We have previously reported that the selective radiation of the rat trachea produced histological features similar to those seen in the lungs of the autopsy cases of congenital esophageal atresia associated with tracheoesophageal fistula. The present communication describes biochemical findings obtained in conjunction with histologic studies.
Twenty male rats of Donryu strain weighing 200-310g were subjected to lineac X-ray radiation exclusively of the trachea at a dose of 500 rads per day for 30 consecutive days. The rats were sacrificed 35 days after completion of radiation schedule and their lungs were removed for lavage to measure alveolar surfactant, cellular components and rate of surfactant synthesis after intravenous injection of C14 palmitate. The levels of pulmonary surfactant and cellular components in the alveolar space were much higher in the experimental rat than the control. The removal rate of surfactant from the alveolar space was sigficantly reduced in the experimental rat.
The results of these studies indicated that depletion of cilia associated with squamous metaplasia of the tracheal wall induced by selective X-ray radiation resulted in an accumulation of surfactant and macrophages in the alveolar space. These findings are consistent with the view that at least part of the pulmonary surfactant and alveolar macrophages is removed from the airspace via the respiratory tract by means of the mucociliary transport mechanism.
