Effect of oridonin and bleomycin A 5 combination on DNA syntheses in tumor and bone marrow cells

The inhibitory effect of oridonin (Orid) and bleomycin A5 (BLM) in combination on DNA syntheses in Ehrlich ascitic carcinoma, P388 leukemia and bone marrow cells both in vivo and in vitro was determined by the technique of tritium-labelled uptake method and autoradiography. The results suggested that DNA synthesis was markedly inhibited by the combination of Orid (0.5, 2μg/ml) and BLM (20, 40μg/ml) in vitro as compared to that by each drug using alone. However, RNA and protein syntheses were not significantly affected. The convergent inhibition on DNA syntheses of Orid (15mg/kg) and BLM (3 mg/kg) in combination in vivo was stronger in the tumor cells than in the bone marrow cells.