The stathmokinetic and morphological response of the hamster respiratory epithelium to intralaryngeal instillations of saline and ferric oxide in saline.
Ferric oxide (Fe2O3) and saline, substances which enhance lung tumor development when intratracheally instilled with certain carcinogens, were studied for their effects on respiratory epithelial cell proliferation in Syrian golden hamsters. Groups of hamsters were given intralaryngeal instillations of 0.2 ml saline or 3 mg Fe2O3 in 0.2 ml saline (Fe2O3-saline) once a week for 5, 10, or 15 weeks; an additional group of hamsters received a single Fe2O3-saline instillation. Epithelial mitotic rates (MR, 6 hr colchicine blockade) for the midtrachea, left intrapulmonary bronchus, and left lung bronchioles were determined 32 hr after the last instillation for each group. No change in the MR was seen at any airway level for any of the saline-treated groups. There was also no change in the MR of the trachea or bronchus for any of the groups treated with Fe2O3-saline. The MR of the bronchioles was increased after 5 instillations of Fe2O3-saline. Fe2O3-saline instillations also caused bronchioloalveolar hyperplasia (BAH) to develop by 5 instillations, but after 10 and 15 treatments BAH was less prominent. These data indicate that intralaryngeal Fe2O3-saline instillations result in focal cell injury followed by proliferation in the distal airways, but multiple long-term treatments produce an adaptive response of the respiratory epithelium.
Marshall, HE; Keenan, KP; McDowell, EM
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