32P-Postlabeling of a DNA adduct derived from 4,4′-methylenedianiline, in the olfactory epithelium of rats exposed by inhalation to 4,4′-methylenediphenyl diisocyanate

Tissues obtained from female Wistar rats exposed to a 0.9 μm aerosol of 4,4′-methylenediphenyl diisocyanate (MDI) for 17 h per day, 5 days per week, for one year, at levels of 0, 0.3, 0.7 and 2.0 mg/m3, were analyzed for DNA adducts. A 32P-postlabeling method was used to detect (i). adducts formed by the reaction of the isocyanate group(s) of MDI with DNA; and a 32P-postlabeling method was adapted to detect (ii), a DNA adduct formed by 4,4′-methylenedianiline (MDA), a hydrolysis/decarboxylation product of MDI. In the lung, neither isocyanate adducts nor the arylamine adduct were detectable. The same negative result was seen in the liver, the bladder, the kidney, the respiratory epithelium and in peripheral lymphocytes. In the olfactory epithelium, on the other hand, the aryl-amine-derived DNA adduct was detected, at the very low levels of 5, 9 and 10 adduct-nucleotides per 1010 nucleotides, for the three dose groups, respectively. The adduct co-chromatographed with the one formed in the liver of rats after oral gavage of MDA. The results are discussed in terms of the importance of genotoxic versus nongenotoxic aspects of carcinogenesi

32P-Postlabeling of a DNA adduct derived from 4,4′-methylenedianiline, in the olfactory epithelium of rats exposed by inhalation to 4,4′-methylenediphenyl diisocyanate

Tissues obtained from female Wistar rats exposed to a 0.9 μm aerosol of 4,4′-methylenediphenyl diisocyanate (MDI) for 17 h per day, 5 days per week, for one year, at levels of 0, 0.3, 0.7 and 2.0 mg/m3, were analyzed for DNA adducts. A 32P-postlabeling method was used to detect (i). adducts formed by the reaction of the isocyanate group(s) of MDI with DNA; and a 32P-postlabeling method was adapted to detect (ii), a DNA adduct formed by 4,4′-methylenedianiline (MDA), a hydrolysis/decarboxylation product of MDI. In the lung, neither isocyanate adducts nor the arylamine adduct were detectable. The same negative result was seen in the liver, the bladder, the kidney, the respiratory epithelium and in peripheral lymphocytes. In the olfactory epithelium, on the other hand, the aryl-amine-derived DNA adduct was detected, at the very low levels of 5, 9 and 10 adduct-nucleotides per 1010 nucleotides, for the three dose groups, respectively. The adduct co-chromatographed with the one formed in the liver of rats after oral gavage of MDA. The results are discussed in terms of the importance of genotoxic versus nongenotoxic aspects of carcinogenesi

Aerosolized surfactant inhibits acetylcholine-induced bronchoconstruction in rats

Pulmonary surfactant is important for the stability of the alveoli and the small airways and has been shown to modulate the function of respiratory inflammatory cells and macrophages. Intratracheal pretreatment with surfactant is cabable of inhibiting the antigen-induced bronchoconstriction in sensitized guinea pigs (Becher, Biomed. Biochim. Acta 44, 1985) In addition, nebulized surfactant was shown to improve respiratory function in asthmatic patients ( Kurashima et al., Jpn. J. Allergol. 40, 1991). The aim of this study was to investigate the effect of aerosolized surfactant on receptor-mediated bronchoconstriction in comparison to inhaled terbuline in rats. Anaesthetized intubated spontaneously breathing Wistar-rats (350-450 g) were either pretreated with aerosolized vehicle ( Ringer's solution, "control", n=9), terbutaline (0,027% w/v, "terbutaline*1", n=8 and 0,054% w/v, "terbutaline*2", n=5) or surfactant ( Alveofact®, "alveofact", n=8), respectively using a jet nebulizer for eff icent aerosol generation (Bronchy-H, Fraunhofer Institute).Animals were then challenged by aerosolized acetylcholine (ACh) in a standardized computer-controlled manner to elicit receptor-mediated bronchoconstriction. Aerosol concentration was monitored continuously by photometer. Particle size distribution was determined for all aerosols to estimate the amount of aerosol deposited in the lungs. Spontaneous respiratory function parameters were measured using whole-bodyplethysmography. The following parameters were calculated and recorded before pretreatment and prior and after the ACh-challenge: airway resistance (Raw), compliance (C), tidal volume (Vt), minute volume (MV) and breathing frequency (f). There was no significant difference in baseline values prior and after pretreatment between the treatment groups. ACh-challenge induced a significant bronchoconstriction with an increase of Raw in control of 64,0+-7,7% (mean +- SEM), whereas the increase of Raw in terbutaline*1, terbutali n e*2 and alveofact was 45,2+-8,4%, 36,0+- 6,8% and 34,4+-4,9%, respectively. For terbutaline*2 and alveofact this difference was significant compared to control (P<0,05, ANOVA followed by t-test). The other spontaneous respiratory function parameters were not significantly different between the treatment groups. In conclusion, both alveofact and terbutaline reduce the ACh-induced bronchoconstriction in rats. Further studies are needed to investigate the underlying mechanisms of the surfactant effect. Alveofact was a generous gift by Dr. K. Thomae GmbH, Biberach, Germany

Pulmonary lesions in Wistar rats associated with chronic inhalation of 4,4'-methylene-diphenyl-diisocyanate (MDI)

Isocyanates are important primary material at the production of polyurethane plastics, varnishes and glues. Nearly 3 million tons of isocyanate are produced yearly worldwide.Isocyanate have a irritating effect on eyes and airways as well as a sensitizing effect on the respiratory tract (isocyanate asthma). Since the risks for human health resulted mainly from inhalation uptake, a long-term inhalation toxicity/carcinogenicity study sponsored by the Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit/Umweltbundesamt (FKZ 11606084) was performed. 320 female Wistar rats (Crl:[WI]BR) were allocated to 4 groups of 80 females each and exposed in 6 m³ whole body inhalation chambers on average 17 h/day, 5 day/week for upto 24 months to clean air or to 0.2, 0.7 and 2.1 mg/m³ of monomeric MDI (MMAD: 1.03-1.06) aerosol. In the following, the main histopathological findings of the carcinogenicity study are summarized with emphasis on the lungs