Transient epithelial loss in rat larynx after acute exposure to tobacco smoke.

After a single 1 h exposure to cigarette smoke by inhalation, the degree of damage to the epithelial layer lining the ventral wall of the rat larynx has been assessed using a semi-quantitative scoring system. The damage was characterised mainly by partial or complete loss of epithelium. The time at which a maximal response was observed depended upon the smoke concentration. Regeneration was rapid and was followed by development of hyperplasia; the regenerative phase was progressively more delayed with higher concentrations of smoke. Smoke concentrations have been compared during the regenerative phase and an approximately linear dose-response relationship has been found. The causative agents were in the smoke particulate phase. The severity of the damage response may parallel the extent of subsequent hyperplasia and metaplasia. Laryngeal damage may thus provide a short-term bio-assay for the inhalation toxicity of cigarette smoke.