Enhanced lung toxicity of paraquat in selenium-deficient rats

In an attempt to further clarify the mechanisms of paraquat lung injury, paraquat toxicity was studied in selenium (Se)-deficient rats. Chronic respiratory disease-free rats fed a basal Se-deficient diet or a basal diet supplemented with 0.5 or 2.0 ppm of Se for 40 days after weaning were injected with 25 mg/kg of paraquat dichloride (ip). Within 4 hr after paraquat injection, 50% of the rats fed the Sedeficient regimen died, exhibiting neurological and respiratory signs of distress prior to death, whereas all rats fed Se-supplemented diets survived for this short time span. Excised lungs from surviving Se-deficient rats injected with paraquat showed extensive lung damage, as evidenced by gross examination, increased lung weights, and increases in cystosolic lung lysosomal enzymes, and exhibited a significant increase of thiobarbituric acid (TBA)-reactive products. Excised lungs from Se-supplemented rats failed to show similar increases in these indices of paraquat-induced lung injury. Our data confirms and extends previous findings of others that paraquat toxicity is enhanced in Se-deficient animals and suggests that lipid peroxide formations may play a role in the enhanced susceptibility.     

Biochemical effects of intratracheal instillation of cadmium chloride on rat lung.

Selected biochemical parameters in rat lung tissue were examined after intratracheal instillation of 0.5 μmole/kg of cadmium chloride (CdCl₂), which produces levels of approximately 10 μg Cd/g of lung wet weight 1 hr following instillation. Lungs were examined 2 hr, 1 day, 3 days and 7 days after CdCl₂ instillation and compared with matched controls receiving saline instillations. Cytosolic lysosomal enzymes, Superoxide dismutase (SOD), catalase, and glutathione (GSH) peroxidase-associated enzymes increased significantly 24 hr after CdCl₂ insult. Peak increases of enzyme activities occurred about 3 days after CdCl₂ instillation. Levels of lung nonprotein sulfhydryl (NPSH) groups, thiobarbituric acid (TBA)-reactive products, protein and DNA increased after CdCl₂ instillation in a similar manner. By 7 days most measured biochemical parameters either remained at the peak 3-day values or decreased toward normal levels. The biochemical changes are consistent with known reported CdCl₂-induced edema and inflammation accompanied by phagocyte recruitment into lung tissue and reparative proliferation of lung cell types.     

Dietary antioxidants and the biochemical response to oxidant inhalation: I. Influence of dietary vitamin E on the biochemical effects of nitrogen dioxide exposure in rat lung

Sprague-Dawley rats derived from a specific pathogen-free colony were raised from birth on a test diet containing either 0 or 50 IU vitamin E/kg diet for 8 weeks. Rats from each dietary group were exposed to 3 ppm (5640 μg/m³) nitrogen dioxide (NO₂) continuously for 7 days. They were then killed, and the lungs analyzed for changes in weight, DNA and protein contents, tissue oxygen utilization, sulfhydryl metabolism, and the activities of NADP-reducing enzymes. The difference in dietary vitamin E alone did not cause any significant changes in these parameters. However, after NO₂ exposure the changes in these parameters relative to their corresponding unexposed controls were greater for the deficient rats than for the supplemented rats. The biochemical changes observed may be a response of the lung to injury from NO₂ exposure. The larger changes in the lungs of deficient rats may reflect a greater sensitivity of these animals to inhaled NO₂. The vitamin E contents of lung tissue in deficient and supplemented rats reflected the dietary levels. After NO₂ exposure, the vitamin E content in the lung increased significantly in supplemented rats but decreased in the deficient rats relative to their corresponding unexposed controls. The elevation of vitamin E levels in the lungs of supplemented rats with NO₂ exposure suggests its mobilization from other body sites, whereas in deficient rats this process may not have been possible.     

Metallothionein Induction and Pulmonary Responses to Inhaled Cadmium Chloride in Rats and Mice

Inhaled CdCl₂ is a pulmonary carcinogen in rats but not in mice.We hypothesized that pulmonary metallothionein (MT) inductionmay be different in both species and thereby may lead to differentlevels of protection from Cd-induced lung injury. Fisher-344rats and B6C3F₁ mice were exposed for 4 weeks to CdCl₂ aerosolsof 0, 30, 50, and 150 µg/m³ air or 0, 10, 30, and 100µg/m³ air, respectively. Animals from each exposure groupwere terminated at 1, 30, and 133 days after the end of exposure.The lungs were lavaged for cell and biochemical analyses. Cadmiumand MT in lavagate and lung tissue were measured. The retentionhall-time of pulmonary Cd was greater in mice (290 vs 90 days,p<0.05). Cd exposure provoked an inflammatory response whichwas dose-dependent in both species, and while it was only short-livedin rats, it persisted throughout the observation period in miceat the high exposure concentrations. Mice were found to havea greater baseline level of MT (18.046.96 vs 11.71.98 µgMT/g control lung, p<0.05). Mice showed greater inducibilityof MT for a given CdCl₂ exposure concentration; however, bothspecies had a similar relationship between retained pulmonaryCd and MT induction though mice maintained increased MT levelsfor a longer period of time. The greater pulmonary baselineMT together with the longer presence of Cd-induced pulmonaryMT may result in greater protection from Cd carcinogenicityin spite of the greater pulmonary Cd-induced inflammation inmice.     

Subacute oral toxicity of trisodium nitrilotriacetate (Na3NTA) in dogs

Trisodium nitrilotriacetate was fed to dogs for 90 days at 0.03, 0.15 and 0.5% of the diet. No test-related changes were observed in general appearance, survival, hematology, serum chemistry, urinalysis or microscopic tissue examination. No significant changes were observed between control and test groups in fecal cation excretion. There was a significantly greater increase in urinary zinc excretion from dogs in the mid- and high-dose groups. The increase in zinc excretion did not produce a zinc deficiency as measured by pathological and biochemical techniques. NTA was deposited in bone (123–142 ppm at the 0.5% level), but this was without adverse effect. It is concluded that Na₃NTA at the 0.5% level in the diet of dogs for 90 days does not produce a toxic response.     

Early damage indicators in the lung. III. Biochemical and cytological response of the lung to inhaled metals salts.

The validity of using the enzymatic and cytologic profile of airway fluids to indicate lung damage was tested in animals exposed by inhalation to either a known toxic metallic salt (CdCl₂) or a relatively innocuous salt (CrCl₃). The enzymatic and cytologic response of the airways was compared to histopathological evaluation of lung damage. Syrian hamsters were exposed to an aerosol of CdCl₂ (aerodynamic diameter = 1.7 μm, $\text{σ}{}_{\mathrm{g}}\text{? 1.7}$) to achieve an initial lung burden (ILB) of 0.6 ± 0.3 and 4.4 ± 1.2 μg of CdCl₂ or to an aerosol of CrCl₃ (count median diameter = 1.2 μm, $\text{σ}{}_{\mathrm{g}}\text{? 1.5}$) to achieve an ILB of 0.7 ± 0.2 or 20 ± 10 μg of CrCl₃. Animals were sacrificed at 2 hr, 1, 7, and 21 days after exposure. A sample of airay fluid was obtained by bronchopulmonary lavage and examined for the enzymatic profile of the cell-free fraction and the cytological profile of the cell fraction. Lung tissue enzyme activities were also measured and histopathologic evaluations were made on lung tissue from exposed, but nonlavaged, animals. In the lavage fluid from animals exposed to CdCl₂, the enzymatic and cytologic data demonstrated a dose-response pattern and the airway response preceded enzymatic changes in the lung tissue. Tissue morphological changes correlated well with the biochemical changes. The response of the lung to CrCl₃ was minimal by both morphological and biochemical evaluations. Airway enzymatic and cytologic responses were shown to be potentially useful as indicators of lung damage in toxicological screening programs.     

Effects of subchronic cadmium poisoning on DNA methylation in hens

Cadmium is a persistent pollutant that poses a threat to most biological organisms including birds. Although toxicity of cadmium is mainly linked to cancer, the mechanism of its carcinogenic activity remains poorly understood. Since DNA methylation is linked to cancer, we have examined the effect of cadmium on DNA methylation and DNMTs mRNA expression in hen liver and kidney. Sixty 50-day-old hyline-white hens were randomly allocated into 3 equal groups; a control group fed a basal diet, a low-dose group fed the basal diet spiked with 140 mg/kg CdCl₂, and a high-dose group fed the basal diet spiked with 210 mg/kg CdCl₂. After 60 days, liver and kidney samples were analysed for cadmium by FAAS, DNA methylation level by HPLC and DNMTs mRNA levels by semi-quantitative RT-PCR. The DNA methylation levels and the expressions of DNMT1 and DNMT3a mRNA in liver and kidney were significantly elevated by the cadmium treatment but there was no change in the expression of DNMT3b mRNA in the two tissues. The fact that cadmium increases DNA methylation and the expressions of DNMT1 and DNMT3a mRNA in liver and kidney suggests DNA methylation may be involved in the carcinogenic action of cadmium.     

Dietary iron lowers the intestinal uptake of cadmium-metallothionein in rats

It has been shown that addition of extra calcium/phosphorus (Ca/P), zinc (Zn) and iron (Fe²⁺) to the diet results in a significant protection against cadmium (Cd) accumulation and toxicity in rats fed inorganic Cd salt. However, it is not clear whether the presence of these miniral supplements in the diet also protects against the Cd uptake from cadmium-metallothionein. The present study examines the influence of Ca/P, Zn and Fe²⁺ on the Cd disposition in rats fed diets containing either 1.5 and 8 mg Cd/kg diet as cadmium-metallothionein (CdMt) or as cadmium chloride (CdCl₂) for 4 weeks. The feeding of Cd resulted in a dose-dependent increase of Cd in intestine, liver and kidneys. The total Cd uptake in liver and kidneys after exposure to CdMt was lower than after exposure to CdCl₂. At the low dietary Cd level and after addition of the mineral supplement, the kidney/liver concentration ratio increased. However, this ratio was always higher with CdMt than with CdCl₂, suggesting a selective renal disposition of dietary CdMt. The uptake of Cd from CdCl₂ as well as from CdMt was significantly decreased by the presence of a combined mineral supplement of Ca/P, Zn and Fe²⁺. The protection which could be achieved was 72 and 75% for CdMt and 85 and 92% for CdCl₂ after doses of 1.5 mg/kg and 8 mg/kg respectively. In a following experiment it was shown that the protective effect of the mineral mixture against CdMt was mainly due to the presence of Fe²⁺. It seems clear that Cd speciation and the mineral status of the diet have a considerable impact on the extent of Cd uptake in rats.     

The induced synthesis of metallothionein in various tissues of rats in response to metals. II. Influence of zinc status and specific effect on pancreatic metallothionein

Metallothionein (MT) of various tissues contains bound zinc (Zn) and any change in Zn status can alter its synthesis and tissue deposition. The changes in MT levels and its inducibility in Zn-injected and Zn-deficient (Zn-D) rats were studied. MT levels in 11 tissues (brain, lung, heart, liver, kidney, stomach, small intestine, pancreas, spleen, testes and muscle) of control and rats injected with different doses of ZnSO₄ (20 mg Zn/kg for 2, 4 or 7 times) were measured by the cadmium-hemolysate (Cd-hem) method. A dose dependent increase in MT levels was observed only in the pancreas, liver, small intestine and kidney after ZnSO₄ injection — the highest level being in the pancreas. A positive correlation was found between Zn and MT concentrations and also the relative inducibility of MT was similar in these 4 tissues (slopes of regression equations were 12.6–15.5). In order to study the effect of Zn-D in MT induction, rats were fed a diet containing 1 ppm Zn for 18 days and CdCl₂ (1 mg Cd/kg) was injected subcutaneously 3 times at 48-h intervals to control and Zn-D rats. Although the tissue distribution of Cd was similar in both the groups, MT concentrations in pancreas and kidney were significantly decreased in Zn-D. The plasma and tissue levels of Zn were also decreased in Zn-D rats injected with CdCl₂. The decrease in both Zn and MT levels was more prominent in pancreas than other organs of Zn-D rats. The results suggest that of all the organs studied, the induction of pancreatic MT is sensitive to Zn status and Zn may be a primary inducer of MT.     

Comparison of metallothionein determination by polarographic and cadmium-saturation methods

Metallothionein is a low-molecular-weight protein with a large cysteine content and a high affinity for metals. These properties were utilized in the determination of metallothionein by a polarographic method and by a cadmium saturation method. In this study, these two methods were compared for the estimation of metallothionein from rat liver and kidney after injection with CdCl₂ and ZnSO₄. Rats were injected ip with CdCl₂ (0.6 mg Cd/kg) or ZnSO₄ (10 mg Zn/kg); liver and kidneys were removed after 16 or 32 hr for metallothionein estimation by both methods. Comparison of the results showed good agreement in liver and kidney (correlation coefficient, r = 0.92 and r = 0.95, respectively). The values obtained by the polarographic method were slightly higher than those by the Cd-saturation method. A dose-dependent increase in metallothionein levels was also observed by both methods when the rats were injected repeatedly (1, 3, 5, or 10 times) with CdCl₂ (1 mg Cd/kg). There was relatively good agreement between these two methods on the determination of both hepatic and renal metallothioneins containing zinc and cadmium.     

Effect of dietary vitamin E on nitrite-treated rats

The effect of dietary vitamin E on cellular responses to nitrite was studied in rats. One-month-old male Sprague-Dawley rats were fed a basal vitamin E-deficient diet with or without 100 ppm vitamin E and 1000 ppm sodium nitrite (NaNO₂) for 9 weeks. In addition to a high mortality rate, nitrite-fed rats maintained on a vitamin E-deficient diet exhibited a marked increase in liver necrosis, tubular nephrosis and myodegeneration, as well as greater biochemical and hematological alterations when compared to the control animals. No animal mortality or histopathologic lesions in any tissues were observed in rats receiving a vitamin E-supplemented diet with or without nitrite. The results suggest that depletion of vitamin E renders rats more susceptible to the adverse effect of nitrite, and that nitrite administration potentiates deficiency of vitamin E in rats.     

Modulation of pulmonary p-nitroanisole O-demethylase by intratracheally instilled heavy metal salts

Isolated, ventilated, and perfused rat lung preparations were used to investigate the acute effects of intratracheally applied heavy metal salts on the O-demethylation of p-nitroanisole (NA). The NA O-demethylase activity of the lung was characterized by induction (104%) following pretreatment of rats with β-naphthoflavone (BNF, 80 mg/kg), and by inhibition with SKF-525A (50 μm), metyrapone (0.1 mm), or ventilation of the lungs with CO. Pretreatment of rats with indomethacin (25 mg/kg × 3 days, po) or 3-amino-1,2,4-triazole (1 g/kg, ip) did not alter this activity. The NA O-demethylase was, therefore, suggested to be mixed function oxidase (MFO). Intratracheal instillation of NiCl₂ (0.1 or 1.0 μmol/lung) inhibited the O-demethylase activity (30 or 54%, respectively). The apparent K_m of the reaction (0.138 mm) was doubled by NiCl₂ treatment (0.252 mm), and the V_max was decreased from 26.8 to 20.9 nmol p-nitrophenol/min/g. Cadmium chloride (1.0 μmol/lung) increased the activity by 80%, but the K_m was unchanged. No effect was observed at a dose of 0.1 μmol CdCl₂/lung. At doses of 0.1 or 1.0 μmol/lung, CoCl₂ was without measurable effect on this activity. These data suggest that heavy metals present in the atmosphere can interact with pulmonary MFO in low concentrations to alter the metabolism of xenobiotic compounds.     

Relationship between the development of hepato-renal toxicity and cadmium accumulation in rats given minimum to large amounts of cadmium chloride in the long-term: preliminary study

We wished to clarify the relationship between the sensitivity to induce hepato-renal toxicity and the level of cadmium (Cd) in the organs of rats exposed to minimum to large amounts of cadmium chloride (CdCl₂). For this purpose, groups of female Sprague-Dawley (SD) rats, each consisting of 24 animals, were fed diet containing CdCl₂ at concentrations of 0, 8, 40, 200, and 600 ppm for 2, 4, and 8 months from 5 weeks of age. All surviving rats given 600 ppm Cd were killed at 4␣months because of deterioration of their general condition. Animals of this group showed anemia and decreased hematopoiesis in the bone marrow, in addition to reduction of cancellous bone in their femurs. Hepatotoxicity was observed after 2 months in the groups treated with 200 ppm. By 4 months, the rats in the 600 ppm group had developed periportal liver cell necrosis. Renal toxicity characterized by degeneration of proximal tubular epithelia was apparent in the groups treated with 200 ppm from 2 months, becoming more prominent in the high-dose rats at 4 months. Hepatic accumulation of Cd increased linearly with the duration of treatment. In contrast, the concentration of Cd in the renal cortex of rats treated with 600 ppm reached a plateau level of ∼250 μg/g within the first 2 months. The renal concentration of Cd in the 200 ppm group when renal toxic lesions were first detected at 2 months ranged from 104 to 244 μg/g. No renal lesions were observed in the 40 ppm group after 8 months, despite the presence of 91–183 μg/g of Cd in the kidneys. The results thus suggest that renal toxicity would not be induced by treatment with minimum amounts of CdCl₂ for periods longer than 8 months, although accumulation of Cd might gradually progress. A further 2-year feeding study of CdCl₂ and Cd-polluted rice is now in progress. Received: 26 January 1998 / Accepted: 26 May 1998     

Toxicity of minimal amounts of cadmium to the developing rat lung and pulmonary surfactant

Pregnant rats were injected subcutaneously with 0, 1, 2, 4 or 8 mg cadmium chloride/kg each day during mid-gestation from day 12–15. Dams were sacrified on day 21. The treatment resulted in a dose-related increase in prenatal mortality, and decreases in body weight, lung weight and saturated fatty acid containing lecithin content in the fetus but no change in pulmonary sphingomyelin. Although the lowest dose produced no changes in fetal viability, body weight or lung weight, a significant reduction in the amount of saturated fatty acid containing lecithin occurred. Since saturated fatty acid containing lecithin is a major component of pulmonary surfactant, fetuses from CdCl₂-treated dams may be subject to respiratory distress postnatally.     

Short term inhalation toxicity of a liquid aerosol of glutaraldehyde-coated CdS/Cd(OH)2 core shell quantum dots in rats

Quantum dots exhibit extraordinary optical and mechanical properties, and the number of their applications is increasing. In order to investigate a possible effect of coating on the inhalation toxicity of previously tested non-coated CdS/Cd(OH)₂ quantum dots and translocation of these very small particles from the lungs, rats were exposed to coated quantum dots or CdCl₂ aerosol (since Cd²⁺ was present as impurity), 6 h/d for 5 consecutive days. Cd content was determined in organs and excreta after the end of exposure and three weeks thereafter. Toxicity was determined by examination of broncho-alveolar lavage fluid and microscopic evaluation of the entire respiratory tract. There was no evidence for translocation of particles from the respiratory tract. Evidence of a minimal inflammatory process was observed by examination of broncho-alveolar lavage fluid. Microscopically, minimal to mild epithelial alteration was seen in the larynx. The effects observed with coated quantum dots, non-coated quantum dots and CdCl₂ were comparable, indicating that quantum dots elicited no significant effects beyond the toxicity of the Cd²⁺ ion itself. Compared to other compounds with larger particle size tested at similarly low concentrations, quantum dots caused much less pronounced toxicological effects. Therefore, the present data show that small particle sizes with corresponding high surfaces are not the only factor triggering the toxic response or translocation.     

The induced synthesis of metallothionein in various tissues of rat in response to metals. I. Effect of repeated injection of cadmium salts

Even though the induced synthesis of metallothionein (MT) after exposure to metals has been known for some time, there is little data on the quantitation of MT in various tissues. In this study we have measured MT levels in eleven different-tissues of rat after injection of CdCl₂ and also compared the relative MT inducibility of these tissues. Over a period of 16 days, rats were injected subcutaneously once every second day with either saline or 3 different doses — 0.8, 1.5 or 3 mg (7.2, 13.4 or 26.8 μmol)Cd/kg of CdCl₂ and sacrificed 48 h after the last injection. Cadmium and MT were determined in brain, lung, heart, liver, kidney, stomach, small intestine, pancreas, spleen, testes and muscle. A dose dependent increase in MT accumulation was observed in a number of tissues after CdCl₂ injection, the highest amount bein in liver, kidney and pancreas. Futher analysis of the data showed a positive correlation between Cd and MT concentrations in 8 tissues. The relative MT inducibility in liver, pancrease, heart and stomach in response to Cd injection was identical.     

Differential effect of dietary selenium on the long-term neurotoxicity induced by MDMA in mice and rats

We examined the effect of dietary selenium (Se) on the long-term effect of 3,4-methylenedioxymethamphetamine (MDMA) on dopamine (DA) and 5-hydroxytryptamine (5-HT) containing neurons in the brain of mice and rats. Animals were fed either a Se-deficient (<0.02 ppm) or Se-replete (0.2 ppm) diet for 8 weeks. On the seventh week mice received three injections of MDMA (15 mg/kg, i.p. 3 h apart) or saline and rats a single dose of MDMA (12.5 mg/kg i.p.) or saline. All animals were sacrificed 7 days later. MDMA administration to mice depleted striatal DA concentration in both dietary groups, although depletion was considerably larger in the Se-deficient mice (64%) than Se-replete mice (30%). In addition, a decrease in 5-HT (17-32%) occurred in brain regions of Se-deficient but not Se-replete mice. In rats, MDMA decreased cortical [(3)H]-paroxetine binding (62%) and 5-HT content, the depletion being similar in the Se-deficient and Se-replete groups. No DA loss occurred in either group. There was no difference in the hyperthermic response induced by MDMA in Se-deficient or Se-replete animals. The Se-deficient diet decreased glutathione peroxidase (GPx) activity by 30% in mouse striatum and cortex and increased the degree of lipid peroxidation in cortical synaptosomes. Se-deficient rats also showed a decrease in brain GPx activity compared with the Se-replete group, but the degree of lipid peroxidation in synaptosomes was similar in both dietary groups. These results suggest that the antioxidant capacity of rats and mice differ leading to a differential susceptibility to the oxidative stress caused by MDMA in situations of low dietary Se.     

Estrogen-like effects of diet-derived cadmium differ from those of orally administered CdCl(2) in the ERE-luc estrogen reporter mouse model

Cadmium (Cd), an environmental and dietary contaminant, has been described to mimic the effects of 17β-estradiol (E₂) in selected model systems when studied as an inorganic salt. However, inorganic Cd salts do not represent the main form of Cd exposure in general human populations. The aims of this study were to compare the estrogen-like effects and the bioavailability of dietary Cd to inorganic CdCl₂. Adult ovariectomized ERE-luc reporter mice were administered two bread based diets containing different concentrations of Cd (17.57 and 49.22 μg/kg, corresponding to oral intakes of 1.8 and 5.1 μg/kg body weight (bw) per day, respectively), inorganic CdCl₂ (1 μg/kg bw per day by gavage) or E₂ (5 μg/kg bw per day pellet) for 21 days. The effects on estrogen signaling were investigated by studying the uterine weights, luciferase activation, and expression of endogenous estrogen target genes. The uterine weight was significantly increased by both CdCl₂ and E₂ but not by the Cd containing diets. All treatments modulated the expression of luciferase and the endogenous estrogen target genes; however, there was no consistent overlap between the responses triggered by the bread diets and the responses stimulated by CdCl₂ or E₂. Oral exposure to Cd was calculated and the concentrations in liver and kidneys quantified to estimate the amount of absorbed Cd retained in tissues. The results suggest significantly lower absorption and/or tissue retention of dietary Cd compared to CdCl₂ following oral exposure. Altogether, our results support previous reports on in vivo estrogenicity of CdCl₂ but do not suggest the same activity for diet bound Cd. This study calls for caution when extrapolating results from pure compound studies (e.g. estrogenicity of CdCl₂) to dietary exposure scenarios (e.g. estrogenicity of diet bound Cd). Further basic research is needed on the mechanisms of interaction between Cd and the estrogen signaling, biologically active species of Cd, and biomarkers of estrogen-like effects of Cd in vivo before human health risk assessment on the hormone disruptive effects of Cd can be carried out.     

The effects of intermittent nitrogen dioxide exposure on vitamin E-deficient and -sufficient rats

In two separate experiments rats fed vitamin E-deficient, normal or high vitamin E-supplemented diets were intermittently exposed to 15 ppm ± 1.0 ppm nitrogen dioxide (NO₂) over a 5-week (4 days/week, total of 31.5 h exposure) or an 18-week (5 days/week, total of 93.5 h exposure) period. In the 5-week, NO₂-exposed rats, the blood methemoglobin levels were not influenced by NO₂ exposure or the level of vitamin E in the diet. Tissues of the rats exposed to NO₂ for 18 weeks showed some histological changes; in the lung, increased atelectasis and alveolar thickening and in the liver, increased granular changes, karyolysis and karyorhexis. These differences were suppressed by increasing levels of dietary vitamin E. Tissue lipofuscin pigment (LFP) concentrations were not affected by NO₂ exposure or dietary vitamin E. Fatty acid distribution of lung lipid extracts showed no changes due to NO₂ exposure; however, some effects of dietary vitamin E could be seen. The results suggest that intermittent NO₂ exposure, under the described conditions, did not cause ultimate changes of the biochemical parameters measured.