activity (in mumol.min(-1).g(-1): sedentary 14.1 +/- 0.7, trained 19.9 +/- 0.9; P < 0.001) compared with sedentary controls (n = 6). In addition, at the end of 15 min of electrical stimulation, trained rats sustained a greater percentage of the initial tension than their sedentary counterparts (control 34.3 +/- 3.1%, trained 59.0 +/- 7.2%; P < 0.05). These results demonstrate that downhill running is successful in promoting training adaptations in the spinotrapezius muscle, including increased oxidative capacity and resistance to fatigue. Since the spinotrapezius muscle is commonly used in studies using intravital microscopy to examine microcirculatory function at rest and during contractions, our results suggest that downhill running is an effective training paradigm that can be used to investigate the mechanisms for improved microcirculatory function following exercise training in health and disease.     

Nitric oxide modulates endotoxin-induced platelet-endothelial cell adhesion in intestinal venules

Although platelets have been implicated in the pathogenesis of vascular diseases, little is known about factors that regulate interactions between platelets and the vessel wall under physiological conditions. The objectives of this study were to 1) define the contribution of nitric oxide (NO) to endotoxin (lipopolysaccharide, LPS)-induced platelet-endothelial cell (P/E) adhesion in murine intestinal venules and 2) determine whether the antiadhesive action of NO is mediated by soluble guanylate cyclase (sGC). Adhesive interactions between platelets and endothelial cells were monitored by intravital microscopy. LPS administration into control wild-type mice (WT) resulted in a >15-fold increase in P/E adhesion. Similar responses were observed using endothelial NO synthase (eNOS)-deficient platelets. However, treatment with the NO donor diethylenetriamine-nitric oxide (DETA-NO) attenuated the P/E adhesion response to LPS, whereas the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester or eNOS deficiency resulted in an exacerbation. P/E adhesion response did not differ between LPS-treated WT and inducible NOS-deficient mice. Inhibition of sGC abolished the attenuating effects of DETA-NO, whereas the sGC activator 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) reduced LPS-induced P/E adhesion. These findings indicate that 1) eNOS-derived NO attenuates endotoxin-induced P/E adhesion and 2) sGC is responsible for the antiadhesive action of NO.     

PGH(2)-TxA(2)-receptor blockade restores vasoreactivity in a new rodent model of genetic hypertension.

The purpose of this study was to determine whether activation of prostaglandin H(2)-thromboxane A(2) (PGH(2)-TxA(2)) receptors impedes vasodilation in the in situ peripheral microcirculation of spontaneously hypertensive hamsters, a new rodent model of high-renin genetic hypertension. Using intravital microscopy, we found that vasodilation elicited by suffusion of acetylcholine and vasoactive intestinal peptide (VIP), two neurotransmitters localized in perivascular nerves in the peripheral circulation, on the in situ cheek pouch was significantly attenuated in spontaneously hypertensive hamsters relative to age- and genetically matched normotensive hamsters (P < 0.05). However, nitroglycerin-induced vasodilation was similar in both groups. Pretreatment with SQ-29548, a selective and potent PGH(2)-TxA(2)-receptor antagonist, restored acetylcholine- and VIP-induced vasodilation in spontaneously hypertensive hamsters. SQ-29548 had no significant effects on resting arteriolar diameter and on nitroglycerin-induced vasodilation in both groups. SQ-29548 slightly but significantly potentiated VIP- but not acetylcholine-induced vasodilation in normotensive hamsters. Collectively, these data indicate that activation of PGH(2)-TxA(2) receptors impedes agonist-induced vasodilation in the in situ cheek pouch of spontaneously hypertensive hamsters. We suggest that this model is suitable for studying the role of prostanoids in mediating vasomotor dysfunction observed in genetic hypertension.     

Different bacterial lipopolysaccharides as toxicants and stressors in the shrimp Palaemon elegans

This study compares the in vivo haemocytic response of shrimp, Palaemon elegans (Rathke) to different types of LPS injection. In particular it investigates to what degree and speed the haemocytopenia varies between LPSs from different sources. It further compares the tolerated doses of different LPSs in these animals and finds substantial differences in the various toxicity types. The work then relates this to blood glucose levels and stress-linked variations in glycaemic status. The order of LPS decreasing toxicity determined by LD50 at 96 h was: Salmonella enteritidis, Serratia marcescens, Pseudomonas aeruginosa 10, Escherichia coli K-235 and E. coli 0111:B4. Eyestalkless animals were more sensitive to LPS. The effects of injected LPS on circulating total blood cell count (THC) was tested. The results show that LPS caused a decrease in THC 8 h after injection and then the THC returned to the initial level and this effect depended on the LPS tested. E. coli K-235 was the most effective in causing haemocytopenia followed by E. coli 0111:B4, S. enteritidis, S. marcescens, and P. aeruginosa 10. Moreover, LPS-induced increases in the blood glucose level and the time and dose related curves of response obtained depended on the type of LPS tested. E. coli K-235 LPS was again the most effective in elevating blood glucose followed by E. coli 0111:B4, S. marcescens, S. enteritidis and then P. aeruginosa 10. No significant hyperglycaemia was induced in eyestalkless animals. An inverse order relationship between toxicity (LD50) and stress responses (hyperglycaemia and THC decrease) may suggest a defensive and adaptive role of the latter in occasional septicaemia.     

Lipopolysaccharide reduces intercellular coupling in vitro and arteriolar conducted response in vivo

Our recent in vitro study (Lidington et al. J Cell Physiol 185: 117-125, 2000) suggested that lipopolysaccharide (LPS) reduces communication along blood vessels. The present investigation extended this study to determine whether any effect of LPS and/or inflammatory cytokines [tumor necrosis factor-alpha, interleukin (IL)-1beta, and IL-6] on endothelial cell coupling in vitro could also be demonstrated for an arteriolar conducted response in vivo. Using an electrophysiological approach in monolayers of microvascular endothelial cells, we found that LPS (10 microg/ml) but not these cytokines reduced intercellular conductance (c(i)) (an index of cell communication) and that LPS together with these cytokines did not further reduce c(i). Also, c(i) was restored after LPS washout, and the LPS-induced reduction was prevented by protein tyrosine kinase (PTK) inhibitors (1.5 microM Tyr A9 and 10 nM PP-2). In our in vivo experiments in arterioles of the mouse cremaster muscle, local electrical stimulation evoked vasoconstriction that conducted along arterioles. LPS in the muscle superfusate did not alter local vasoconstriction but reduced the conducted response. Washout of LPS restored the conducted response, whereas PTK inhibitors prevented the effect of LPS. On the basis of a newly developed mathematical model, the LPS-induced reduction in conducted response was predicted to reduce the arteriolar ability to increase resistance to blood flow. We conclude that LPS can reduce communication in in vitro and in vivo systems comparably in a reversible and tyrosine kinase-dependent manner. Based on literature and present results, we suggest that LPS may compromise microvascular hemodynamics at both the arteriolar responsiveness and the conduction levels.     

Exercise training enhances adrenergic constriction and dilation in the rat spinotrapezius muscle

Treadmill training increases functionalvasodilation in the rat spinotrapezius muscle, although there is noacute increase in blood flow and no increase in oxidative capacity. Toassess concurrent changes in vascular reactivity, we measured arterial diameters in the spinotrapezius muscle of sedentary (Sed) and treadmill-trained (Tr; 9-10 wk; terminal intensity 30 m/min,1.5° incline, for 90 min) rats during iontophoretic application of norepinephrine, epinephrine (Epi), andH⁺ (HCl) and during superfusionwith adenosine. Terminal-feed arteries and first-order arterioles in Trrats constricted more than those in Sed rats at the higher currentdoses of norepinephrine and Epi. In contrast, at low-current doses ofEpi, first- and second-order arterioles dilated in Tr but not in Sedrats. The vascular responses to HCl were highly variable, butsecond-order arterioles of Tr rats constricted more than those of Sedrats at intermediate-current doses. There were no significantdifferences between Sed and Tr rats in the vascular responses toadenosine. Both adrenergic vasodilation and vasoconstriction wereenhanced in the spinotrapezius muscle of Tr rats, and enhancedadrenergic vasodilation may contribute to increased functionalvasodilation. These observations further demonstrate vascularadaptations in "nontrained" skeletal muscle tissues.

     

Downhill running: a model of exercise hyperemia in the rat spinotrapezius muscle.

To utilize the rat spinotrapezius muscle as a model to investigate the microcirculatory consequences of exercise training, it is necessary to design an exercise protocol that recruits this muscle. There is evidence that the spinotrapezius is derecruited during standard treadmill exercise protocols performed on the uphill treadmill (i.e., 6 degrees incline). This investigation tested the hypothesis that downhill running would effectively recruit the spinotrapezius muscle as assessed by the presence of an exercise hyperemia response. We used radioactive 15-microm microspheres to determine blood flows in the spinotrapezius and selected hindlimb muscles of female Sprague-Dawley rats at rest and during downhill (i.e., -14 degrees incline; 331 +/- 5 g body wt, n = 7) and level (i.e., 0 degrees incline; 320 +/- 11 g body wt, n = 5) running at 30 m/min. Both level and downhill exercise increased blood flow to all hindlimb muscles (P < 0.01). However, in marked contrast to the absence of a hyperemic response to level running, blood flow to the spinotrapezius muscle increased from 26 +/- 6 ml.min(-1).100 g(-1) at rest to 69 +/- 8 ml.min(-1).100 g(-1) during downhill running (P < 0.01). These findings indicate that downhill running represents an exercise paradigm that recruits the spinotrapezius muscle and thereby constitutes a tenable physiological model for investigating the adaptations induced by exercise training (i.e., the mechanisms of altered microcirculatory control by transmission light microscopy).     

Disruption of the rat mesenteric arterial bed endothelial function by air perfusion

The impact of air perfusion on the endothelial function of the rat mesenteric arterial bed (MAB; perfused with Krebs' bicarbonate plus indomethacin) was compared to that of the NO synthase inhibitor, N^ω-nitro-L-arginine methyl ester (L-NAME). Air shifted the dose-response curve for the alpha-adrenoceptor agonist, norepinephrine (NE) to the left (ED_50%: 2.9 ± 0.7 to 0.9 ± 0.7 μg, P < 0.05); maximal vasoconstriction did not change. L-NAME produced a similar increase in midrange sensitivity (ED_50% 1.4 ± 0.7 μg, P < 0.05) and a 20% increase in maximum (152 ± 6 to 183 ± 7 mmHg, P < 0.05). Electromechanical stimulation with potassium chloride (KCL) was not modified by reserpine. Neither air nor L-NAME modified midrange sensitivity to KCL. L-NAME produced a 17% increase in maximum (91 ± 4 to 107 ± 5 mmHg, P < 0.05); reserpine abolished the latter effect. Air and L-NAME diminished endothelium-dependent vasodilation elicited by carbachol. Air did not modify endothelium-dependent vasodilation elicited by sodium nitroprusside; this response was potentiated by L-NAME. In summary, air and L-NAME produced similar effects on receptor-dependent activation of the endothelial L-arginine nitric oxide (NO) pathway. Potentiation by L-NAME of the maximal electromechanical response suggests the existence of a tone-dependent NO system. Abolition of the latter response by reserpine suggests that this system is of sympathetic origin.     

两种败血症休克模型大鼠心肌细胞一氧化氮合酶活性的改变

目的：观察两种败血症休克模型大鼠的血流动力学及心肌细胞一氧化氮合酶活性变化的异同,探讨一氧化氮合酶参与败血症休克性心肌抑制的机制。方法：采用注射脂多糖（LPS）诱导及盲肠结扎穿孔（CLP）致腹膜炎诱导败血症休克模型,测定血流动力学指标以及心肌细胞胞浆一氧化氮合酶（NOS）活性。结果：①CLP模型大鼠的血流动力学指标随时间呈先上升后下降的趋势,LPS模型直接表现为类似于CLP模型晚期的动力学状态。在使用NOS抑制剂N-硝基-L精氨酸甲酯（L-NAME）后,CLP模型晚期及LPS模型的心室动力学指标均有明显改善。②CLP模型大鼠心肌细胞胞浆NOS活性在败血症中期达到最大。与假手术组相比,LPS模型、CLP模型晚期心肌细胞胞浆NOS活性均有明显增加,但是LPS模型与CLP模型晚期两组之间无明显差异。③使用L-NAME后,CLP晚期组与LPS组亚硝基及硝基化合物生成量均明显降低（P〈0.01）。其中,LPS组与CLP晚期组相比,前者固定表达型NOS生成亚硝基及硝基化合物生成量明显高于后者（P〈0．01）。结论：在LPS与CLP诱导的败血症休克模型中,心肌NOS是引起心室动力学变化的主要因素;在两种模型,心肌NOS亚型的表达不同,在LPS模型中主要为iNOS,而在CLP模型中则可能是cNOS和iNOS共同发挥作用。     

Helospectin I and II evoke vasodilation in the intact peripheral microcirculation

Helospectin I and II, two closely related mammalian neuropeptides of the secretin/glucagons/vasoactive intestinal peptide (VIP) superfamily of peptides, are co-localized with VIP in nerve fibers surrounding vascular smooth muscle. However, the role if any, VIP receptors play in transducing the vasorelaxant effects of helospectin I and II in the intact peripheral microcirculation is uncertain. The purpose of this study was to determine whether helospectin I and II elicit vasodilation in the intact peripheral microcirculation and, if so, whether this response is mediated, in part, by VIP or pituitary adenylate cyclase activating peptide (PACAP) receptor engagement, and through local elaboration of cyclooxygenase products of arachidonic acid metabolism. Using intravital microscopy, we found that suffusion of helospectin I and II (each, 1.0 nmol) evoked potent vasodilation and of similar magnitude in the intact hamster cheek pouch microcirculation (P < 0.05). Suffusion of 0.1 nmol helospectin I and II had no significant effects on arteriolar diameter. Pretreatment with VIP(10-28), a VPAC1/VPAC2 receptor antagonist, or PACAP(6-38), a PAC1/VPAC2 receptor antagonist, had no significant effects on helospectin I- and II-induced responses. In addition, pretreatment with indomethacin had no significant effects on helospectin I- and II-induced vasodilation. Collectively, these data indicate that helospectin I and II evoke potent vasodilation in the intact peripheral microcirculation that is not transduced by VIP or PACAP receptors nor through cyclooxygenase products of arachidonic acid metabolism.     

Endotoxaemia in rats: role of NO, PAF and TXA2 in pulmonary neutrophil sequestration and hyperlactataemia.

OBJECTIVE AND DESIGN: The involvement of PAF, TXA2 and NO in LPS-induced pulmonary neutrophil sequestration an hyperlactataemia was studied in conscious rats. As pharmacological tools WEB 2170 (PAF receptor antagonist, 20 mg/kg), camongarel (inhibitor of TXA2 synthase, 30 mg/kg), N(G)-nitro L-arginine methyl ester (L-NAME -- non-selective nitric oxide synthase inhibitor, 30 mg/kg) were used. METHODS: Plasma lactate and NO2-/NO3- levels as well as myeloperoxidase (MPO) activity in lung tissue were measured one and five hours after administration of LPS (4 mg/kg(-1)). RESULTS: LPS induced a twofold increase in plasma lactate levels and nearly 10-fold increase in plasma NO2-/NO3- levels five but not one hour after LPS administration. However, LPS-induced increase in pulmonary MPO activity was seen at both time intervals. Neither WEB 2170 nor camonagrel changed one or five hours responses to LPS (lactate, NO2-/NO3-, MPO). L-NAME potentiated LPS-induced rise in MPO activity in the lung and this potentiation was not affected by WEB 2170 or camonagrel. L-NAME supressed plasma NO2-/NO3- response and substantially potentiated plasma lactate response to LPS and both effects were partially reversed by WEB 2170 or camonagrel. CONCLUSIONS: In summary, we demonstrated that PAF and TXA 2 play a role in overproduction of lactate during endotoxaemia in NO-deficient rats. However, these lipids do not mediate endotoxin-induced sequestration of neutrophils in the lung.     

Role of endogenous nitric oxide in endotoxin-induced alteration of hypoxic pulmonary vasoconstriction in mice

Pulmonary vasoconstriction in response to alveolar hypoxia (HPV) is frequently impaired in patients with sepsis or acute respiratory distress syndrome or in animal models of endotoxemia. Pulmonary vasodilation due to overproduction of nitric oxide (NO) by NO synthase 2 (NOS2) may be responsible for this impaired HPV after administration of endotoxin (LPS). We investigated the effects of acute nonspecific (N(G)-nitro-L-arginine methyl ester, L-NAME) and NOS2-specific [L-N6-(1-iminoethyl)lysine, L-NIL] NOS inhibition and congenital deficiency of NOS2 on impaired HPV during endotoxemia. The pulmonary vasoconstrictor response and pulmonary vascular pressure-flow (P-Q) relationship during normoxia and hypoxia were studied in isolated, perfused, and ventilated lungs from LPS-pretreated and untreated wild-type and NOS2-deficient mice with and without L-NAME or L-NIL added to the perfusate. Compared with lungs from untreated mice, lungs from LPS-challenged wild-type mice constricted less in response to hypoxia (69 +/- 17 vs. 3 +/- 7%, respectively, P < 0.001). Perfusion with L-NAME or L-NIL restored this blunted HPV response only in part. In contrast, LPS administration did not impair the vasoconstrictor response to hypoxia in NOS2-deficient mice. Analysis of the pulmonary vascular P-Q relationship suggested that the HPV response may consist of different components that are specifically NOS isoform modulated in untreated and LPS-treated mice. These results demonstrate in a murine model of endotoxemia that NOS2-derived NO production is critical for LPS-mediated development of impaired HPV. Furthermore, impaired HPV during endotoxemia may be at least in part mediated by mechanisms other than simply pulmonary vasodilation by NOS2-derived NO overproduction.     

Endothelium-dependent vascular relaxation induced by Globularia alypum extract is mediated by EDHF in perfused rat mesenteric arterial bed

The vasodilatory effect of Globularia alypum L. (GA) extract was evaluated in rat mesenteric arterial bed pre-contracted by continuous infusion of phenylephrine (2-4 ng/mL). Bolus injections of GA elicited dose-response vasodilation, which was abolished after endothelium removal. Addition of a nitric oxide synthase inhibitor, N(G)-nitro-l-arginine methyl ester (100 μmol/L), alone or in the presence of a cyclooxygenase inhibitor, indomethacin (10 μmol/L), did not significantly affect the vasodilation of the mesenteric arterial bed in response to GA extract. These results suggest that GA-induced vasodilation is endothelium dependent but nitric oxide and prostacyclin independent. In the presence of high K(+) (60 mmol/L), the GA vasodilatory effect was completely abolished, suggesting that the vasodilation effect is mediated by hyperpolarization of the vascular cells. Also, pre-treatment with atropine (a muscarinic receptors antagonist) antagonized the GA-induced vasodilation, suggesting that the vasodilatory effect is mainly mediated by the endothelium-derived hyperpolarizing factor through activation of endothelial muscarinic receptors.     

Role of centrally administered melatonin and inhibitors of COX and NOS in LPS-induced hyperthermia and adipsia.

In the present study we have examined the effect of centrally administered non-steroidal anti-inflammatory drugs (NSAIDS), nitric oxide synthase (NOS) inhibitor and melatonin on lipopolysaccharide (LPS)-induced hyperthermia and its anti-dipsogenic effect. Intracerebroventricular (i.c.v.) administration of LPS (100-200 ng/rat) induces a dose dependent elevation in body temperature and decreases water consumption in 24 h water deprived rats. Coadministration of NSAIDS (indomethacin and nimesulide: 10 nM/rat each) with LPS (100 ng) reversed, whereas NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME: 10-20 microg/rat) enhanced LPS-induced hyperthermia. In contrast L-NAME reversed the LPS-induced anti-dipsogenic effect in a dose dependent manner, whereas NSAIDS showed no change in the effect of LPS. Further, centrally administered prostaglandin E2 (PGE2, 0.5-1 microg/rat) produced hyperthermia without affecting the drinking behavior, suggesting that two independent mechanisms operate in LPS-induced hyperthermia and in the anti-dipsogenic effect. The pineal hormone melatonin is known to inhibit cellular damage caused by LPS, produced dose dependent (5-10 nM i.c.v.) inhibition of LPS-induced hyperthermia and adipsia, but failed to reverse the PGE2-induced hyperthermia, shows reversal of LPS-induced hyperthermia by melatonin is due to inhibition of prostaglandin synthesis rather than antagonism of prostaglandin action. The overall study reveals that inhibition of both NO and prostaglandin production by melatonin might be responsible for its reversal of LPS-induced hyperthermia and adipsia.