INFLUENCE OF GROWTH-FACTORS AND MEDIUM COMPOSITION ON BENZO[A]PYRENE-INDUCED AND VITAMIN-A-INDUCED CELL-PROLIFERATION AND DIFFERENTIATION IN HAMSTER TRACHEAL EPITHELIUM IN ORGAN-CULTURE

Tracheal organ cultures and isolated tracheal epithelial cells are fre quently used to study effects of carcinogens and retinoids on both pro liferation and differentiation of respiratory tract epithelial cells. For each of these in vitro models, optimal culture conditions have bee n established, varying in type of culture medium and composition of gr owth factor and hormone supplementation, which by themselves may influ ence cellular proliferation and differentiation. In this study, we inv estigated the influence of medium composition and growth factor supple mentation on the effect of benzo[a]pyrene (B[a]P) and vitamin A on cel lular proliferation and differentiation in hamster tracheal epithelium in organ culture. In tracheae cultured in Ham's F12 medium, cell prol iferation was decreased by B[a]P relative to untreated controls, where as vitamin A in combination with B[a]P increased cell proliferation co mpared with that in tracheae treated with B[a]P alone. The effects in tracheae cultured in CMRL-1066 medium were just the opposite: B[a]P in creased cell proliferation and vitamin A decreased B[a]P-induced proli feration. To explain this difference in cell proliferation, the effect s of various growth factors (epidermal growth factor and transferrin) and medium components (nucleotides, NAD(+)/NADP and CaCl2.2H(2)O) on B [a]P and vitamin A-induced cell proliferation were investigated. The m ain factor responsible for the different effects on cell proliferation appeared to be the concentration of Ca2+ in the culture medium; addit ion of CaCl2.2H(2)O to Ham's F12 medium resulted in effects of B[a]P a nd vitamin A on cell proliferation comparable with those observed in t racheae cultured in CMRL-1066 medium. These results clearly show that the composition of the culture medium, and particularly the concentrat ion of Ca2+, strongly influences the effect of vitamin A and B[a]P on cell proliferation in hamster tracheal epithelium in organ culture. Co pyright (C) 1996 Published by Elsevier Science Ltd