Nucleotide pool unbalance induced in cultured cells by treatments with different chemicals.

Intracellular nucleotide pools directly influence a great number of cellular activities, and their size and composition are easily altered by chemical agents. However, they are seldom examined when chemical toxicity is investigated. The importance of evaluating the effects produced at the nucleotide pool level is also discussed. Some examples are reported in which the activity of a tested chemical on nucleic acid metabolism could be detected only by taking into account the modifications induced in the precursor pool. One example is the case of hexavalent chromium, which inhibits DNA and RNA syntheses, but also affects the uptake of exogenous nucleosides, thus modifying the labelling pattern of nucleic acids in treated cells. A similar situation is observed with alkylating agents (e.g. MMS and EMS), whose induction of DNA repair synthesis is sometimes masked by the concomitant depletion of labelled nucleotides in the intracellular pool.