Cell Turnover in the Respiratory Tract

¹ Section of Experimental and Anatomic Pathology
² Section of Medicine

The turnover of cells in the respiratory tract was studied in a strain of mice of Swiss-Webster origin by the parenteral injection of tritium-labeled thymidine combined with radioautography. The findings in the epithelium of the trachea and large bronchi suggested that two cell populations existed, one with a turnover time of less than two days and the other with a turnover time of five to seven days. The turnover time of the epithelium of small bronchi was five to seven days. The findings suggested that two populations of alveolar macrophages existed, one with a turnover time of approximately seven days and the other with an apparent turnover time of 35 days. Differences in labeling were observed in a main bronchus showing acute bronchitis.