A rat model of acute respiratory distress syndrome (ARDS) Part 2, influence of lavage volume, lavage repetition, and therapeutic treatment with rSP-C surfactant

The influence of lavage volume, and lavage repetition with physiological saline solution (groups 1-3: 3x4, 4x4, 5x4, groups 7-9: 3x8, 5x8, 7x8, mL per animal) was studied in a rat lung lavage model of the acute respiratory distress syndrome (ARDS). Anesthetized and tracheotomized rats (12 rats/group) were pressure-controlled ventilated with 100% oxygen at a respiratory rate of 30 breaths/min, inspiration: expiration ratio of 1:2, peak inspiratory pressure of 28 cm H2O at positive end-expiratory pressure of 8 cm H2O during the whole experimental period. To investigate the influence of therapeutic treatment, a recombinant surfactant protein C (rSP-C) containing surfactant was used. Therefore, rats which received a lavage of 4x4 mL per animal (groups 4 to 6) or 7x8 mL per animal (groups 10-12) were treated intratracheally with surfactant doses of 12.5, 25, or 100 mg phospholipids (PL) per kg body weight (bw). In all groups, partial arterial oxygen pressures (PaO2, mm Hg) and partial arterial carbon dioxide pressures (PaCO2, mm Hg) were determined 30 min before, directly after, and 5, 30, 60, 90, 120, 150, 180, and 210 min after the last lavage. Additionally, animals were euthanized 210 min after the last lavage for semiquantitative histopathological grading of coded lung slides. Grading was performed with respect to the severity of hyaline membrane formation (HM), margination and infiltration of polymorphonuclear neutrophil leukocytes (PMNL) into the lung alveoli and interstitial and intraalveolar edema (E). The intrapulmonary distribution of intratracheally applied rSP-C was estimated in selected lung slides stained with polyclonal anti-rSP-C antibody and was compared to unlavaged control rats and unlavaged rats which received 100 mg/kg bw rSP-C. The repetitive lavage depleted the lung from its natural surfactant resources leading to a pathophysiological cascade similar to that of the acute respiratory distress syndrome. PaO2 levels and HM formation showed a lavage-induced decrease. Both changes were significantly dependent on the repetition and volume of the lavage; however, the parameters PMNL and E did not show such a dependence. Treatment with rSP-C surfactant significantly improved oxygenation and reduced HM-formation in a dose-dependent manner independent from the lavage volume. All doses of rSP-C surfactant showed no clear influence on the parameters PMNL and E independently from the lavage volume. In lavaged rat lungs (ARDS-model), the exogenously applied rSP-C was distributed homogeneously along the alveolar lining. Unlavaged rats that received a similar dose of rSP-C showed a marked inhomogeneous extracellular distribution, mainly associated with larger bronchi, while the type II pneumocytes were stained positively in unlavaged control and unlavaged rSP-C treated rats. Conclusion: This model mimics very closely the wide spectrum of the clinical situation of human acute lung injury (ALI) because the variation of lavage volume and repetition lead to reproducible different severity grades and states of ALI. The significant reduction of pathognomic changes due to treatment with rSP-C surfactant showed that this is a useful model to estimate the influence of therapeutic concepts in ALI and ARDS.     

Comparison of rSP-C surfactant with natural and synthetic surfactants after late treatment in a rat model of the acute respiratory distress syndrome

1. In a previous paper we showed that an SP-C containing surfactant preparation has similar activity as bovine-derived surfactants in a rat lung lavage model of the adult respiratory distress syndrome. In this study surfactant was given ten minutes after the last lavage (early treatment). In the present investigation we were interested how different surfactant preparations behave when they are administered 1 h after the last lavage (late treatment).
2. Four protein containing surfactants (rSP-C surfactant, bLES, Infasurf and Survanta) were compared with three protein-free surfactants (ALEC, Exosurf and the phospholipid (PL) mixture of the rSP-C surfactant termed PL surfactant) with respect to their ability to improve gas exchange in this more stringent model when surfactant is given one hour after the last lavage. For better comparison of the surfactants the doses were related to phospholipids. The surfactants were given at doses of 25, 50 and 100 mg kg⁻¹ body weight. The surfactants were compared to an untreated control group that was only ventilated for the whole experimental period.
3. Tracheotomized rats (8–12 per dose and surfactant) were pressure-controlled ventilated (Siemens Servo Ventilator 900C) with 100% oxygen at a respiratory rate of 30 breaths min⁻¹, inspiration expiration ratio of 1 : 2, peak inspiratory pressure of 28 cmH₂O at positive endexpiratory pressure (PEEP) of 8 cmH₂O. Animals were ventilated for one hour after the last lavage and thereafter the surfactants were intratracheally instilled. During the whole experimental period the ventilation was not changed.
4. Partial arterial oxygen pressures (PaO₂, mmHg) at 30 min and 120 min after treatment were used for statistical comparison. All protein containing surfactants caused a dose-dependent increase of the reduced PaO₂ values at 30 min after treatment. The protein-free surfactants showed only weak dose-dependent increase in PaO₂ values at this time. This difference between the protein-containing and the protein-free surfactants was even more pronounced when comparing the PaO₂ values at 120 min after treatment. Only rSP-C surfactant, bLES and Infasurf showed a dose-dependent increase in PaO₂ at this time.
5. With this animal model of late treatment it is possible even to differentiate between bovine derived surfactants. The differences between protein-containing and protein-free surfactants become even more pronounced. From the comparison of rSP-C surfactant with bovine-derived surfactants and the PL surfactant without rSP-C, it can be concluded that addition of rSP-C is sufficient to achieve the same activity as that of natural surfactants.

     

Vitamin E influences the effects of fish oil on fatty acids and eicosanoid production in plasma and circulating cells in the rat

An EPA enriched oil (MaxEPA, Seven Seas, U.K. containing 18% EPA and 12% DHA) alone or supplemented with 10 mg/ml/alpha tocopherol, was administered by gastric intubation at the dose of 3.2 ml/kg/day for a period of eight weeks to male rats fed a standard diet. An additional group of animals was treated with the same amount of olive oil. The administration of MaxEPA alone resulted, as expected, in accumulation of EPA and reduction of AA levels in plasma, platelet, red blood cell and PMNL phospholipids, when compared to values in the olive oil group. In addition, levels of linoleic acid were elevated, suggesting inhibition of the conversion of linoleic to arachidonic acid. Formation of i.r. TxB2 by stimulated PRP, of i.r. 6-keto-PGF1 alpha by perfused aortas, and of IR LTB4 and C4 by stimulated PMNL were reduced, but production of superoxide anion by PMNL was enhanced by MaxEPA treatment vs the olive oil treatment. Supplementation of MaxEPA with vitamin E caused a smaller reduction of 20:4 levels and a smaller increase of 20:5 levels in plasma and cell phospholipids and modified the effects of MaxEPA on eicosanoid and superoxide anion production, suggesting that lipid peroxidation may mediate some of the biological effects of omega 3 fatty acids.     

Effects of Lung Surfactant Factor (LSF) Treatment on Gas Exchange and Histopathological Changes in an Animal Model of Adult Respiratory Distress Syndrome (ARDS): Comparison of Recombinant LSF with Bovine LSF

Summary: Repetitive lung lavage of adult rats leads to lung injury similar to ARDS resulting in poor gas exchange, protein leakage and infiltration of polymorphonuclear neutrophils (PMN) into the alveolar spaces (J Appl Physiol 1983; 55: 131-138). In a previous dose response comparison we have demonstrated that poor gas exchange could be improved by lung surfactant factor (LSF) instillation soon after lavage. Since Surfacten® (Tokyo Tanabe Co. Ltd., Tokyo, Japan) was described in vitro to inhibit PMN activity, we compared this preparation with a Recombinant LSF preparation (Byk Gulden, Konstanz, Germany; phospholipids plus human identical surfactant protein C) at doses of 25, 50 and 100 mg/kg body weight. Their efficacy was compared with an untreated control group with respect to improving gas exchange, inhibition of hyaline membrane formation and inhibition of the inflammatory response after multiple lavage. Tracheotomized rats were pressure-controlled ventilated (Siemens Servo Ventilator 900C, Sweden) with 100% oxygen at a respiratory rate of 30 breaths/min, inspiration:expiration ratio of 1:2, peak inspiratory pressure (PIP) of 28 cmH₂O at positive end-expiratory pressure (PEEP) of 8 cmH₂O. Two hours after LSF administration PEEP was reduced from 8 to 6 cmH₂O (first PEEP-reduction), from 6 to 3 (second reduction) and from 3 to 0 cmH₂O (third reduction) and finally raised to 8 cmH₂O. Results for the averaged partial arterial oxygen pressure [PaO₂ (mmHg)] of the 2 h period [PaO₂(5′-120′)] and for the PaO₂ during the second PEEP reduction [PaO₂(PEEP23/3)] were calculated. Both LSF preparations caused a dose-dependent increase of the PaO₂(5′-120′) and the PaO₂(PEEP23/3). Similarly, the formation of hyaline membranes was inhibited by both LSF preparations in a dose-dependent manner. Inhibition of the inflammatory response (infiltration of PMN) was not effected by either of the LSF preparations at any dose level. The described variations in ventilator settings are useful to evaluate the deflation stability and re-expansion potential of different LSF preparations. The reported results give evidence that prevention of atelectasis by LSF treatment improves gas exchange and inhibits formation of hyaline membranes, leading to the conclusion that LSF treatment may be a promising therapy in ARDS patients.     

Dexamethasone Reduced Clonidine-induced Hypoactivity in Mice

Reduced clonidine anti-nociception in mice given low doses of dexamethasone has encouraged us to investigate the effects of dexamethasone pretreatment on locomotor hypoactivity, another example of clonidine-induced behaviour in mice. Dexamethasone administered intraperitoneally (0.1, 1.0, 10 mg kg^?1) 30 min before clonidine reduced clonidine-induced locomotor hypoactivity in the activity cage to an extent which was dose-dependent. Dexamethasone administered centrally (10 ng/mouse) 30 min before clonidine was also able to reduce clonidine-induced locomotor hypoactivity. Cycloheximide administered at a dose of 10 mg kg^?1 2 h before clonidine did not change the effects of clonidine but was able to prevent the effects of dexamethasone on clonidine-induced hypoactivity. The glucocorticoid receptor antagonist RU38486 administered centrally at the dose of 1 ng/mouse did not change the effects of clonidine, whereas it was able to block the effects of dexamethasone on clonidine-induced locomotor hypoactivity. These results suggest that the effects of dexamethasone on clonidine-induced locomotor hypoactivity depend on the stimulating effects that dexamethasone exerts on the protein synthesis via the glucocorticoid receptor in the brain.     

The non-intubated, spontaneously breathing, continuous positive airway pressure (CPAP) ventilated pre-term lamb: a unique animal model

Neonatologists prefer non-invasive ventilation methods for pre-term neonates, who often require surfactant treatment. Therefore, a technology for non-invasive surfactant administration would be highly appreciated. We have developed a Continuous Powder Aerosolization (CPA) system for the generation of a humidified recombinant surfactant protein-C (rSP-C) surfactant aerosol for non-invasive administration to pre-term neonates via bi-nasal prongs. Before conducting clinical trials, safety testing in an adequate pre-clinical animal model is necessary. In contrast to existing pre-term lamb models, this model should use non-intubated animals to include upper airways for safety testing. Pre-term animals should have already a sufficient respiratory drive to breathe spontaneously on non-invasive continuous positive airway pressure (CPAP) support, but their lungs should still be pre-mature to be comparable with the clinical situation for the treatment of pre-term infants. The aim of this feasibility study was therefore to establish a CPAP-stable, non-intubated pre-term lamb model for the investigation of safety, efficacy, and pulmonary deposition of a humidified rSP-C surfactant aerosol. For this purpose, 19 pre-term lambs with a gestational age of 135-137 days (term: about 144 days) were delivered via Caesarean section. Four animals died before start of treatment, while the remaining animals were treated via customized bi-nasal prongs with rSP-C surfactant aerosol or humidified air as vehicle control. To determine pulmonary deposition, selected animals received rSP-C surfactant labelled with samarium oxide as non-radioactive tracer. Treatment was started at 30 min of age and was continued for 1 or 2.5 h. Investigations during the in-life phase included observation of clinical signs, haematology, blood gas analysis, and determination of minute volume. At 3 h of age, animals were euthanized and organs removed for histopathology investigation or for determination of pulmonary deposition. Administration of humidified, aerosolized rSP-C surfactant was well tolerated, and histopathology investigation of upper airways and lungs revealed no aerosol-related changes. Mean body weight-corrected pulmonary deposition of rSP-C surfactant ranged from 1.7 to 7.7 mg/kg depending on the duration of treatment and aerosolization parameters used. A trend towards reduced spontaneous minute volumes indicating reduced breathing efforts and towards reduced lung weights indicating less fluid in the lungs of surfactant-treated animals compared to animals of the vehicle control group could be seen. Taken together, a CPAP-stable, non-intubated pre-term lamb model was successfully established and the parameters for the investigation of safety, efficacy, and pulmonary deposition of aerosolized rSP-C surfactant for the subsequent main study were identified.     

Dexamethasone decreases lethality of rats in acute poisoning with T-2 toxin

T-2 toxin, a major trichothecene mycotoxin, was administered intravenously to rats. At a dose of 0.75 mg/kg two thirds of the animals died. In animals that received dexamethasone (1.6 mg/kg IV) either 30 min before or 1 h after the toxin, there was a more than fourfold reduction in lethality rate. Dexamethasone injected 3 h after the toxin was less effective.At a lethal dose of T-2 toxin (1 mg/kg IV) pretreatment with dexamethasone only delayed death, whereas lethality rate was barely affected (9/10 vs 10/10 in controls).Dexamethasone markedly reduced the incidence of lung edema and diarrhea. The incidence of hemorrhages, however, was not reduced by dexamethasone. Gastrointestinal bleeding was even more frequent in treated rats than in controls.     

血管内皮生长因子联合地塞米松对胎鼠肺泡Ⅱ型细胞的影响

目的研究联合使用血管内皮生长因子(VEGF)和地塞米松对胎鼠肺泡Ⅱ型细胞发育和肺泡表面活性物质结合蛋白B(SP-B)表达的影响，为防治早产儿呼吸窘迫综合征寻找新途径。方法取孕20 d的Wistar大鼠剖腹取胎鼠，原代培养肺泡Ⅱ型细胞，将所得肺泡Ⅱ型细胞分成4组，分别加入VEGF、地塞米松、VEGF＋地塞米松、空白培养液(即对照组)，孵育后测定各组胎鼠肺泡Ⅱ型细胞VEGF及其受体Flt-1、Flk-1和SP-B。结果VEGF组、地塞米松组与VEGF＋地塞米松组SP-B均阳性表达，对照组SP-B阴性表达；VEGF组与VEGF＋地塞米松组VEGF、Flt-1、Flk-1阳性表达，地塞米松组VEGF、Flt-1、Flk-1阴性表达。结论VEGF能促进肺泡发育和肺表面活性物质SP-B的合成与分泌，拮抗地塞米松下调肺泡Ⅱ型细胞受体表达的作用。     

Dexamethasone prevents acute cadmium-induced hepatic injury but exacerbates kidney dysfunction in rabbits

Cadmium is a potent hepatotoxicant for which neither effective preventive methods nor the mechanism of toxicity has been established. We investigated the preventive effect of dexamethasone against cadmium toxicity on cadmium-induced liver injury in rabbits. Pretreatment with dexamethasone at 1 mg/kg increased the rate of survival in rabbits administered 2.5 mg/kg iv cadmium. Cadmium induced acute severe liver injury characterized by hepatocellular necrosis, infiltration by inflammatory cells, and increases of plasma GOT, GPT, LDH, and LDH5. Dexamethasone mitigated the acute hepatotoxic effect of cadmium, but exacerbated cadmium-induced kidney dysfunction, with destruction of renal tubular cells and increases in excretion of protein, glucose, and amino acids into urine. The cadmium concentration in liver and kidney of rabbits administered cadmium was not changed by dexamethasone pretreatment. Although metallothionein mRNA expression induced by cadmium was not affected by dexamethasone in liver or kidney, cadmium-induced metallothionein protein production was augmented at the early phase in liver and decreased at the later phase in kidney. Neutrophilia observed after cadmium administration was enhanced initially by dexamethasone pretreatment. These results indicate that dexamethasone pretreatment potently prevented cadmium-induced liver injury, but exacerbated renal tubular dysfunction.     

The interaction of peripherally and centrally administered dexamethasone and RU 38486 on morphine analgesia in mice.

1. Dexamethasone or RU 38486 were administered intraperitoneally or intracerebroventricularly to mice 10 or 120 min before morphine administration. The interaction of these drugs with the analgesic effects of morphine was examined using the hot plate test. 2. Dexamethasone i.p. pretreatment reduced analgesic responses to morphine injected 120 min but not 10 min after dexamethasone; i.c.v. injection of dexamethasone 10 and 120 min before morphine administration was effective in reducing morphine analgesia. 3. RU 38486 i.c.v. pretreatment (but not i.p. pretreatment) performed 120 (but not 10) min before morphine administration enhanced morphine analgesic effects. 4. These results, particularly the effects of drug interaction for i.c.v. administration, strongly confirm a central site for dexamethasone and RU 38486 action.     

Dual action of glucocorticoid hormones on the gastric mucosa: how the gastroprotective action can be transformed to the ulcerogenic one

Glucocorticoid hormones have dual action on the stomach: gastroprotective and ulcerogenic one. The present study was designed to investigate how physiological gastroprotective action of glucocorticoids can be transformed to pathological ulcerogenic effect. Dose- and time-dependent effects of single injection of dexamethasone on indomethacin-induced gastric erosions, corticosterone and blood glucose levels, somatic parameters were investigated in rats. Dexamethasone at the doses of 0.1, 1, 10 mg/kg decreased the gastric erosion area dose dependently in the case of its injection 1 h before indomethacin administration. Gastroprotective action of dexamethasone (at a dose of 1 mg/kg) was also observed in the case of its injection 6 and 12 h before indomethacin. However, the further increase in the time interval caused transformation of gastroprotective action of dexamethasone to ulcerogenic one. Accordingly to the data obtained short-term maintenance of blood glucose level provides the gastroprotective action of dexamethasone, while dexamethasone-induced long-lasting maintenance of blood glucose level accompanied with the signs of catabolic effects may be responsible at least partly for its ulcerogenic effect. Received 15 October 2008; accepted 7 November 2008     

The effect of dexamethasone on tissue fibrinolytic system in male and female rats.

BACKGROUND: Dexamethasone in low and high doses affects blood fibrinolytic activity both in animals and humans. In this study the effect of a high dose of dexamethasone on plasminogen activator activity (PAA), t-PA antigen level, plasminogen activator inhibition (PAI) and plasmin inhibition (Pl) in rat heart, brain, liver, lungs and kidneys was investigated in both sexes. MATERIALS AND METHODS: Twenty male and twenty female adult Wistar rats were used. Dexamethasone was administered as a single intraperitoneal injection (3mg/kg/day) in rats, once daily, for a period of 5 consecutive days. t-PA antigen level was assayed by an enzyme-linked immunoabsorbant assay method. PAA, PAI and Pl were determined by spectrophotometric methods. The plasminogen used was isolated from rat plasma. RESULTS: Dexamethasone induced variable changes in the fibrinolytic parameters in rat heart, brain and liver of both sexes; in lungs and kidneys dexamethasone had no effect. CONCLUSION: These changes of PAA, PAI and t-PA antigen level in heart, brain and liver induced by dexamethasone might be of importance regarding the involvement of glucocorticoids and plasminogen activators/plasmin in many pathophysiological conditions.     

Glucocorticoids reverse IL-1beta-induced impairment of beta-adrenoceptor-mediated relaxation and up-regulation of G-protein-coupled receptor kinases

1. The aim of the present study was to examine the effects of glucocorticoid dexamethasone on airway responsiveness to albuterol after intratracheal instillation of saline or IL-1beta in Brown-Norway rats in vivo and to elucidate the molecular mechanism of this effect. 2. IL-1beta caused a significant reduction in albuterol-mediated relaxation to protect against MCh-induced bronchoconstriction. Dexamethasone attenuated the IL-1beta-induced impaired relaxation while alone had no effect when compared to rats treated identically with saline. 3. The density of beta(2)-adrenoceptors was significantly reduced in lung membranes harvested from IL-1beta-treated rats, which was associated with impaired isoproterenol- and forskolin-stimulated cyclic AMP accumulation and adenylyl cyclase (AC) activity ex vivo. Dexamethasone did not prevent IL-1beta-induced down-regulation of beta(2)-adrenoceptors but completely blocked IL-1beta-induced impairment of cyclic AMP accumulation and AC activity stimulated by isoproterenol and forskolin. 4. The inhibitory G-protein subtypes, G(ialpha1), G(ialpha2) and G(ialpha3), were detected in lung membranes prepared from all groups of rats but the intensity of G(ialpha1) and G(ialpha2) was markedly increased in IL-1beta-treated rats, which were not prevented by dexamethasone. 5. The activity of cytosolic GRK and the expression of GRK2 and GRK5 were elevated in the lung of IL-1beta-treated rats, which were completely abolished by dexamethasone. 6. These results indicate that treatment of rats with IL-1beta results in desensitization of pulmonary beta(2)-adrenoceptors. In light of data obtained in this study, we propose that both the decrease in AC activity and the increase in GRK activity, which are reversed by dexamethasone, may underlie beta(2)-adrenoceptor desensitization.     

Modulation of the acute phase response and in vitro measurement of interleukin-1 activity following administration of dexamethasone to adjuvant-arthritic rats

Adjuvant-arthritic (AA) rats were medicated with dexamethasone to determine if this glucocorticoid suppressed the activity of interleukin-1 (IL-1) or the acute phase response. Dexamethasone (0.1 mg/kg, p.o.) administered daily for two weeks to AA rats, significantly (p less than or equal to 0.01) decreased high splenic IL-1 production (60% inhibition). Dexamethasone at a 0.5 mg/kg dose reduced AA rat splenic IL-1 production below normal (100% inhibition). In addition, dexamethasone significantly inhibited the AA rat acute phase response as measured by reduction of plasma C-reactive protein levels and enhancement of plasma albumin and iron levels. Following medication with 0.02, 0.1 or 0.5 mg/kg dexamethasone, high plasma C-reactive protein levels decreased by 33, 77 and 95% respectively, compared to untreated AA controls. Under the same dosing regimen of 0.02, 0.1 or 0.5 mg/kg dexamethasone, plasma albumin levels increased by 44, 128 and 239% respectively, while plasma iron levels rose by 19, 64 and 98% respectively, compared to AA controls. At the 0.02, 0.1 and 0.5 mg/kg doses dexamethasone also significantly reduced injected and noninjected paw swelling in AA rats. In view of the ability of dexamethasone to decrease IL-1 production and the acute phase response often associated with it, it is possible that part of the anti-inflammatory activity of dexamethasone may stem from inhibition of IL-1 formation in vivo.     

Clonidine-induced antinociception and locomotor hypoactivity are reduced by dexamethasone in mice

The effects of dexamethasone pretreatment on clonidine-induced antinociception and locomotor hypoactivity were investigated in mice. In the hot-plate and the tail-flick tests, dexamethasone administered intraperitoneally at a dose of 1 mg kg(-1), 30 or 60 min before clonidine, reduced clonidine antinociception in both tests and reduced clonidine-induced locomotor hypoactivity in the activity cage. When administered 15 min before clonidine, dexamethasone had no effect on clonidine antinociception. A higher dexamethasone dose (10 mg kg(-1)) induced the same effects observed at a dose of 1 mg kg(-1) in the hot-plate and the tail-flick tests, but the former dose had a stronger effect on locomotor hypoactivity. Dexamethasone (10 ng/mouse) administered intracerebroventricularly 30 min before clonidine was also able to reduce both clonidine-induced antinociception and locomotor hypoactivity. The protein synthesis inhibitor, cycloheximide, administered intraperitoneally at the dose of 10 mg kg(-1), 2 h before clonidine, was able to prevent dexamethasone effects on clonidine-induced antinociception. The glucocorticoid receptor antagonist RU-38486, administered intracerebroventricularly at the dose of 1 ng/mouse, was also able to block dexamethasone effects on clonidine-induced antinociception and locomotor hypoactivity, whereas both cycloheximide and RU-38486 per se did not influence pain sensitivity or locomotor activity. These results suggest that the dexamethasone effects on clonidine-induced antinociception and locomotor hypoactivity depend on the stimulating effects that dexamethasone exert, on the protein synthesis via the glucocorticoid receptor in the brain.     

A comparison of the carrageenan edema test and ultraviolet light-induced erythema test as predictors of the clinical dose in rheumatoid arthritis.

Twelve non-steroidal anti-inflammatory agents (NSAI's) and one steroidal anti-inflammatory agent, dexamethasone, were examined in the carrageenan edema test (CET) in the rat and in the ultraviolet light-induced erythema test (UVE) in the guinea pig to evaluate the correlation between those models of inflammation and the clinical dose of the NSAI's in the treatment of rheumatoid arthritis. The regression of the logarithm of the clinical dose with the logarithm of the ED50 for UVE gave a slope of 0.54 implying a non-parallelism of assays and a difference in mechanism. Dexamethasone failed to inhibit the UVE thereby corroborating this point. The parallelism of the logarithm of the clinical dose with the logarithm of the ED50 for the CET was substantially better (slope = 0.86). Dexamethasone was active in CET and its dose would be predicted by the CET regression. When only one variable was used for a prediction, log(CET) was a better predictor of log (clinical dose) than log(UVE). Standard methods for best regression selection indicated that even when both predictor variables were considered, log(CET) alone gave the best regression equation for predicting clinical dose. The view that inhibition of prostaglandin biosynthesis is the primary anti-inflammatory mechanism of NSAI's in rheumatoid arthritis is discussed in terms of these findings.     

Effect of particle emissions from biofuel combustion on surface activity of model and therapeutic pulmonary surfactants

This study was designed to determine the effects of particle emissions from biofuel combustion in household cooking devices, commonly used in rural India, on surface activity of model lung surfactants using Langmuir monolayers. The effect of wood and dried particles from combustion of cowdung on the surface activity of model lung surfactant dipalmitoylphosphatidylcholine (DPPC), DPPC:PG (phosphatidyl glycerol) 7:3 and the therapeutic surfactant, Exosurf, were evaluated. Dried particles from combustion of cowdung in 50 wt.% mixture with DPPC elevated the γ_min to 15.08 ± 1.28 mN/m and 50 wt.% particles from combustion of wood increased minimum surface tension γ_min to 13.46 ± 1.70 mN/m from a zero value for DPPC alone. A graded response of inhibitory potential for all three surfactants with increasing doses was found for each type of particles. An increase in the minimum surface tension achieved by surfactants in the presence of biofuel particles implies surfactant dysfunction, a greater tendency of alveolar collapse in vivo on exposure to biofuel emissions and can lead to respiratory distress.     

Dexamethasone reduces methotrexate biliary elimination and potentiates its hepatotoxicity in rats

Increased hepatotoxicity of methotrexate has been reported during dexamethasone therapy in humans. Despite the observed inducing effect of dexamethasone on some methotrexate transporting proteins in the liver, the kinetic aspects of this interaction have not been studied yet. Thus, the aim of the present study was to evaluate the influence of dexamethasone on the hepatic and overall pharmacokinetics of methotrexate. Pharmacokinetics of methotrexate was evaluated in rats during an in vivo steady-state clearance study after either single intravenous dose of dexamethasone or its four-day oral administration in a dose optimized for transport proteins induction. Dexamethasone oral pretreatment reduced biliary clearance of methotrexate by 53%. Although liver tissue concentration of methotrexate increased only slightly in these animals, a significant increase in liver weights produced by dexamethasone pretreatment revealed a marked increase in liver content of the drug. An evaluation of plasma liver enzyme activities measured before and after methotrexate administration demonstrated a potentiation of corticosteroid hepatotoxicity by the cytostatic. Analysis of methotrexate transporter expression in the liver showed up-regulation of Mrp2, Oatp1a4, and Oat2, and down-regulation of Mrp3. These observations comply with increased biliary excretion and reduced plasma concentrations of their endogenous substrate, conjugated bilirubin. In contrast, single intravenous bolus of dexamethasone did not influence any pharmacokinetic parameter of methotrexate. In conclusion, these results indicate that hepatocellular impairment associated with reduced biliary elimination of methotrexate, and its raised liver content may contribute to increased hepatotoxicity of the drug when co-administered with dexamethasone. Moreover, an influence of dexamethasone on protein expression of anionic drugs transporters in the liver and kidney was demonstrated.     

米诺地尔联合地塞米松对肾缺血再灌注损伤大鼠肾功能指标和氧化应激指标的影响

目的探究米诺地尔联合地塞米松对肾缺血再灌注损伤大鼠肾功能指标和氧化应激指标的影响。方法 40只SD大鼠通过ip 1%戊巴比妥钠溶液4 mg/kg建立肾缺血再灌注损伤模型,分为假手术组、模型组、地塞米松组、米诺地尔组、米诺地尔联合地塞米松组,每组8只。假手术组不进行肾缺血再灌注处理;模型组术前30 min ip生理盐水1 mL;地塞米松组术前30 min ip 4 mg/kg地塞米松磷酸钠注射液;米诺地尔组术前30 min ip 0.6 mg/kg米诺地尔;米诺地尔联合地塞米松组术前30 min ip 0.3 mg/kg米诺地尔和2 mg/kg地塞米松磷酸钠注射液。考察米诺地尔联合地塞米松对肾缺血再灌注损伤大鼠肾功能指标和氧化应激指标的影响。结果地塞米松组、米诺地尔组、米诺地尔联合地塞米松组的血清尿素氮(BUN)、肌酐(Cr)值和肾组织丙二醛(MDA)值均显著低于模型组(P0.05、0.01),以米诺地尔联合地塞米松组最为显著(P0.01);肾组织匀浆总超氧化物歧化酶(T-SOD)活性均显著高于模型组(P0.01),以米诺地尔联合地塞米松组最为显著(P0.01)。结论地塞米松和米诺地尔预处理均可以显著减轻急性肾缺血再灌注的损伤,且两者对急性肾缺血再灌注损伤的保护作用总体相近,联合用药预处理的保护作用则更加显著。