5-METHYLDEOXYCYTOSINE AS A BIOLOGICAL MARKER OF DNA-DAMAGE INDUCED BYOKADAIC ACID IN VERO CELLS

Okadaic acid (OA), a toxin produced by dinoflagellates, accumulates in the hepatopancreas of mussels and causes diarrhetic shellfish poisoni ng. This toxin is a tumor promoter and a specific potent inhibitor of protein phosphatases 1 and 2A. The effect of OA on the relative amount s of the five nucleosides (deoxycytosine, 5-methyldeoxycytosine, desox ythymidine, deoxyguanine, and deoxyadenine) in the DNA of Vero cell cu ltures was determined by high performance liquid chromatography in par allel to DNA synthesis followed by [H-3]-thymidine incorporation. OA a t a concentration of 7.5 ng/mL did not significantly inhibit DNA synth esis, but induced hypermethylation in Vero cell DNA. The level of 5-me thyl-deoxycytosine increased from 3.8 to 7.8%, indicating possible int erference of this marine toxin with DNA regulation, replication, and e xpression. Higher concentrations of OA inhibited DNA synthesis, but fa iled to increase the rate of DNA methylation. (C) 1998 by John Wiley & Sons, Inc.