DEVELOPMENTAL ABNORMALITIES AND DNA-PROTEIN CROSS-LINKS IN SEA-URCHINEMBRYOS EXPOSED TO 3 METALS

Two sublethal responses were used to investigate the effects of genoto xic metals on embryos of the purple sea urchin, Strongylocentrotus pur puratus. In addition to the standard measurement of developmental succ ess, we used a novel genotoxic response, DNA-protein crosslink (DPC) i nduction, to assess the effects of embryo exposure to pentavalent arse nate (As!, nickel (Ni) and hexavalent chromate (Cr). The procedure for sea urchin embryo DPC measurement was adapted from a mammalian cell a ssay using potassium-SDS precipitation and a DNA fluorochrome to quant ify relative amounts of free and protein-bound DNA. Developmental abno rmality and DPCs increased after a 48-h exposure to each of the three metals. Lowest observable effect concentrations (LOECs) for developmen t were 0.011 mg l(-1) As, 0.40 mg l(-1) Ni, and 2.5 mg l(-1) Cr. LOECs calculated for the DPC response to these same three metals were 0.023 , 8.01 and 10.0 mg l(-1), respectively. DPCs were transiently high in control embryos through the blastula stage, which is prior to the dram atic increase in transcription of the embryonic genome. By the gastrul a and prism stages (subsequent to embryo gene transcription), there wa s a significant decrease in DPCs. Ni-exposed embryos exhibited the gre atest magnitude of adverse effect in embryos exposed through the blast ula stage, as compared to those exposed from blastula through late gas trula stage. We hypothesize that stage-sensitivity to Ni in sea urchin embryos may be related to the induction of persistent DPCs, and the p revention of normal transcription of the embryonic genome. (C) 1997 El sevier Science B.V.