EFFECTS OF ARSENIC ON DNA-SYNTHESIS IN HUMAN-LYMPHOCYTES STIMULATED BY PHYTOHEMAGGLUTININ

Effects of arsenic on DNA synthesis in human lymphocytes were biphasic : either trivalent (arsenic trioxide and sodium arsenite) or pentavale nt (sodium arsenate) arsenic compounds at very low concentrations enha nced DNA synthesis in human lymphocytes stimulated by phytohemagglutin in (PHA), whereas higher concentrations inhibited DNA synthesis. There were differences among individual susceptibities to arsenic-induced D NA synthesis. Either stimulating or inhibiting effects of trivalent ar senic on DNA synthesis in PHA-stimulated lymphocytes were always stron ger than those of pentavalent arsenic. It was also shown that both tri valent and pentavalent arsenic could be rapidly taken up into the huma n lymphocytes, and immediately stimulated or inhibited DNA synthesis. A possible dual effect of arsenic at very low concentrations as both c omutagen and inhibitor of mutagenesis is discussed.