Morphological alterations of rat lung bronchiolar epithelium produced by various trialkyl phosphorothioates

A pneumotoxin, O,O,S-trimethyl phosphorothioate, induces hemorheological alteration in rats

O,O,S-trimethyl phosphorothioate (OOS-TMP), an impurity present in widely used organophosphorus insecticides, has been shown to induce lung injury after oral administration. To date, very little is known about the hemorheological changes which may occur during the inflammation of lung caused by OOS-TMP. The present study has demonstrated that oral administration of OOS-TMP (10 mg/kg, 20 mg/kg) to rats produced an increase in whole blood apparent viscosity at 24, 48 and 72 h following the treatment in rats. Concomitantly, the plasma fibrinogen level and red blood cell (RBC) aggregation were increased at 24 and 48 h. There was no change in RBC filterability. Thus, OOS-TMP, a pneumotoxin, was capable of causing a systemic hemorheological alteration, probably via increase in fibrinogen content, an acute-phase protein, in rats.

O,S,S,-trimethyl phosphorodithioate-induced lung damage in rats and mice

O,S,S,-Trimethyl phosphorodithioate (OSS) is a contaminant of various organophosphorus insecticides which induces delayed damage to rat lung bronchiolar and alveolar epithelial cells. Whether lung damage occurs in mice has not been tested. Changes in DNA synthesis, an index of cell division after the induction of damage, were monitored by measuring thymidine incorporation into pulmonary DNA. Mice, treated with 45 mg/kg OSS, exhibited a significant increase in pulmonary thymidine incorporation on Day 5. Maximal increases occurred on Days 7-10 and were followed by a gradual decline to control levels by Day 15. The labeling index of mouse lung cells, determined following autoradiography, exhibited a similar time course. Differential cell counts indicated that maximal division of type II cells occurred before that of interstitial cells, although interstitial cells were the predominant type labeled at all times. Pulmonary DNA synthesis was significantly increased in rats 2 days after treatment with 90 mg/kg OSS. Maximal thymidine incorporation was measured on Day 3, followed by a decline to control levels on Day 5. Thymidine incorporation into total lung DNA was dose related in both species. Maximal increases appeared after 45 and 90 mg/kg OSS in mice and rats, respectively. The histopathological changes in mouse lung tissue were similar, but somewhat less severe than those seen in rats. Rats exhibited a severe interstitial pneumonitis with type I alveolar cell destruction followed by type II cell proliferation. Mice exhibited a mild to moderate alveolitis with only slight damage to type I cells. Necrosis of bronchiolar Clara cells was evident in both species but was more extensive in rats. SKF 525a and piperonyl butoxide prevented OSS-induced increases in pulmonary DNA synthesis in rat lung suggesting that metabolic activation was necessary to elicit damage. Piperonyl butoxide treatments had no effect, however, on thymidine incorporation after OSS in mouse lung tissue, and the highest dose of SKF 525a had only a moderate inhibitory effect on this parameter while increasing animal mortality. These data indicate that systemic treatment with OSS results in damage to mouse, as well as rat, lung tissue at both the alveolar and bronchiolar levels.

Alterations of alveolar macrophage function and level of bronchopulmonary protease inhibitors in O,O,S-trimethyl phosphorothioate-induced lung injury

O,O,S-Trimethyl phosphorothioate (OOS-TMP), an impurity present in widely used organophosphorus insecticides, has been shown to induce pneumotoxicity after oral administration. To date very little is known about the pathogenesis of the injury. Protease-anti-protease imbalance has been proposed as a mechanism of various lung injuries; thus, the effect of OOS-TMP on alpha 1-protease inhibitor capacity, pulmonary alveolar macrophage (PAM) esterases, cytotoxic activity and on specific esterase inhibitors in the bronchopulmonary lavage fluid and serum were measured. OOS-TMP (20 mg/kg) administered orally to rats produced a 27% increase in PAM esterase activity 6 h after treatment. The activity then declined to 63% of control value on day 3 and had not recovered to any significant extent on day 7. The cytotoxic activity of PAM was significantly increased at 6 h and 24 h following treatment. Chymotrypsin inhibitory capacity (CIC) of the lavage fluid was decreased by 45% at 6 h but recovered rapidly and reached control levels by 24 h. Trypsin inhibitory capacity (TIC) of serum was affected to a lesser extent such that no change was detected after 6, 12 or 24 h. These data, early elevation of PAM esterase levels with a concomitant increase in cytotoxic activity and decreased TIC and CIC in bronchopulmonary lavage fluid, support the view that pathogenesis of OOS-TMP produced lung injury could be due to increased protease levels.

Systematically applied chemicals that damage lung tissue

A large, and increasing number of drugs and chemicals have been found which are toxic to lung following systemic administration. These agents damage lung tissue specifically, or in addition to damage to other tissues. Mechanisms explaining the pulmonary damage produced by some lung toxins have been uncovered. These include concentration of the agent within lung, the absence of adequate pulmonary detoxication systems, and bioactivation to a toxic species within specific lung cells or at distant sites followed by transport to the lung. The basic biochemical lesions underlying lung damage, responses of individual lung cells and pulmonary repair processes to the toxic agent, and species and age differences in susceptibility to lung damage have not, however, been well defined for most lung toxins. This review describes the information available on pulmonary biochemical and pathological changes associated with some of these lung-toxic agents. In addition, mechanisms proposed to explain the lung damage are discussed. The agents covered include: paraquat, the thioureas, butylated hydroxytoluene, the trialkylphosphorothioates, various lung-toxic furans and antineoplastic agents, the pyrrolizidine alkaloids, metals and organometallic compounds, amphiphilic agents, hydrocarbons, oleic acid, 3-methylindole, and diabetogenic agents. Detailed reviews on the overall toxicity of many of these agents have been published elsewhere. This review concentrates on their pulmonary toxicity. Information is presented as an overview to illustrate both the extensive literature that is available and the important questions that remain to be answered about systemic chemicals that damage lung tissue.

Interaction of O,O,S-trimethyl phosphorothioate and O,S,S-trimethyl phosphorodithioate, the impurities of malathion with supercoiled PM2 DNA

The interaction of O,O,S-trimethyl phosphorothioate and O,S,S-trimethyl phosphorodithioate, the impurities found in malathion, with DNA at pH 8.0, was investigated. Supercoiled PM2 DNA was incubated with these compounds at pH 8.0 at 37 degrees C and then the superhelicity of the modified DNA was determined by gel electrophoresis. Both compounds caused unwinding of supercoiled DNA in dose- and incubation time-dependent manner. O,S,S-trimethyl phosphorodithioate was a more potent agent than O,O,S-trimethyl phosphorothioate. At 37 degrees C following 2.0 hours incubation, 100 mM O,S,S-trimethyl phosphorodithioate produced fully unwound DNA, whereas at 200 mM O,O,S-trimethyl phosphorothioate produced 80% unwound DNA following 12 hours' incubation. At the same condition, 5 mM methyl methanesulfonate, a potent alkylating mutagen, produced fully unwound DNA following 1 hour incubation at 5 mM. These results indicated that there were chemical interactions between these agents and DNA. The possibility of the interaction of OOS-TMP being as a covalent intercalation as well as strand nicking was discussed.