INCREASED INVITRO GROWTH CAPACITY OF TRACHEAL EPITHELIUM EXPOSED INVIVO TO 7,12-DIMETHYLBENZ(A)ANTHRACENE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 37  (6) , 1811-1821
Abstract
Heterotopic tracheal transplants of rats were exposed in vivo to 150 or 640 .mu.g of 7,12-dimethylbenz(a)anthracene (DMBA) delivered over 2 wk, and the epithelium was studied in vitro in an attempt to identify changes in growth behavior during early phases of neoplastic development. Explants were made from the exposed tracheas, as well as a series of controls, and the rate of epithelial outgrowth from the explants was measured. The capacity of the outgrowths to survive as primary cultures and their ability to survive multiple in vitro passages were studied. During the initial planting, the rate of outgrowth was greatest from explants preexposed to 150 .mu.g DMBA. Outgrowth from explants preexposed to 640 .mu.g DMBA was sparse during the 1st planting but increased during repeated planting when insulin- and hydrocortisone supplemented medium was used. Establishment of outgrowth during repeated planting of carcinogen exposed tracheal pieces was hormone dependent. Control explants did not exhibit this hormone dependency. Primary cultures could be established from only 3 of 6 explants preexposed to 150 .mu.g DMBA. These explants were initiated in insulin- and hydrocortisone supplemented medium. The primary cultures were successfully subcultured. Primary cultures were also established from 5 explants preexposed to 640 .mu.g DMBA and cultured in hormone supplemented medium. At least 1 cell line was obtained from each of the explants. To establish and maintain primary cultures from control tracheas required an enriched medium containing amino acid supplements, sodium pyruvate and putrescine, as well as the hormone supplements. Such cultures could not be subcultured. The primary cultures from carcinogen exposed explants and the subsequently developed cell lines exhibited morphological characteristics of keratinizing squamous epithelium. These characteristics include epitheloid cell morphology, multilayering and sloghing of orangeophilic squamous cells and the presence of keratohyalin granules. These experiments demonstrate increased in vitro growth capacity of tracheal epithelium after a short in vivo exposure to carcinogen.