CHANGES IN THE RAT LUNG AFTER EXPOSURE TO RADON AND ITS PROGENY - EFFECTS ON INCORPORATION OF BROMODEOXYURIDINE IN EPITHELIAL-CELLS AND ON THE INCIDENCE OF NUCLEAR ABERRATIONS IN ALVEOLAR MACROPHAGES

The aim of this study was to investigate some responses of cells in th e rat respiratory tract as a function of time after inhalation exposur e to various levels of radon and its progeny. Rats were exposed to a c onstant concentration of radon and its progeny to give cumulative expo sure levels of 120, 225, 440 and 990 working level months (WLM). An ad ditional unexposed group of rats served as controls. The end points se lected for investigation were (a) the incorporation of bromodeoxyuridi ne (BrdU) in epithelial cells of the conducting airways and of the alv eolar region of the respiratory tract and (b) the incidence of alveola r macrophages with nuclear aberrations. After exposure, the incidence of epithelial cells incorporating BrdU-the labeling index-increased in all regions of the respiratory tract examined, but the increase occur red later in alveolar than in airway epithelial cells. The highest lab eling index was found in bronchial epithelial cells, which probably re ceived the highest radiation dose. After an initial induction period, the incidence of alveolar macrophages with nuclear aberrations also in creased. The possibility of using the labeling index of alveolar and a irway epithelial cells, and/or the incidence of nuclear aberrations in alveolar macrophages, to estimate the radiation dose to various regio ns of the respiratory tract after exposure of rats to radon and its pr ogeny is discussed.