ACTION OF DAUNOMYCIN ON THE METABOLISM OF NUCLEIC ACIDS OF NORMAL AND NEOPLASTIC CELLS CULTURED IN VITRO

Abstract

The action of Daunomycin, an antibiotic of Rhodomycin group, on the nucleic metabolism was studied in « in vitro » normal and malignant cells. The action of Daunomycin was tested on rat fibroblasts and Hela monolayer. The autoradiographic study was carried out with two specific precursors thymidine 3H and uridine 3H; the metabolic changes produced by this substance were determined on the ground of the percentage of labelled cells and silver grains reduced per element. The results show that Daunomycin produced an inhibition on synthetic processes in Hela cells and in rat fibroblasts, but that the doses that caused an equal reduction of thymidine incorporation was higher for Hela cells than for fibroblasts. In the cultures exposed to Daunomycin for 1 hour and observed 24 and 48 hours afterwards the results suggested an immediate inhibition on thymidine incorporation and a delayed degradation of DNA. As for the RNA fraction, a low inhibition in normal cells and an higher one in malignant cells was observed. The different behavior of the two types of cells strongly suggests that a fraction with an high turnover in the neoplastic cells and a lower on in the normal cells is involved.