Effect of probiotics in experimental otitis media with effusion.

OBJECTIVES: The article's aim was to investigate the effects of probiotics in the experimental otitis media with effusion. MATERIALS AND METHODS: Twenty-four male Wistar albino rats were used. They were divided into four groups. Experimental otitis media with effusion was created by intratympanic histamine injection. The effusion was confirmed by otomicroscopic examination 24 h after injection. Group 1; did not receive any treatment, group 2; received probiotics for 7 days after the detection of effusion, group 3; received probiotics for 7 days prior to injection of histamine, group 4; received probiotics for 7 days before injection of histamine and 7 days after detection of effusion. After detection of effusion, animals were sacrificed. Otomicroscopic evaluation was done to determine the effusion. In histopathological examination neutrophil leukocyte counts were determined in 25 areas of the sub-mucosa of the temporal bulla. RESULTS: The otomicroscopic ear effusions' healing rate in group 1 was 10%, in group 2 was 25%, in group 3 was 50%, and in group 4 was 100% (p < 0,013). The mean counts of submucosal neutrophil leukocyte from 25 areas of the temporal bulla of group 1 was 86,8 ± 24, group 2 was 66,5 ± 21, group 3 was 66,2 ± 16, and group 4 was 26,3 ± 6,5 (p < 0,001). CONCLUSION: Probiotics have a curative effect on the prevention and treatment of otitis media with effusion. This result may be related to their anti-inflammatory effects. Therefore, probiotics can be widely used in the age group at risk for otitis media with effusion as a complementary therapy by dietary supplements. LEVEL OF EVIDENCE: NA.

The anti-inflammatory effects of erythromycin, clarithromycin, azithromycin and roxithromycin on histamine-induced otitis media with effusion in guinea pigs.

BACKGROUND: Otitis media with effusion is a clinical manifestation characterised by inflammation of middle-ear mucosa. This study investigated the therapeutic effect of erythromycin, clarithromycin, azithromycin and roxithromycin on a histamine-induced animal model of otitis media with effusion. METHODS: The animals were divided into five groups, receiving erythromycin, clarithromycin, azithromycin, roxithromycin or saline solution. The guinea pigs in the study groups received erythromycin (40 mg/kg/day), clarithromycin (15 mg/kg/day), azithromycin (10 mg/kg/day) or roxithromycin (10 mg/kg/day) for 3 days by gastric tube. Four hours after the end of the administration, histamine solution was injected into the right middle ear. RESULTS: The lowest neutrophil density value obtained using stereological techniques was in the azithromycin group (0.86 ± 0.25 × 10-5/µm3), while the highest value was observed in the control group (6.68 ± 3.12 × 10-5/µm3). The anti-inflammatory properties of clarithromycin, azithromycin and roxithromycin were similar to one another, but better than that of erythromycin. CONCLUSION: The use of macrolide antibiotics is recommended, as they show antibacterial and anti-inflammatory efficacy in otitis media with effusion.

Effect of systemic clarithromycin and prednisolone on histamine-induced otitis media in guinea pigs.

CONCLUSION: The results of the study showed that clarithromycin has anti-inflammatory and antioxidant effects and, when it is combined with prednisolone, those effects gain strength. OBJECTIVES: The present study aims to investigate the effects that the antioxidant and anti-inflammatory activities of clarithromycin and/or prednisolone have on experimental otitis media in effusion-induced guinea-pigs. METHOD AND RESULTS: In this study, 35-male guinea pigs were randomly divided into five-groups. For the experimental otitis media, intra-tympanic histamine (0.1 ml) was injected into the guinea pigs in all of the groups except the control group. Then, 24-h after the intra-tympanic injections, clarithromycin (15 mg/kg/day) and/or prednisolone (1 mg/kg/day) were applied intraperitoneally to the guinea-pigs for 7-days. The biochemical analysis showed an increase in antioxidant capacity and a decrease in oxidant status and malondialdehyde (MDA) levels in the clarithromycin group and the prednisolone group and especially in the clarithromycin+prednisolone group, as compared to the experimental group (p < 0.05). In the cytokine analysis, lower levels of interleukin (IL)-6 and IL-17A and higher IL-10 were found in the clarithromycin, prednisolone, and clarithromycin+prednisolone groups than in the experimental group (p < 0.05). Furthermore, the histologic analyses showed histopathologic changes in the middle ear mucosa of the experimental group, but comparatively fewer-histopathologic changes were observed in the clarithromycin, prednisolone, and clarithromycin+prednisolone groups.

Pathological study of otitis media with effusion after treatment with intranasal pulmonary surfactant.

OBJECTIVES/HYPOTHESIS: To evaluate the histopathological effect of intranasal pulmonary surfactant (PS) on the eustachian tube (ET) in guinea pigs with otitis media with effusion (OME). STUDY DESIGN: Randomized control trial. METHODS: Nonviable heat-killed Hemophilus influenzae solution was injected into the tympanum of guinea pigs by a trans-eardrum approach to establish OME. Guinea pigs were divided into four groups: normal controls (group A), untreated OME (group B), saline-treated (group C), PS-treated (group D). The response threshold of the guinea pigs was measured by auditory brainstem response (ABR), and data were analyzed by one-way analysis of variance. The histopathological changes in the osseous, cartilaginous, and muscular portions of the ET were observed systematically by light microscopy. RESULTS: The ABR threshold in OME group B was raised significantly compared with normal group (A). The response in saline-treated group C was not statistically significantly different compared with OME group B. Seven days after intranasal dripping of pulmonary surfactant in PS-treated group D, the response threshold showed at statistically significant decrease compared with OME B and saline-treated C groups. In OME group B and saline-treated group C, mucosa showed swelling with goblet cell hyperplasia, and cilia were irregularly arranged. In PS-treated group D, there was slight mucosal swelling with fewer goblet cells, and cilia were regularly arranged, similar to the normal group A. CONCLUSIONS: The findings of the study indicate that intranasal pulmonary surfactant drops have protective and hyposecretory effects on the mucociliary system of the ET in guinea pigs suffering from OME.

The conductive hearing loss due to an experimentally induced middle ear effusion alters the interaural level and time difference cues to sound location.

Otitis media with effusion (OME) is a pathologic condition of the middle ear that leads to a mild to moderate conductive hearing loss as a result of fluid in the middle ear. Recurring OME in children during the first few years of life has been shown to be associated with poor detection and recognition of sounds in noisy environments, hypothesized to result due to altered sound localization cues. To explore this hypothesis, we simulated a middle ear effusion by filling the middle ear space of chinchillas with different viscosities and volumes of silicone oil to simulate varying degrees of OME. While the effects of middle ear effusions on the interaural level difference (ILD) cue to location are known, little is known about whether and how middle ear effusions affect interaural time differences (ITDs). Cochlear microphonic amplitudes and phases were measured in response to sounds delivered from several locations in azimuth before and after filling the middle ear with fluid. Significant attenuations (20-40 dB) of sound were observed when the middle ear was filled with at least 1.0 ml of fluid with a viscosity of 3.5 Poise (P) or greater. As expected, ILDs were altered by ~30 dB. Additionally, ITDs were shifted by ~600 µs for low frequency stimuli (<4 kHz) due to a delay in the transmission of sound to the inner ear. The data show that in an experimental model of OME, ILDs and ITDs are shifted in the spatial direction of the ear without the experimental effusion.

Can Helicobacter pylori cause inflammation in the middle ear?

OBJECTIVES: To investigate whether Helicobacter pylori causes inflammation in the normal middle ear and in the middle ear with effusion. METHODS: Sixteen adult New Zealand white rabbits were divided into two gropus equally. Group I was representing histamine-induced middle ear inflammation and Group II was representing normal middle ear. While H. pylori was inoculated in the right ears, physiologic saline was inoculated in the left ears of the rabbits in both groups. Results were evaluated clinically, histopathologically and microbiologically. Fisher's exact test was used for statistical analysis. RESULTS: In Group I, clinical scores of the inflammation in the right ears were higher than the left ears scores at the 7th day. Histopathological scores of the inflammation in the right ears were higher than the left ears scores at the 7th day. Also, H. pylori was isolated in 6 of the 8 right ears of the rabbits. In Group II, while clinical scores of the inflammation in the right ears scores were higher than the left ears scores at the 7th day, histopathological scores were not significantly different between both ears. Also, no H. pylori was isolated in right ears of the rabbits. CONCLUSIONS: Effusion in the middle ear induced by histamine is an appropriate medium for H. pylori reproduction and it also aggravates the inflammation process. In contrary, H. pylori did not cause inflammation in the normal middle ear. We suggest that H. pylori does not play a role in the etiology of otitis media with effusion alone, but it contributes to the inflammation process in the presence of an effusion.

Effect of ciprofloxacin/dexamethasone versus ciprofloxacin/hydrocortisone on lipopolysaccharide-induced experimental otitis media.

OBJECTIVES: The purpose of this study is to compare the effect of topical ciprofloxacin/dexamethasone versus topical ciprofloxacin/hydrocortisone on the outcome of lipopolysaccharide (LPS)­induced otitis media with effusion in chinchillas. STUDY DESIGN: A randomized experimental animal study. SETTING: Jerry L. Pettis Veteran's Medical Center. SUBJECTS AND METHODS: Otitis media with effusion was induced in 5 groups of chinchillas, 6 per group, by injecting 0.3 mL (1 mg/mL) of Salmonella enteric LPS into the superior bullae of each chinchilla with a venting needle in place. Each group was treated with 0.2 mL of test substance at ­2, 24, 48, and 72 hours relative to the 0-hour LPS induction. Group 1 was treated with vehicle control. Groups 2 to 5 received 0.3% ciprofloxacin with either 0.1% dexamethasone (group 2), 1% dexamethasone (group 3), 0.1% hydrocortisone (group 4), or 1% hydrocortisone (group 5). The outcome of each treatment was measured by the amount of middle ear effusion present and mucosal thickness at 120 hours posttreatment. RESULTS: Ciprofloxacin/dexamethasone 1% significantly (P = .0150) reduced middle ear effusion compared with control. Ciprofloxacin/dexamethasone 1% significantly reduced the mucosal thickness when compared with vehicle control (P = .0005), ciprofloxacin/dexamethasone 0.1% (P = .0240), and ciprofloxacin/hydrocortisone 0.1% (P = 1.00). Results also showed a dose-response effect between the ciprofloxacin/dexamethasone concentrations. CONCLUSIONS: This study demonstrated that treatment with a combination of topical ciprofloxacin and corticosteroid decreased the middle ear effusion when compared with the control group and that ciprofloxacin/dexamethasone suspension reduced the severity of LPS-induced experimental otitis media more than ciprofloxacin/hydrocortisone did.

Effect of middle ear fluid on sound transmission and auditory brainstem response in guinea pigs.

Combined measurements of middle ear transfer function and auditory brainstem response (ABR) in live guinea pigs with middle ear effusion (MEE) are reported in this paper. The MEE model was created by injecting saline into the middle ear cavity. Vibrations of the tympanic membrane (TM), the tip of the incus, and the round window membrane (RWM) were measured with a laser vibrometer at frequencies of 0.2-40 kHz when the middle ear fluid increased from 0 to 0.2 ml (i.e., full fill of the cavity). The click and pure tone ABRs were recorded as the middle ear fluid increased. Fluid introduction reduced mobility of the TM, incus and RWM mainly at high frequencies (f > 1 kHz). The magnitude of this reduction was related to the volume of fluid. The displacement transmission ratio of the TM to incus varied with frequency and fluid level. The volume displacement ratio of the oval window to round window was approximately 1.0 over most frequencies. Elevation of ABR thresholds and prolongation of ABR latencies were observed as fluid level increased. Reduction of TM displacement correlated well with elevation of ABR threshold at 0.5-8 kHz. Alterations in the ratio of ossicular displacements before and after fluid induction are consistent with fluid-induced changes in complex ossicular motions.

Accuracy of velocity distortion product otoacoustic emissions for estimating mechanically based hearing loss.

Distortion product otoacoustic emissions (DPOAEs) measured as vibration of the human eardrum have been successfully used to estimate hearing threshold. The estimates have proved more accurate than similar methods using sound-pressure DPOAEs. Nevertheless, the estimation accuracy of the new technique might have been influenced by endogenous noise, such as heart beat, breathing and swallowing. Here, we investigate in an animal model to what extent the accuracy of the threshold estimation technique using velocity-DPOAEs might be improved by reducing noise sources. Velocity-DPOAE I/O functions were measured in normal and hearing-impaired anaesthetized guinea pigs. Hearing loss was either conductive or induced by furosemide injection. The estimated distortion product threshold (EDPT) obtained by extrapolation of the I/O function to the abscissa was found to linearly correlate with the compound action potential threshold at the f(2) frequency, provided that furosemide data were excluded. The standard deviation of the linear regression fit was 6 dB as opposed to 8 dB in humans, suggesting that this accuracy should be achievable in humans with appropriate improvement of signal-to-noise ratio. For the furosemide animals, the CAP threshold relative to the regression line provided an estimate of the functional loss of the inner hair cell system. For mechanical losses in the middle ear and/or cochlear amplifier, DPOAEs measured as velocity of the umbo promise an accuracy of hearing threshold estimation comparable to classical audiometry.

[The expression and significance of NF-kappaB in the rat model of otitis media with effusion experimentally induced by ovalbumin].

OBJECTIVE: To investigate the T helper cells (Th) predominant differentiation and the modulation of nuclear transcription factors kappa B (NF-kappaB) in middle ear of rat model of otitis media with effusion (OME). METHOD: Sixteen SD rats were randomly divided into OME (Exp group) and control group (Con group). The expression of NF-kappaB were observed by immunohistochemistry. The level of IFN-gamma and IL-4 in tympanic lavage fluid (TLF) were determined by ELISA. RESULT: As compared to the Con group , the level of IL-4 and the ratio of Th2/Th1 (IL-4/IFN-gamma) in TLF of Exp group significantly increased (P<0.05), when no significant difference in IFN-gamma levels in TLF was found. The ratio of NF-kappaB p65 positive cells to white cells in temporal bone marrow smears and middle ear mucosa of Exp group was significantly higher than that of Con group (P<0.05). The expression of NF-kappaB p65 in temporal bone marrow smears and middle ear mucosa was signficantly positively correlated with the concentration of IL-4 in TLF of Exp group (P<0.05). CONCLUSION: The middle ear is capable of mounting an allergic response and subsequent formation of effusion. There is Thl/Th2 immune response imbalance, which polarizes toward Th2 response in the middle ear microenvironment of allergic OME rat model. Moreover , NF-kappaB may participate in regulating Th2 predominant reaction.

Change of middle ear transfer function in otitis media with effusion model of guinea pigs.

Otitis media with effusion (OME) is an inflammatory disease of the middle ear that causes most cases of conductive hearing loss observed in the pediatric population. With the long term goal of evaluating middle ear function with OME, the aim of the current study was to create an animal model of OME in which middle ear transfer functions could be measured. In guinea pigs, OME was created by injecting lipopolysaccharide (LPS) into the middle ear. Evidence of OME was assessed by otoscopy, tympanometry, histology, and by measuring the volume of fluid in the middle ear. Vibrations of the umbo and round window membrane were measured with a laser Doppler vibrometer at frequency range of 200-40 kHz in three groups of 3, 7, and 14 days after injection of LPS. Changes in displacement of the umbo and round window membrane in response to 80 dB SPL sound in the ear canal were measured across the frequency range. Displacement of both the umbo and round window membrane was reduced at all time points following LPS injections. Further, the change of the displacement transmission ratio (DTR) from the tympanic membrane to the round window occurred mainly in chronic (e.g. 14 days post-LPS injection) OME ears. This study provides useful data for analyzing the change of middle ear transfer function in OME ears.

Up-regulation of macrophage migration inhibitory factor induced by endotoxin in experimental otitis media with effusion in mice.

CONCLUSION: Injection of endotoxin into the middle ear causes production of macrophage migration inhibitory factor (MIF) in an experimental mouse model of otitis media with effusion (OME). Down-regulation of MIF may become a new approach for the management of OME. OBJECTIVE: To determine the role of MIF in OME. MATERIALS AND METHODS: Mice were divided into two groups and their middle ears were injected with either endotoxin or phosphate-buffered saline (PBS). Mice were sacrificed at 6 h, 12 h, or 1, 3, 7, or 14 days after injection and concentrations of MIF, interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) in middle ear effusions were measured by enzyme-linked immunosorbent assay. RESULTS: Concentrations of MIF in the endotoxin group at 1 day and 3 days were significantly higher than in the PBS control group. Concentrations of IL-1beta in the endotoxin group at 6 h, 12 h, 1 day, and 3 days were significantly higher than in controls. Concentrations of TNF-alpha in the endotoxin group at 1 day and 3 days were significantly higher than in controls. Concentration of MIF in the endotoxin group was positively correlated with that of IL-1beta and TNF-alpha.

Immune modulatory oligonucleotides in prevention of nasal allergen-induced Eustachian tube dysfunction in rats.

OBJECTIVES: Develop a model of nasal allergen-induced Eustachian tube dysfunction (ETD) in a rat and investigate the role of immune modulatory oligonucleotides (IMOs) in the prevention of nasal allergen-induced ETD. STUDY DESIGN AND SETTING: Prospective, randomized study. Brown Norway rats were sensitized to ova albumin (OVA) and randomized to receive pretreatment with IMOs or phosphate-buffered saline. All animals were challenged intranasally with aerosolized OVA. Dynamic measures of Eustachian tube (ET) function were analyzed. RESULTS: Animals that were OVA-sensitized and IMO-pretreated had significantly lower mean passive opening (95% confidence interval [95% CI] 15.0,19.4) and closing (95% CI 4.8,7.8) ET pressures compared with those of (95% CI 24.1,32.7) and (95% CI 12.1,18.8) OVA-sensitized untreated rats, respectively. In addition, the IMO-pretreated animals demonstrated the ability to actively clear a significantly higher proportion of negative pressure (95% CI 0.64,0.96) compared with the untreated animals (95% CI 0.09,0.39). IMO-pretreated animals also demonstrated significantly improved mean mucociliary clearance times in seconds (95% CI 115,195) than those in untreated animals (95% CI 308,668). CONCLUSIONS: Pretreatment with IMOs prevented allergen-induced allergic inflammation around the Eustachian tube (ET) and resulted in improved ventilatory function of the ET compared with sensitized untreated animals. IMOs offer considerable promise in the management of nasal allergic disease as well as otitis media with effusion.

Immune modulatory oligonucleotides in the prevention and treatment of OVA-induced eustachian tube dysfunction in rats.

BACKGROUND: Otitis media with effusion (OME) is often associated with allergies. Immune modulatory oligonucleotides (IMO) mediate allergic inflammation and may therefore be efficacious in the treatment of airway inflammation. OBJECTIVE: To evaluate the role of an IMO via transtympanic mucosal application in prevention and treatment of ovalbumin-induced OME. DESIGN: Forty brown Norway rats were divided into control and treatment groups. Eustachian tube dysfunction was evaluated by passive opening pressures, passive closing pressures, active clearance of negative pressure, and mucociliary clearance transit time. RESULTS: Rats who underwent IMO treatment required 50% less pressure to open and close the eustachian tube (P < 0.05) and were able to actively clear 50% more negative pressure than the ovalbumin-control rats (P < 0.001). The treatment rats' mucociliary clearance time was half that of the control group (P < 0.001). CONCLUSION: IMO via transtympanic application can prevent and treat allergy-induced eustachian tube dysfunction in rats. IMO may offer substantial promise in the future management of OME.

Effects of tumor necrosis factor alpha antagonist, platelet activating factor antagonist, and nitric oxide synthase inhibitor on experimental otitis media with effusion.

OBJECTIVES: We studied the inflammatory responses in otitis media with effusion induced by lipopolysaccharide (LPS) in rats, and compared the preventive effects of tumor necrosis factor (TNF) soluble receptor type I (sTNFRI, a TNF-alpha antagonist), platelet activating factor antagonist, and the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). METHODS: We used 2 control groups of Sprague Dawley rats (untreated and saline-treated) and 4 experimental groups, which all received an intratympanic injection of LPS, followed in 3 groups by experimental treatment of the same ear. The LPS group had no additional treatment. The L-NAME group received intraperitoneal injection of L-NAME and was reinjected after 12 hours. The A-85783 group was first given an intraperitoneal injection of A-85783. The sTNFRI group was first given an intratympanic injection of sTNFRI. Twenty-four hours after the initial intratympanic injection of LPS, temporal bones from each group were examined histopathologically and the vascular permeability of the middle ear mucosa was measured by Evans blue vital dye staining. RESULTS: The L-NAME, A-85783, and sTNFRI groups showed significantly reduced capillary permeability, subepithelial edema, and infiltration of inflammatory cells in comparison with the LPS group. There were no differences in capillary permeability, subepithelial edema, or infiltration of inflammatory cells between the A-85783 and sTNFRI groups. The L-NAME group showed no difference in vascular permeability or subepithelial edema in comparison with the A-85783 and sTNFRI groups, but showed more infiltration of inflammatory cells. CONCLUSIONS: We conclude that sTNFRI, A-85783, and L-NAME can be proposed as alternative future treatments for otitis media with effusion. However, L-NAME may be the least effective of these agents.

The role of immunomodulatory oligonucleotides in prevention of OVA-induced Eustachian tube dysfunction.

OBJECTIVE: To evaluate the potential role of immunomodulatory oligonucleotides (IMO) in the prevention of OVA-induced Eustachian tube dysfunction (ETD) in a rat model. METHODS: Brown-Norway rats were sensitized to ovalbumin (OVA) and randomized to receive pre-treatment with IMO or phosphate buffered saline (PBS). After systemic sensitization, subjects received a transtympanic OVA challenge followed by evaluation of the Eustachian tube's dynamic function. RESULTS: Pre-treatment of OVA sensitized animals with IMO normalized passive opening and closing Eustachian tube pressures, improved active clearance of negative pressure in the middle ear, and resulted in reduced mean mucociliary transit times compared to untreated OVA-sensitized animals (P<0.001). CONCLUSION: These data demonstrate that pre-treatment with IMO prevent OVA-induced ETD in the rat. IMO treatment in the future may offer considerable promise in the management of OME in children.

Ototoxicity of cisplatin plus standard radiation therapy vs. accelerated radiation therapy in glioblastoma patients.

PURPOSE: To assess the effect of cisplatin (CDDP) plus concurrent radiation therapy on hearing loss. METHODS: 451 patients with glioblastoma multiforme (GBM) were randomly assigned after surgery to: Arm A: Carmustine (BCNU) + standard radiation therapy (SRT); Arm B: BCNU + accelerated radiation therapy (ART: 160 cGy twice daily for 15 days); Arm C: CDDP + BCNU + SRT; or Arm D: CDDP + BCNU + ART. Patients on arms C and D received audiograms at baseline, and prior to the start of RT, and prior to cycles 3 and 6. Otologic toxicities were recorded at each visit. RESULTS: 56% of patients had hearing loss at baseline. 13% and 50% of patients experienced worsening ototoxicity after 1 year of treatment in arms A and B vs. C and D, respectively, with 13% of those on arms C and D experiencing significant ototoxicity (>or= grade 3) at 6 months. Increasing age was associated with an increased risk of ototoxicity. CONCLUSIONS: Increased exposure to CDDP increases the risk of ototoxicity over time. Older patients are more susceptible to hearing loss with CDDP. The low proportion of patients with clinically significant ototoxicity suggests that baseline screening is unnecessary in GBM patients.

Effect of dantrolene on lipid peroxidation, lutathione and glutathione-dependent enzyme activities in experimental otitis media with effusion in guinea pigs.

The aims of our study were to assess whether the increased oxidative stress in experimental otitis media with effusion (OME) induced by histamine was reflected erythrocytes and middle ear effusion fluid by lipid peroxidation; to survey the alterations in antioxidant enzyme activities in experimental OME; and to determine the effect of dantrolene on this oxidative stress. Erythrocyte and middle ear effusion malondialdehyde (MDA) level, erythrocyte glutathione (GSH) and glutathione peroxidase (GSH-Px), glutathione reductase (GRD) and glutathione-S-transferase (GST) activities were measured in three groups of seven guinea pigs, 3 hours after injection of 0.1 mL of histamine (or saline) into the middle ear in guinea pigs with OME (experimental group), in a dantrolene sodium group and in a control group. Erythrocyte and effusion MDA levels in the dantrolene group were significantly lower than those of the experimental group. Erythrocyte GSH-Px, GST, GRD activities, and GSH levels were significantly higher in the dantrolene group than in the experimental group. Dantrolene sodium decreased the erythrocyte and effusion MDA levels, on the other hand, it increased the GSH and GSH-dependent enzymes. These findings suggest that reactive oxygen species (ROS) play a role in histamine-induced OME. Pre-treatment with dantrolene sodium increases antioxidant enzymes activities and decreases formation of MDA, the indicator of lipid peroxidation, in histamine-induced OME.

Expression of vascular endothelial growth factor receptors in experimental otitis media in the rat.

OBJECTIVE: Increased vascular permeability and endothelial cell growth are important in the pathogenesis of otitis media with effusion (OME) and vascular endothelial growth factor (VEGF) is known to play an important role in the increased vascular permeability and angiogenesis associated with OME. The action of VEGF is mediated by two different high-affinity receptors--VEGF receptor-1 (VEGFR-1; flm-like tyrosine kinase-1; flt-1) and VEGFR-2 (kinase insert domain-containing receptor; flk-1)--predominantly located on the vascular endothelium. The purpose of this study was to investigate the expression of three forms of VEGFR (-1, -2 and -3) in an endotoxin-induced rat model of OME. MATERIAL AND METHODS: Middle ear mucosa were obtained at 0, 1, 3, 6 and 12 h and 1, 3, 7 and 14 days after induction, and the expression of VEGFR mRNA and protein was evaluated using semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting. RESULTS: RT-PCR revealed that the expression of VEGFR-1 and -2 mRNA was upregulated between 1 h and 3 days after endotoxin instillation, with peak expression occurring at 12 h and on Day 1. No expression of VEGFR-3 mRNA was detected in any of the samples. Expression patterns of VEGFR-1 and -2 protein observed by Western blotting were similar to those of VEGFR-1 and -2 mRNA and peak expression was observed on Day 1. Expression of VEGFR mRNA or protein was not detected in either normal or saline-instilled middle ear mucosa. CONCLUSION: These results suggest that both VEGFR-1 and -2 are upregulated during experimental otitis media in the rat and these receptors may play different roles in the production of effusion in OME.