Early and delayed biochemical effects of paraquat toxicity on rat lung

Metabolic changes in the mouse kidney after subcutaneous injection of butyl 2-chloroethyl sulfide

Subcutaneous exposure to vesicants such as butyl 2-chloroethyl sulfide (butyl mustard, BCS) produces local tissue injury (vesication) primarily by alkylation and cross-linking of the purine nucleotides and rapidly binding to proteins. We recently reported that administering BCS can cause other biochemical and morphological alterations, not only in tissues at the injection site but in other areas as well. In this study, we have examined the metabolic effects of BCS administration on the mouse kidney. At 1, 24, and 48 h after injection (5 microliters neat, sc), treated mice were terminated along with an untreated control group, and the kidneys were analyzed for metabolic changes. Glutathione (GSH) peroxidase (GPx) activity markedly increased, (+78 and +85%), but NADP-dependent isocitrate dehydrogenase activity decreased (-43 and -37%) at 1 and 24 h, respectively. Glucose-6-phosphate dehydrogenase (G6PD) remained unchanged at 1 and 24 h, but increased 20% (p less than .05) at 48 h after injection. Kidney glutathione S-transferase (GST) was increased at 24 h after injection. Both total and oxidized GSH levels were significantly lower than control values (approximately 30%) at all time points. Lipid peroxidation, as estimated by the thiobarbituric (TBA) acid-reactive products, was 45% lower (p less than .05) after 1 h. Kidney GPx, G6PD, and GT activities and kidney GSH levels were consistent with changes associated with oxidative stress or detoxication mechanism for BCS. The decrease in TBA-reactive products suggests that mouse kidney metabolic response to BCS injection was different from responses observed for other organs (eyes, brain, and lung).

Cellular response to oxidative damage in lung induced by the administration of dimethylarsinic acid, a major metabolite of inorganic arsenics, in mice

Oral administration of dimethylarsinic acid (DMAA), a major metabolite of inorganic arsenics, induces DNA damage in the mouse and rat lung due to both active oxygens and dimethylarsenic peroxyl radical produced in the metabolism of DMAA. Our paper describes the cellular response to DMAA in the mouse lung. In male ICR mice given a single po dose (1500 mg/kg) of DMAA-Na, the activities of mitochondrial superoxide dismutase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase significantly increased at 6 hr or longer after dosing, while cytosolic superoxide dismutase and catalase did not. With regard to cellular sulfhydryls after DMAA dosing, levels of reduced glutathione and nonprotein sulfhydryl decreased, while mixed disulfides significantly increased. Further, NADPH markedly decreased at 6-9 hr after DMAA dosing. These cellular variations suggest that the mouse pulmonary cell produced active oxygens, i.e., superoxide anion radical, hydrogen peroxide, and subsequent radicals in the metabolism of DMAA and that these and also the dimethylarsenic peroxyl radical were responsible for pulmonary DNA damage.

Prolonged, intravenous paraquat infusion in the rat. I. Failure of coinfused putrescine to attenuate pulmonary paraquat uptake, paraquat-induced biochemical changes, or lung injury

Paraquat (PQ) was administered to rats for 7 days by iv infusion from osmotic minipump at dosage rates of 250 and 500 nmol PQ/hr. The efficacy of putrescine in attenuating pulmonary PQ accumulation in vivo and the resulting PQ-induced biochemical changes and lung injury were assessed in these animals by coinfusion of putrescine at rates of 2500 or 5000 nmol/hr. Dose-dependent, steady-state blood levels of both PQ and putrescine were achieved by 18 hr and maintained throughout the infusion period. Lung PQ content at 7 days was dose-dependent and up to 18-fold greater than corresponding blood levels. No evidence of toxicity was observed in low-dose PQ animals while weight loss and overt toxicity was observed in high-dose PQ rats between Days 4 and 5. Histopathological examination of high-dose PQ rat lungs revealed qualitative changes typical of PQ toxicity. Significant (p less than 0.05) increases in lung glutathione and activities of glucose-6-phosphate dehydrogenase and GSSG reductase resulted from both PQ doses, reflecting PQ-induced oxidant stress and increased demand on lung NADPH. A net decrease in lung NADPH (p less than 0.05) was directly measured in high-dose PQ rats and may have contributed to the PQ-induced lung injury. Although putrescine is an effective inhibitor of pulmonary PQ uptake in vitro, the blood putrescine levels achieved in this study did not appear to inhibit this process in vivo. This was evidenced by putrescine's failure to decrease 7-day lung PQ content, PQ-induced biochemical changes, or lung injury.

Lung hydrolases in paraquat poisoning: early response of alkaline phosphatase

In order to evaluate the early response of the alveolar epithelium following lung injury, male Long-Evans adult rats (280-350 g) were treated with a single dose (30 mg/kg, ip) of the herbicide paraquat. No animal died during the 72 h that followed the acute administration of the herbicide. When compared to control, total lipid, phosphatidylcholine, and disaturated phosphatidylcholine contents of lung homogenates from the paraquat-treated rats were significantly reduced 48 h postdose (respectively 10, 24, and 37%). Comparatively, the total lung alkaline phosphatase activity was significantly reduced as early as 12 h postdose, and by 48 h the activity had decreased by approximately 50%. Although a significant decrease in total lung acid phosphatase activity was observed 24 and 48 h after the treatment, the effect was much less than with the alkaline phosphatase activity (15% versus 50%, respectively). The lysosomal beta-N-acetylglucosaminidase and the cytoplasmic lactate dehydrogenase activities were not affected by the herbicide treatment. A subcellular fractionation of the treated lungs showed that 48 h postdose, the total alkaline phosphatase activities associated with lamellar body and surfactant fractions were decreased respectively by 60% and 49%. Due to the intrinsic association of a strong alkaline phosphatase activity with the pulmonary surfactant system, these data suggest that the monitoring of the alkaline phosphatase activity in lung fractions could represent an early and sensitive indicator of toxicity to the alveolar epithelium, most probably to type II cells.

Selected pulmonary biochemical and hematological changes produced by prolonged hypoxia in the rat

Rats were exposed to 12% O2 (1 atm) for 48 hr, then 10% O2 for the duration of the exposures. Significant elevations in enzymes of the glutathione peroxidase system were found in the lungs of rats killed 3.5, 7.5, and 12.5 days of exposure compared to air-breathing controls. Superoxide dismutase was also elevated after hypoxia but nonsignificantly. Animals killed 12.5 days after exposures exhibited 75% (P less than 0.05) more thiobarbituric acid reactive products in their lungs compared to controls. These results along with significant increases of lung lipid peroxidation and in an augmentation of protective antiperoxidative lung defense capabilities. Hypoxia also resulted in enzyme elevations of lung phosphofructokinase and pyruvate kinase, which may indicate an adaptive increase in lung glycolytic capabilities which would be helpful in maintaining lung tissue energy requirements during hypoxia. In addition, it was confirmed that red blood cell count, hemoglobin and hematocrit values increased after prolonged hypoxia. The results of this study might also reflect enzyme elevation/induction due to cellular reparative-proliferative processes following hypoxia.

A new model of diffuse interstitial pulmonary fibrosis in the rat

We have produced experimental diffuse interstitial pulmonary fibrosis in rats with a combination of low and repeated doses of paraquat plus continuous exposure to normobaric 74% O2 in the breathing air for several weeks. Pulmonary fibrosis was evaluated histologically and biochemically, through the determination of total collagen content in the lung. Our procedure is characterized by low initial mortality, the development of extensive distortion of the pulmonary architecture, and the presence of severe and diffuse interstitial fibrosis. The model was compared with bleomycin-induced pulmonary fibrosis in the same rat strain, in which the process is focal and leaves most of the lung unaffected. We conclude that lung damage produced by the combination of low doses of paraquat plus normobaric 74% O2 concentration in the breathing air is an adequate experimental model of diffuse interstitial pulmonary fibrosis as it occurs in many of the human cases of this condition.

Alteration of alveolar surfactant function after exposure to oxidative stress and to oxygenated and native arachidonic acid in vitro

Alveolar surfactant is known to be impaired after inhalation of various oxidizing agents (NO2, ozone) as well as in inflammatory lung processes, in which leucocyte-derived active oxygen species or arachidonic acid oxygenation products may be involved. The effect of lipid peroxidation, oxygen-free radicals and oxygenated versus native arachidonic acid on the surface tension behaviour of natural surfactant was tested in vitro. The studies were performed on pooled surfactant material, obtained from bronchoalveolar lavage of rabbit lungs, in a Langmuir trough/Wilhelmy balance system. Initiation of lipid peroxidation with FeCl3/ascorbate or UV radiation and the generation of OH.(FeCl2/EDTA/H2O2), O2-. (xanthine/xanthine oxidase) and 1O2 (NaOCl/H2O2) provoked a common profile of changes: delayed reduction of surface tension during compression with an increase in minimal compressibility accelerated decrease of film pressure during expansion, reduction of hysteresis area and markedly augmented monolayer collapse rate. Addition of arachidonic acid resulted in decreased minimal compressibility, stability index and hysteresis area. Incubation with the arachidonic acid cyclooxygenase products, prostaglandin E2, I2, F2 alpha or thromboxane B2, with soybean lipoxygenase or with H2O2 and O2-exposure caused only moderate or no alteration of surfactant behaviour in vitro.

CONCLUSION

oxidative stress, but not arachidonic acid oxygenation products, provoked altered surface tension behaviour of natural surfactant in vitro.