Peculiarities of the proliferative activity of the aggregates forming upon recombination of the embryonic lung epithelium and mesenchyme in the intact and carcinogen-treated mice

Methods are presented of separation of the mouse embryonic lung mesenchyme (M) and epithelium (E) and of obtaining homolinear and heterolinear organotypic aggregates of E and M from intact and urethane-treated (transplacentally) A and C57BL mouse embryos. In the aggregates formed by E and M from the experimental A embryos, the index of labelled nuclei (³H-thymidine incorporation) in both the tissue components was several times that in the aggregates of E and M from the intact embryos. M from the experimental embryos aggregated with E from the intact embryos increased the proliferative activity of the latter 4 to 11 times, whereas M of the intact embryos aggregated with E of the experimental embryos decreased its proliferative activity to the normal level. A suggestion is put forward that the embryonic lung mesenchyme plays an important role in the realization of transplacental carcinogenic influences and in the development of lung epithelial tumours.