EFFECTS OF INORGANIC ARSENICALS ON DNA-SYNTHESIS IN UNSENSITIZED HUMAN BLOOD-LYMPHOCYTES IN-VITRO

Effects of inorganic arsenicals on DNA synthesis in unsensitized human blood lymphocytes were biphasic: The chemicals at very low concentrat ions enhanced DNA synthesis, whereas higher concentrations inhibited D NA synthesis. The concentrations of arsenicals at which the maximum st imulating effect was found were 1 x 10(-5)M, 1 x 10(-6) or 2 x 10(-6)M , and 0.8 x 10(-6) or 1 x 10(-6)M for sodium arsenite exposure of 1 h, 3 d, and 6 d, respectively; for sodium arsenate, 1 x 10(-5)M, 1 x 10( -5)M, and 2 x 10(-6) or 5 x 10(-6)M, respectively. Arsenicals must be present for the entire 6-d culture period to produce maximum stimulati on of DNA synthesis in human lymphocytes. The longer exposure of the l ymphocytes to arsenicals, the lower the concentrations of arsenicals a t which the maximum stimulating effect on DNA synthesis was found. Sti mulating effect of trivalent arsenic (sodium arsenite) on DNA synthesi s was stronger than pentavalent arsenic (sodium arsenate), and the str onger the effect of trivalent arsenic than pentavalent, the longer exp osure of the cells to the chemicals. Both sodium arsenite and sodium a rsenate stimulated. DNA synthesis in human lymphocytes to a lower degr ee than phytohemagglutinin (PHA).