Ultrastructural Alterations Produced by Polycyclic Aromatic Hydrocarbons on Rat TrachéalEpithelium in Organ Culture1

Ultrastructural alterations of columnar respiratory epithe lium were produced by certain polycyclic aromatic hydrocar bons in suckling rat trachea maintained in organ culture for 11 days. The potent carcinogens 7,12-dimethylbenz(a)anthracene (DMBA) and benzo(a)pyrene and the weakly carci nogenic compounds benz(a)anthracene and 5-fluoro-7,12-dimethylbenz(a)anthracene (F-DMBA) produced cells whose cytoplasm contained little endoplasmic reticulum, many free ribosomes, complex autophagic vacuoles, and abundant cytoplasmic filaments. These cells were often connected by many desmosomes and complex interdigitations in a stratified epi thelium 3 to 8 cells high, which bore a similarity to stratified squamous epithelia such as skin and also resembled bronchogenie carcinoma in situ. Some nucleolar fragmentation and dis organization also occurred in the epithelium of the carcinogentreated expiants. In general, DMBA produced morphologic abnormalities at low concentrations, while the related com pounds benz(a)anthracene and F-DMBA did so at concentra tions 12.5to 25-fold higher. Although autophagic vacuoles and related structures, as well as some degree of disorganization of the endoplasmic reticulum, were found in columnar cells, and increased filaments were noted in basal cells, extensive al teration of cell structure and epithelial state was not encoun tered in control expiants or in expiants treated with anthracene, benzo(e)pyrene, benzo(a)fluorene, benz(m,n,o)fluoranthene, chrysene, perinaphthoxanthene, perylene, or phenanthrene.