Alteration of intracellular DNA and RNA patterns by liver arginase studied with flow cytometry

Previous study of lymphocyte proliferation in the presence of liver arginase has indicated that arginine-depletion in the culture medium plays an important role in inhibiting cell proliferation. The inhibitory effect of both liver arginase and arginine-free condition on DNA, RNA and protein syntheses in PHA-stimulated lymphocytes were studied in cultures by measuring the incorporation of labeled precursors. Simultaneously, their influence on DNA and RNA contents in cells stained by acridine orange was investigated by automated flow cytometry. With 3 micrograms/ml arginase, the syntheses of DNA, RNA and protein were markedly inhibited after 72 h of culture. The degrees of inhibition were close to that induced in an arginine-free condition. The DNA and RNA contents of the individual cell, either cultured with 3 micrograms/ml arginase or in arginine-free medium, were arrested in G0/G1 phase. The results of cell arrest in G0/G1 phase were similar whether the cells were cultured for 24, 48 or 72 h.