RESUMO
At the level of exposure employed (approximately 14.0 ppm NO2 or 0.85 ppm O3) epithelial cells at the juncture of the terminal airways and proximal alveoli have previously been shown to be seriously injured or destroyed in maturing (35 days of age or older) and adult lungs. Subsequent repair results in the formation of a tissue nodule at this location. In contrast, postnatal rats between birth and weaning have been shown to be highly resistant to the cytotoxic effects of both NO2 and O3. Prior to wearning, exposure to O3 resulted in little or no injury when examined with either the light or electron microscope, and only minor injury and loss of cilia from epithelial cells lining the terminal airways was noted after NO2 exposure. Subsequent to weaning at 20 days of age, however, there was a progressive increase in the cellular response in both the terminal airways and proximal alveoli after exposure to either oxidant gas. A plateau in the response is reached at approximately 35 days of age and continues until the animals are approximately 1 year old. The data are discussed in terms of current theories on endogenous antioxidant mechanisms.
Assuntos
Animais Recém-Nascidos/anatomia & histologia , Pulmão/efeitos dos fármacos , Óxido Nitroso/farmacologia , Ozônio/farmacologia , Alvéolos Pulmonares/efeitos dos fármacos , Animais , Brônquios/efeitos dos fármacos , Brônquios/ultraestrutura , Cílios/ultraestrutura , Epitélio/ultraestrutura , Pulmão/ultraestrutura , Alvéolos Pulmonares/ultraestrutura , RatosAssuntos
Pulmão/patologia , Ozônio/toxicidade , Animais , Brônquios/efeitos dos fármacos , Cílios , Exposição Ambiental , Células Epiteliais , Epitélio/efeitos dos fármacos , Pulmão/efeitos dos fármacos , Pulmão/fisiopatologia , Masculino , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Alvéolos Pulmonares/efeitos dos fármacos , Ratos , Regeneração , Fatores de TempoAssuntos
Ozônio/farmacologia , Alvéolos Pulmonares/efeitos dos fármacos , Animais , Membrana Basal/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Núcleo Celular , Citoplasma , Células Epiteliais , Epitélio/efeitos dos fármacos , Masculino , Microscopia Eletrônica , Dilatação Mitocondrial , Alvéolos Pulmonares/citologia , RatosRESUMO
The epithelial response in the terminal bronchioles and alveoli was examined after exposure to approximately 0.5 and 0.9 ppm ozone (O(3)). Loss of ciliated cells from the terminal bronchiole was pronounced after 6 to 10 hours of exposure; however, nonciliated cells were resistant to injury from O(3). In contrast, type 1 alveolar lining cells were very sensitive to O(2) and were severely damaged or removed from significant areas of the proximal alveoli after as little as 2 hours of exposure to 0.5 ppm. The basement lamina was left devoid of an epithelium with the exception of type 2 cells, which were very resistant and retained a relatively normal appearance. Under continuous exposure, repair of the lesion area was accomplished in approximately 48 hours through proliferation of the type 2 cells. The new cells were cuboidal at first but subsequently became more squamous in appearance. Exposure for 8 to 10 hours followed by residence in clean air resulted in a proliferative response at 48 hours, about equal to that observed after continuous exposure.
