Pulmonary endothelial and alveolar epithelial lesions induced by O,O,S-trimethyl phosphorothioate in rats

Pulmonary effects of deltamethrin inhalation: an experimental study in rats

Deltamethrin is a synthetic pyrethroid widely used as the insecticide of choice especially for local vector mosquitoes in most countries. The application is mostly by cold aerosol spraying using vehicle-mounted equipment with a duration of 3-4 months during the summer. This experimental study aimed to evaluate the morphologic changes in the lungs caused by the inhalation of this insecticide. The study was performed on 30 mature male Wistar rats. While 10 of the rats were used as control group, 20 rats, separated into two groups, were exposed to 1:10 dilution of deltamethrin aerosol spray for 30 min each day for 45 days in doses of 6.0 and 12.0 mg/m3. The animals were sacrificed and tissue samples taken from the lungs were processed for both light microscopy and transmission electron microscopy. Light microscopic examination revealed heavy congestion, marked perivascular edema, and lymphoplasmocytic infiltration with focal nonspecific interstitial pneumonia, foamy macrophage accumulation, emphysema, peribronchial lymphoid tissue hyperplasia, and focal hemorrhage. Ultrastructurally, the ciliated cells of the airways appeared swollen with a few structurally abnormal cilia. Alveolar lining cells revealed mild degeneration and a slight hyperplasia in type II cells. Increases in the number of collagen bundles and edema in the alveolar septa were also noted.

Role of the lung in accumulation and metabolism of xenobiotic compounds--implications for chemically induced toxicity

The mammalian lung is exposed to and affected by many airborne and bloodborne foreign compounds. This review summarizes the role of lung in accumulation and metabolism of xenobiotics, some of which are spontaneously reactive or are metabolically activated to toxic intermediates. The specific architectural arrangement of mammalian lung favors that so-called pneumophilic drugs are filtered out of the blood and are retained within the tissue as shown in particular for amphetamine, chlorphentermine, amiodarone, imipramine, chlorpromazine, propranolol, local anaesthetics, and some miscellaneous therapeutics. There is strong evidence that intrapulmonary distribution activity and regulation of drug-metabolizing enzymes in lung is distinct from liver. This review focuses on the metabolic rate of selected compounds in lung such as 5-fluoro-2'-deoxyuridine, local anesthetics, nicotine, benzo(alpha)pyrene, ipomeanol, 4-methylnitrosamino-1-(3-pyridyl)-1-butanone. It is widely accepted that the formation of radical species is a key event in the pneumotoxic mechanisms induced by bleomycin, paraquat, 3-methylindole, butylhydroxytoluene, or nitrofurantoin. Finally, methodological approaches to assess the capacity of lung to eliminate foreign compounds as well as biochemical features of the pulmonary tissue are evaluated briefly.

Structure and pulmonary toxicity relationship on O,O-dimethyl S-alkyl phosphorothioate esters

The structure-pulmonary toxicity relationship was investigated using three different O,O,S-trimethylphosphorothioate (OOS-TMP) analogues, which is known to induce a typical mortality pattern (delayed death) and pulmonary injury; O,O-dimethyl S-ethyl (OOS-DMEP), O,O-dimethyl S-propyl (OOS-DMPP), and O,O-dimethyl S-butyl (OOS-DMBP) phosphorothioates. The mortality pattern in rats dosed with OOS-DMEP was similar to the "delayed death" pattern: the LD50s in rats for OOS-DMEP decreased dramatically from more than 200 mg/kg within 24 hr to 41.1 (males) or 13.8 (females) mg/kg 7 days after treatment while the LD50s in rats for OOS-DMPP and OOS-DMBP did not. Histopathological examinations revealed that OOS-DMEP induced pulmonary oedema and bleeding at a dose of 1/2 LD50 by 72 hr after dosing while the other two compounds did not. Thus, it was concluded that OOS-DMEP induces pulmonary injury, thereby eliciting the "delayed death" mortality pattern.

Long-term morphologic and biochemical changes induced by O,O,S-trimethyl phosphorothioate in the rat lung

The long-term pulmonary morphologic and biochemical changes induced by a single, sublethal dose of O,O,S-trimethyl phosphorothioate (OOS-TMP), an impurity present in organophosphorus insecticides, was examined in female WAG/Rij rats. Animals received either corn oil or a corn oil solution of OOS-TMP at a dose of 40 mg/kg body weight by gavage and were studied at the following time intervals after treatment: 10 days, 30 days, 90 days, 6 months, and 1 year. No control or OOS-TMP-treated animal died spontaneously. Significant increases in wet and dry lung weights occurred at all times examined in OOS-TMP-treated rats compared to those in age-matched controls. No difference was observed in percentage lung water content between treated and control rats. OOS-TMP treatment resulted in hypertrophy and hyperplasia of type II alveolar epithelial cells having morphologic alterations in the size and number of osmiophilic lamellar bodies. Interstitial changes were characterized as increased numbers of fibroblasts accompanied by increased amounts of collagen fibrils and basement membrane alterations. There was also a significant increase in pulmonary hydroxyproline content in OOS-TMP-treated animals compared to that in controls at all time periods. Collagen deposition was predominantly associated with the interalveolar septa rather than being oriented around airways. The results of this study indicate that a single, sublethal dose of OOS-TMP induces long-term structural and biochemical changes in the rat lung.

Morphogenesis of O,O,S-trimethyl phosphorothioate-induced pulmonary injury in mice

The purpose of this study was to establish and characterize an experimental model in mice that examined the pulmonary effects of O,O,S-trimethyl phosphorothioate (OOS-TMP), a contaminant present in commercially important organophosphorus insecticides. Characterization of the model will allow the delineation of comparative effects between species and its possible extrapolation to man, and provide an additional experimental animal species satisfactory for mechanistic-oriented studies on OOS-TMP and related compounds. The morphogenesis of pulmonary injury induced by OOS-TMP was studied in mice by light and transmission electron microscopy. Weanling female C57BL/Ka mice received OOS-TMP dissolved in corn oil by intraperitoneal injection and were studied at intervals from 6 to 168 hr after treatment. Morphologic changes were observed in Clara cells only at the initial time period examined. Injury of pulmonary parenchymal cell populations, including the endothelium and type I alveolar epithelium, occurred after morphologic changes indicative of severe cell injury and necrosis in Clara cells. Endothelial cell injury was accompanied by significant increases in wet lung weight and percentage lung water content. Type I alveolar epithelial cell injury and loss resulted in a bare basal lamina, followed by attenuation, hypertrophy, and hyperplasia of type II alveolar epithelial cells. The results of this study document the successful establishment of a mouse experimental model of OOS-TMP-induced pulmonary toxicity. It is concluded that the Clara cell was the initial and most severely affected pulmonary cell population in mice receiving OOS-TMP. The administration of OOS-TMP in mice also results in marked morphologic alterations in the pulmonary parenchyma that were accompanied by significant changes in lung weight and composition.