Influence of vitamin A and 3,7-dimethyl-2,6-octadienal (citral) on the effect of benzo(a)pyrene on hamster trachea in organ culture.

Abstract

Summary Benzo(a)pyrene (BaP), 10.5 µg/ml, produced cellular pleomorphic or squamous metaplastic epithelia and shrinking of cartilage matrix in suckling hamster trachea in organ culture. The squamous state appeared earlier if citral was present with BaP than if BaP alone was present in culture medium while citral alone produced abnormally differentiated epithelia without clear-cut squamous metaplasia. DNA synthesis preparatory to cell division, indicated by autoradiographic evidence of incorporation of tritiated thymidine in nuclei, was increased in some pleomorphic and metaplastic states produced by BaP alone or by BaP plus citral, but citral did not produce significant effects on proliferative activity. Vitamin A, 10 or 20 i.u./ml, produced shrinkage of cartilage matrix but sustained well-differentiated columnar epithelia with normal low degrees of replicative activity during 15 days of cultivation. When vitamin A was added to media containing BaP, columnar differentiation of epithelia was preserved. Proliferation induced by BaP was also inhibited by vitamin A in some instances and more effectively by 20 than by 10 i.u. Dissolution of cartilage matrix was greater in the presence of BaP and vitamin A. The present in vitro study demonstrates that both vitamin A and BaP act directly on the respiratory epithelium in a competitive fashion and on cartilage with an additive effect. The organ culture method thus appears applicable to the study of the mechanisms of action of vitamin A and a carcinogenic polycyclic hydrocarbon on tracheobronchial tissues.