Effects of potassium dichromate on nucleic acid and protein syntheses and on precursor uptake in BHK fibroblasts.

Treatments for 1 to 4 hr with 10-4 m potassium dichromate, a soluble hexavalent chromium salt with a strong oxidizing power, markedly reduce DNA and RNA accumulation rates in hamster fibroblasts grown in vitro (BHK line), as shown by quantitative spectrophotometric determinations. Such inhibitory action is not immediately evident on the basis of the incorporation rates of labeled nucleosides into DNA and RNA, as dichromate affects also the relative concentrations of labeled precursors in the intracellular pool. Dichromate first stimulates and then inhibits nucleoside (mostly thymidine) uptake, whereas amino acid uptake is immediately inhibited. Actual rates of macromolecular syntheses have been calculated by taking into account the induced changes of soluble precursor concentrations; sucn normalized rates point out that dichromate induces a sudden blockage of DNA replication, whereas RNA and protein syntheses are secondarily inhibited. The observed cytotoxic effects of dichromate are tentatively referred to the oxidation of cell components by hexavalent chromium and thereby to the interaction of reduced trivalent chromium with specific biological ligands on cell membrane and on DNA.