Toxic effect of 2,3,7,8,-tetrachlorodibenzo-p-dioxin [TCDD] on the lungs' alveolar epithelium of rats and the protective effect of vitamine E. a histological study

ABSTRACT

2, 3, 7, 8,-Tetrachlorodibenzo-p-dioxin [TCDD] has been classified as a known human carcinogen, and the epidemiologic studies identi5 the lung as one of the target organs. Few experimental studies have attempted to characterize pulmonary effects of TCDD exposure. Objective: Based on the theory of dioxin as a cause of oxidative stress, this work was designed to study the effect of chronic exposure to 2, 3, 7, 8,-Tetrachlorodibenzo-p-dioxin [TCDD] on the alveolar epithelium of rats and the use of the antioxidant; vitamin F to ameliorate this effect. Methods: Male Sprague Dawely rats were administered TCDD at a daily dose of 125 ng/kg body weight for 16 weeks. Another group of animals were co-administered TCDD [125 ng/kg body weight] and vitamin E in a daily dose of2Q mg/kg body weight for 16 weeks. Results: Administration of TCDD alone showed alteration in the lungs' alveolar architecture with marked thickening of the interalveolar septa, edema, cellular infiltration both peribronchiolar and perivascular together with vascular congestion and interstitial hemorrhage. Type II pneumocyte cells formed the predominant lining cells of the alveoli. Co-administration of TCDD and vitamin F showed considerable degree of preservation of the lung alveolar architecture. Most of the alveoli were patent lined with the two types of pneumocytes with type I predominance. Conclusion: The results established that prolonged gavage administration of TCDD to male Sprague Dawely rats can induce lung lesions, both proliferative and degenerative. In this work TCDD were unable to induce neoplastic changes, suggesting that additional factors are necessary for tumor induction. Alpha-tocopherol [vitamin F] effectively protected lung tissues against dioxin toxicity and this was attributed to its antioxidant properties