David L. Coffin

Metal toxicity for rabbit alveolar macrophages in vitro

Abstract A model system in vitro has been employed to assess the relative cytotoxic properties of soluble salts of metals that occur as environmental contaminants. Rabbit alveolar macrophages obtained by lung lavage were exposed in tissue culture for 20 hours to chlorides of Cd2+, Ni2+, Mn2+, and Cr3+ and to ammonium vanadate (VO3−). All metals except Cd2+ produced significant decreases in numbers of cells at concentrations that affected cell viability. Cd2+ was unique in decreasing cell viability without causing cell lysis. In comparing the relative cytotoxicity of the various metals, the number of viable cells remaining after 20 hours was expressed as a percent of the total number of cells in control cultures at 20 hours. Thus, the net number of viable cells was decreased to 50% of control at concentrations of 0.1 m m Cd2+ and VO3− or 4–5 m m Ni2+, Mn2+, and Cr3+. The specific activity of acid phosphatase, a lysosomal indicator enzyme, was also decreased at similar concentrations. Using scanning electron microscopy it was possible to correlate surface alterations with exposure concentrations and cell viabilities so as to suggest a mode and sequence of cell injury which may ultimately lead to cell death.

Similarity between man and laboratory animals in regional pulmonary deposition of ozone.

Predicted pulmonary ozone (O3) dose curves obtained by model analysis of the transport and removal of O3 in the lungs of guinea pigs, rabbits, and man indicate that a general similarity exists among these species in the shapes of the dose curves. An overview of the major features of the lower airway mathematical model used is presented. This model predicts that the respiratory bronchioles receive the maximum O3 dose. For exposures corresponding to tracheal O3 concentrations greater than 100 micrograms/m3 (0.05 ppm), the predicted respiratory bronchiolar dose for rabbits was found to be twice that for guinea pigs and 80% of that for man. Sensitivity analyses are presented for model parameters relating to the treatment of the chemical reactions of O3 with the mucous layer. The role of tidal volume in the determination of pulmonary uptake of O3 in man is examined. The consistency and similarity of the dose curves for the three species lend strong support to the validity of extrapolating to man the results obtained on animals exposed to O3.

Cytotoxic effects of vanadium on rabbit alveolar macrophages in vitro

Because of the suspected action of lung irritants on pulmonary defense mechanisms, studies were performed in vitro to assess the potential toxicity of vanadium oxides on rabbit alveolar macrophages. Alveolar macrophages obtained by lung lavage and maintained in supplemented Medium 199 were exposed to particulate forms of vanadium pentoxide (V2O5), vanadium trioxide (V2O3), or vanadium dioxide (VO2). Cell viability after a 20-hr exposure was reduced by 50% at approximately 13 μg V/ml as V2O5, 21 μg V/ml as V2O3, and 33 μg V/ml as VO2. Cytotoxicity was determined to be directly related to solubility in the order V2O5 > V2O3 > VO2. When V2O5 was dissolved in media prior to exposure of cells, only about 9 μg V/ml was required to reduce viability by 50% and to decrease total cell numbers by 70% in 20 hr as compared to control cultures. Dissolved V2O5 at 6 μg V/ml also reduced phagocytosis of polystyrene-latex spheres by about 50% as compared to controls after 20 hr. Exposure of cells or cell-free sonicates to dissolved V2O5 at concentrations as high as 50 μg V/ml produced only small changes in the specific activities of lysozyme or β-glucuronidase. However, acid phosphatase in the cell-free system was 70% inhibited by dissolved V2O5 at 1 μg V/ml. These findings suggest that exposure to vanadium oxides may alter alveolar macrophage integrity and function to the detriment of pulmonary defense.

Influence of exposure mode on the toxicity of NO2.

Pollutant gases are subject to a variety of physical and chemical interactions within the atmosphere due to cyclic production and various meteorological influences. In consequence there is generally a diurnal concentration profile for NO2 which consists of peaks of short duration and irregular occurrence superimposed on a low background. Since this variation could play an important role in the toxic effect of NO2, the influences of various exposure modes was studied. Continuous and intermittent exposure studies were used to determine the relationship between biological response and length of exposure to various concentrations of NO2. As the concentration decreased, the slope of the regression line decreased. After adjusting for total differences in the product concentration x time, the response for the two exposure modes was essentially the same. When a constant concentration x time level was employed, a short-term exposure to a high concentration produced a greater effect than exposure to a lower concentration administered over a longer period. Using these curves, the relationship between level of effect, concentration, and time can be determined. Results of these studies indicated that the frequency and amplitude of short-term peaks are of significance even though the exposure is interrupted with periods of zero concentration of NO2.

Changes in Dogs’ Lungs After Long-Term Exposure to Ozone

Dogs were exposed to 1 to 3 ppm of ozone (O3) 8 to 24 hours daily for 18 months. Macrophages appeared and increased with “dosage.” Fibrous elements were deposited rarely at the lowest dosage but increased with the concentration of O3. Additional features were thickening of the terminal and respiratory bronchiolar walls at the higher concentrations and their infiltration by lymphocytes, plasma cells, and “fibroblasts” that formed peribronchiolar collars. Connective tissue obstructed alveolar openings into bronchioles and ducts and extended into alveolar walls. Thick bronchiolar walls reduced the caliber of small airways. Bronchiolar epithelial changes included an increase in the proportion of mucus-forming cells and squamous metaplasia of columnar and cuboidal cells with occasional islands of hyperplasia. Metabolic effects were reflected in ultrastructural alteration of preexisting, intracytoplasmic bodies. Together with nitrogen dioxide, O3 may contribute to pulmonary disease in a susceptible population.

Role of time as a factor in the toxicity of chemical compounds in intermittent and continuous exposures. part II. effects of intermittent exposure

Because of fluctuations in levels of industrial air pollution linked to weather and other factors, a joint U.S.‐Soviet research team studied differences in the effect of time in exposures of air‐breathing animals to controlled varied concentrations of air pollutants. An experimental model environment was used to investigate the effects of nitrogen dioxide (NO2), sulfur dioxide (SO2), and benzene (C6H6) in the air environment of laboratory animals, with both continuous and intermittent exposures. For intermittent exposures the investigators used amounts of toxic gases whose cumulative total equaled the total in the continuous exposures, and intercalated the intermittent exposures with periods of nonpolluted air. To equal the cumulative total concentration of the single continuous exposures over an equal time period, the concentrations of toxic gases were necessarily greater in the intermittent exposures. Part I of this work deals with the effects of continuous exposure to C6 H6 on the central nervous syste...

Chronic Exposure to Nitrogen Dioxide

Squirrel monkeys continuously exposed to 1 ppm of nitrogen dioxide (NO2) for 493 days were challenged five times with monkey-adapted influenza A/PR/8/34 virus. All monkeys exposed to NO2 produced serum neutralization antibody within 21 days after virus infection, whereas only one control monkey exposed to filtered air showed comparable response. The differences observed in hemagglutination-inhibition antibody titers, body temperatures, respiratory functions, body weights, and hematological values between the experimental and control monkeys were not significant. Histopathologic examination of lung tissues indicated slight emphysema and thickened bronchial and bronchiolar epithelium only in monkeys exposed to NO2 and challenged with the influenza virus. Transmission election microscopic examination did not disclose any ultrastructural changes that could be attributed to the experimental exposures.

Nasopharyngeal removal of ozone in rabbits and guinea pigs.

In estimating pollutant concentrations responsible for observed pulmonary effects, nasopharyngeal removal of the pollutant plays an important role. The nasopharyngeal removal of ozone (O3) in anesthetized male guinea pigs and male and female rabbits was determined by drawing O3 through the isolated upper airways at a constant flow rate which approximated the animals respiratory minute volume. The tracheal O3 concentration in rabbits and guinea pigs was markedly similar and was linearly related to the chamber concentration of O3 over a range of 196--3920 micrograms/m3 (0.1--2.0 ppm O3). Regression analyses showed that O3 removal in the nasopharyngeal region is approximately 50% in both species. Both rabbit sexes responded similarly over the concentration range studied. Exposures of guinea pigs to O3 concentrations between 3920 and 5880 micrograms/m3 (2.0 and 3.0 ppm) showed that, at these higher concentrations, relatively more O3 is removed by the upper airways.

Sulfuric acid and Streptococci clearance from respiratory tracts of mice

The inhalation of 15 mg/cu m (3.2mu count median diameter) of H2SO4 aerosol for four hours after exposure to radioactive aerosol resulted in a reduction in the rate of clearance of nonviable streptococci from the lungs and noses of mice. A second exposure to H2SO4 lasting 90 minutes (15 mg/cu m, 3.2mu count median diameter) for four days prior to the radioactive aerosol resulted in a reduced rate of clearance of nonviable streptococci from the noses but not the lungs. Neither of these exposure regimens caused an alteration in the rate of reduction of viable streptococci from the lungs or noses. Inhalation of 1.5 mg/cu m of H2SO4 (0.6mu coung median diameter) for four daily 90-minute exposures prior to, or for four hours after exposure to Streptococcus caused no alteration in the normal rate of clearance of viable or nonviable streptococci from the noses or lungs.

Toxic effects of cadmium on ciliary activity using a tracheal ring model system

Abstract Experiments were performed to measure the effect of trace metals on ciliary activity using isolated hamster tracheal rings in an in vitro organ culture system. Dose—time response studies for various Cd concentrations and for lengths of exposure were conducted. Statistically significant reductions in ciliary activity occurred at concentrations as low as 0.006 m m of Cd. Validation of these in vitro results occurred when hamsters were exposed in vivo to a CdCl 2 aerosol of 2 μm particles at concentrations of 50 to 1420 μg/m 3 . The length of time required for complete recovery was also studied following various exposure regimens. Since the effectiveness of the mucociliary escalator depends on normal functioning of the ciliated epithelium, it follows from the data presented that inhalation of this metal can inhibit the normal mucociliary function vital for clearance of agents from the respiratory tract.