Bronchiolar epithelium

It is seen that the diameters of bronchioles (averaged over generations 11 - 15) vary little with age. The increase in bronchial size is greater, but still less than might be expected if airways are simply scaled for overall body dimensions (illustrated by the dashed curves in Figure 9, which are functions of body weight W). Since bronchiolar diameter does not change much with age it is likely that the thickness of bronchiolar epithelium is also relatively constant. However, in the case of the bronchi, it is reasonable to assume that epithelial thickness is proportional to bronchial diameter. Thus, it is necessary to use age dependent conversion factors between the surface density of alpha-decays and dose to cells. 

Fortoul, T.I. et al., Sex differences in bronchiolar epithelium response after the inhalation of lead acetate, Toxicology 207, 323, 2005. 

After intratracheal instillation of nickel chloride or nickel sulphate in rats, a modest inflammatory response with increased number of macrophages and polynuclear leucocytes was obtained, together with increased activities of lactate dehydrogenase and -glucuronidase in bronchoalveolar fluid [351]. More severe lesions were characterized by type II cell hyperplasia with epithelialization of alveoli, and in some animals, fibroplasia of the pulmonary interstitium. By inhalation in rats, the nickel salts produced chronic inflammation and degeneration of the bronchiolar epithelium [352, 353]. There was also atrophy of the olfactory epithelium and hyperplasia of the bronchial and mediastinal lymph nodes. Nickel sulphate also produced a low incidence of emphysema and fibrosis [353]. 

Papillary tumors, apparently derived from Clara cells, in the bronchiolar epithelium have been reported in a group of 12 New Zealand rabbits exposed to 3,000 ppm -hexane for 8 hours a day, 5 days a week for 24 weeks (Lungarella et al. 1984), but the incidence was not reported. 

Figure 10.1 Typical tracheo-bronchial and bronchiolar epithelia showing the major cell types. The tracheo-bronchial epithelium showing the pseudostratified nature of the columnar epithelium, principally composed of ciliated cells (C), interspersed with goblet cells (G), brush cells (Br), serous cells (S), Kulchitsky s cells (K) and basal cells (B). The bronchiolar epithelium showing the cuboidal nature of the epithelium, principally composed of ciliated cells (C), Clara cells (Cl) and infrequent basal cells. Muc = mucus Ci = cilia N = nucleus Sec = secretory granules.

Exposure of rats to 0.5 ppm 6 hours/day, 5 days/week, for 2 weeks caused lesions in the olfactory and bronchiolar epithelium along with inflammatory exudate in the lumens of the respiratory tract. ... 

In experimental animals, nitrogen dioxide induces several types of pulmonary toxicity. Decreased pulmonary function occurs in mice after chronic exposure to 0.2 ppm with daily excursions to 0.8 ppm. Effects on lung morphology were seen in rats exposed to 10 ppm for 36 hours and included cilia loss and hypertrophy of the bronchiolar epithelium. In guinea pigs acute exposure to 4 ppm caused increased airway hyperresponsiveness toward histamine. 

Those submicron particulates which enter the alveolar sacs may undergo various degrees of absorption, depending upon the solubility of their components, or are transported to the base of the ciliated bronchiolar epithelium (54). Alveolar absorptive efficiency for most trace elements is 50-80% (50). Retention or absorption is not necessarily a simple function of solubility. Silver iodide, for example, is rapidly absorbed from the lungs even though it is weakly soluble in water (56). Likewise, insoluble elemental lead deposited in the respiratory passages is absorbed, but the mechanism involved remains to be elucidated (49). Vanadium probably accumulates in human lungs in insoluble forms... 

Massaro G Massaro D (1986) Development of bronchiolar epithelium in rats. Am J Physiol, 250(5 Pt 2) R783-R788. 

For similar routes and forms of mercury, the adverse health effects seen in children are similar to the effects seen in adults. For example, a young child who was intoxicated with mercury vapor, died of pulmonary edema and had a grayish, necrotic mucosa of the stomach and duodenum (Campbell 1948). These effects are similar to those seen in adult populations occupationally exposures to inhaled metallic mercury vapors. Respiratory effects in adults from inhalation of metallic mercury vapor include pulmonary edema, lobar pneumonia, fibrosis, desquamation of the bronchiolar epithelium, and death in severe cases due to respiratory failure (Gore and Harding 1987 Jaffe et al. 1983 Kanluen and Gottlieb 1991 Matthes et al. 1958 Taueg et al. 1992 Teng and Brennan 1959 Tennant et al. 1961). 

Imamura, T., Gandy. J., and Fukuto, T. R. (19S3). An impurity of nialathion alters the morphology of rat lung bronchiolar epithelium. Toxicology 26, 73-79. 

Loss of airway epithelium was inconsistent. Some monkeys had multifocal, asymmetric denudation of bronchial epithelium, with near total loss of the bronchiolar epithelium. Former bronchioles were recognized only by their smooth-muscle walls. Scant bronchial intraluminal exudate consisted of mucoid material, neutrophils, macrophages, and sloughed, necrotic cells. 

Webb (1 ) reported that in an autoradiographic study paraquat is localized in bronchiolar epithelium 24 hafter the paraquat exposure and implicates the bronchiolar epithelium as the site of paraquat uptake. In our immunohistochemical study, we not only observed that paraquat was selectively localized in bronchiolar epithelial cells, but also observed that paraquat was secreted into the bronchiole. 

Hacked BP, Gitlm JD Cell-specihc expression of a Clara cell secretory protein-human growth hormone gene in the bronchiolar epithelium of transgenic mice Proc Natl Acad Sci USA 1992, 89 9079-9083... 

In the marmoset lung CYPlAl was detected in the connective tissue of interalveolar septa, in the bronchiolar epithelium, in the vascular and bronchiolar smooth muscle cells and in chondrocytes (Muller et al. 1999). 

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