Donald A. Creasia

Elution of benzo[a]pyrene from carbon particles in the respiratory tract of mice

The effect of carrier particle size on the rate of dissociation of benzo[alpha]pyrene (BaP) from carrier particles deposited in the respiratory tract of mice was studied. BaP-coated carbon particles (in two size ranges, 0.5-1.0 and 15-30 mum) plus 103Ru-tagged carbon tracer particles were intratracheally instilled in mice. The clearance of carbon particles and the simultaneous rate of elimination of BaP from the respiratory tract was measured. BaP adsorbed to 15- to 30-muM carbon particles was eliminated from the lung at essentially the same rate as the carbon particles were cleared. In contrast, BaP adsorbed to 0.5- to 1.0-muM carbon particles was eliminated from the lung approximately 4 times faster than the carbon particles were cleared. The persistence of carcinogens and their rates of elution from carrier particles are discussed in relation to the pathogenesis of lung cancer in animals treated with carcinogen-carrier particle preparations.The effect of respiratory infection by PR8 influenza virus on the elution of bnezo[a]pyrene (BaP) from carbon particles in the respiratory tract of mice was studied. In mice, this virus produces, among other pheneomena, a proteinaceous effusion and mixed cellular exudate in the alveolar parenchyma during the acute phase of infection. If BaP-coated carbon particles are introduced into the respiratory tract during the acute stage of infection, the rate of BaP elution from the carbon particles is increased. When BaP-coated carbon particles were instilled in the respiratory tract either 1 wk before or 2 wk after the acute stage of infection, the BaP elution rate from carbon particles were similar to that in uninfected animals.

In vivo and in vitro no2 exposures enhance phagocytic and tumoricidal activities of rat alveolar macrophages

Rat alveolar macrophages (AM) were exposed in vivo or in vitro to nitrogen dioxide (NO2) and subsequently tested for phagocytic and tumoricidal activities. AM obtained by lavage from Fischer 344/N rats exposed for 4 h to 40 ppm NO2 were significantly more phagocytic to opsonized sheep red blood cells (SRBC), exhibited an increased cytotoxic response toward syngeneic mammary adenocarcinoma cells, and were more sensitive to activation by agents such as lipopolysaccharide, muramyl dipeptide, and macrophage-activating factor, as compared with the response of AM obtained from unexposed control rats. Repeated 4 h/d NO2 exposures over 7-d or 14-d periods usually resulted in AM activity similar to control levels, with some instances of increased phagocytic activity of the AM but not to the extent of that observed for a single 4 h exposure. There were no significant decreases in the cytotoxic or phagocytic activities of the AM during any of the exposure periods. For the in vitro exposures, AM were lavaged from normal rats and then exposed for various periods to 10, 20, or 40 ppm NO2. A dose-related and time-dependent enhanced cytotoxic response of AM was observed. Maximum AM-mediated cytotoxicity occurred after an in vitro exposure to 10 ppm NO2 for 2 h. The cytotoxic response was directed toward syngeneic mammary adenocarcinoma cells but not against syngeneic embryoblast cells, indicating that the AM retained the ability to distinguish between normal and abnormal cells. No inhibitory effects of NO2 on AM-mediated cytotoxicity were observed. These experiments suggest that the host AM-mediated immune defense of the lung may be modulated by host exposure to inhaled chemicals.

Respiratory Cocarcinogenesis Studies with Ferric Oxide: A Test Case of Current Experimental Models

Laboratory studies conducted to date strongly suggest that ferric oxide dust can act as a cofactor in respiratory tract carcinogenesis. The available data indicate at least 2 different mechanisms by which these otherwise fairly innocuous particles might exert their effect: 1. by retarding carcinogen clearance (this applies to conditions in which the carcinogen is adsorbed to the particle surface) and 2. by causing cytopathological effects (irritation?, enhanced cell proliferation?) at the site of deposition.

A Tobacco Smoke Inhalation Exposure Device for Rodents

A system which utilizes a piston pump to generate cigarette smoke under standard conditions, and expose rodents to the inhalation of diluted smoke for controlled periods of time is described. Variations of the basic system have been employed to exposure groups of ten to twenty hamsters or rats, and should allow exposures of up to forty mice. The system has been in use for approximately 24 months in routine chronic exposures of rats. Data are presented to define the operating characteristics and typical dosimetry. Animal containment peculiar to this apparatus is described.

Impairment of Deep Lung Clearance by Influenza Virus Infection

This paper reports experimentally observed effects of influenza virus infection on pulmonary clearance of chromic oxide dust tagged with chromium 51 (51Cr2O3). The usual course of this viral infection produces a stage of acute pneumonitis at 10 to 14 days after exposure, with subsequent, and often permanent, fibrotic scarring of the lung tissue. When 51Cr2O3 was administered simultaneously with, or at 1, 3, 5, 9, or 56 weeks after, virus inoculation, a marked deficiency in pulmonary clearance of the dust was noted. The distribution of retained chromium in the lungs of infected animals was found to depend on the relation between time of infection and time of 51Cr2O3 administration, a relationship which suggests that individuals with respiratory infections are at increased risk from exposure to toxic and radioactive particles.

BIOAVAILABILITY OF TNT RESIDUES IN COMPOSTS OF TNT-CONTAMINATED SOIL

Composting is being explored as a means to remediate 2,4,6-trinitrotoluene (TNT) contaminated soils. This process appears to modify TNT and to bind it to organic matter. The health hazards associated with dusts generated from such materials cannot be predicted without knowing if the association between TNT residues and compost particulate is stable in biological systems. To address this question, single doses of [14C]-TNT, soil spiked with [14C]-TNT, or compost generated with [14C]-TNT-spiked soils were administered to rats by intratracheal instillation. The appearance of 14C in urine and tissues was taken as an indication of the bioavailability of TNT residues from compost particles. In rats instilled with neat [14C]-TNT, about 35% of the 14C dose appeared in urine within 3 d. The 14C excreted in urine by these rats decreased rapidly thereafter, and was undetectable by 4 wk after treatment. Similar results were obtained with soil-treated rats. In contrast, after treatment with [14C]-TNT-labeled compost, only 2.3% of the total 14C dose appeared in urine during the first 3 d. Low levels of 14C continued to be excreted in urine from compost-treated rats for more than 6 mo, and the total amount of 14C in urine was comparable to that in TNT-treated animals. Determination of the radiolabel in tissues showed that 14C accumulated in the kidneys of rats treated with labeled compost but not in rats treated with [14C]-TNT or [14C]-TNT-spiked soil. These results indicate that the association between TNT and particulate matter in compost is not stable when introduced into the lungs. Accumulation of 14C in kidneys suggests the presence of a unique TNT residue in compost-treated rats. The rate of excretion and tissue disposition of 14C in rats treated with TNT-spiked soil indicate that TNT in soil is freely available in the lungs.

Stimulation of DNA synthesis in the lungs of hamsters exposed intermittently to nitrogen dioxide

Stimulation of [3H] thymidine incorporation in the lungs of hamsters exposed singly and repeatedly to 10 ppm NO2 was studied. Within 24 hr of the first exposure to NO2, the response was characterized by a marked increase in [3H] thymidine labeling in the bronchi, bronchioles, and alveolar ducts, but not in the trachea or the peripheral alveoli. If, after the first NO2 exposure, subsequent exposures were repeated daily, no further stimulation of [3H] thymidine incorporation was observed in any part of the respiratory tract. However, if the interval between the first and subsequent exposures was 2-3 days rather than 1 day, stimulation of [3H] thymidine incorporation was observed in the bronchi, bronchioles, and alveolar ducts for up to 21 NO2 exposures. A significantly greater increase in [3H] thymidine incorporation was observed when the interval between subsequent exposures was extended to 7 days. However, no repeated exposure, whether at 2-3 or 7 day intervals, was as effective as the first NO2 exposure in stimulating incorporation of [3H] thymidine.

Pathogenesis of nitrogen dioxide-induced respiratory lesions in reference to respiratory clearance of inhaled particulates.

The pathogenesis of NO2-induced respiratory disease and the effect of NO2 on respiratory clearance of 51Cr2O3 were studied. Young adult female mice were exposed to a 51Cr2O3 aerosol, followed by a daily exposure to either 30 ppm NO2 for 2 wk or 60 ppm NO2 for 2 wk or a single exposure to 170 ppm NO2. Exposure to 30 ppm NO2 had a minimal histopathologic effect on respiratory tract tissue. Exposure to 60 ppm NO2 produced marked histopathologic effects, which were subsequently resolved. Exposure to 170 ppm NO2 produced permanent histopathologic lesions. In mice exposed to concentrations of NO2 that produced minimal histopathologic effects, respiratory clearance of 51Cr2O3 was similar to that in unexposed mice. When mice were exposed to concentrations of NO2 that produced permanent tissue damage, prolonged impairment of respiratory clearance of 51Cr2O3 was observed, despite resolution of edema produced by inhalation of NO2. At concentrations of NO2 that produced marked edema and histopathologic effects that were resolved despite repeated NO2 exposure, there was an initial marked impairment of respiratory clearance, then an accelerated rate of clearance, and finally a clearance rate similar to that of unexposed mice. The time during which accelerated clearance occurred was well correlated with the time at which the histopathologic lesions was observed to regress.

Respiratory Tract Deposition of Smoke Particles Using a Nasal Bypass Device

In order to avoid nasal absorption, an intralaryngeal cannula was tested as a device for bypassing the nose in delivering smoke into the lungs of hamsters. The intralaryngeal cannula increased lung deposition of radiolabeled smoke particles twofold to threefold over that in nose-breathing controls. Stabilization of respiration (absence of avoidance reaction), rather than prevention of nasal absorption of smoke, was demonstrated to be the cannulas major mechanism of action. Although suitable for acute exposures, the device is of limited use for chronic exposures that require daily insertion of the cannula during an extended period of time.

Stimulation of DNA synthesis in lungs of hamsters tolerant to nitrogen dioxide.

Nitrogen dioxide (NO2) is both edematogenic and cytotoxic to the lung. Preexposure to NO2 protects against mortality from formation of excessive pulmonary edema (tolerance) and, depending on the preexposure schedule, may or may not protect against the cytotoxic effects of NO2 in the lung. Measurement of DNA synthesis in hamster lung was used to study the question of whether the more subtle cytological injury induced by NO2 is mediated by a system that also exhibits tolerance. It was found that when hamsters are preexposed daily to 10 ppm NO2, they develop tolerance for normally lethal concentrations of NO2, are protected against cytological injury from 10 ppm NO2, but are not protected from the cytotoxic effects of NO2 at concentrations greater than 10 ppm. Animals exposed weekly to 10 ppm NO2 are not protected from further cytological injury induced by weekly exposures to 10 ppm NO2, but do develop tolerance for lethal concentrations of NO2. Thus, the data indicate that induction of tolerance to NO2 does not necessarily protect the cell populations of the lung from the cytotoxic effects of NO2.