Toxicological studies with primary cultures of chick embryo cells: DNA fragmentation under the influence of DNase I-inhibitors.

Chicken embryo brain and liver cells in vitro exhibited spontaneous DNA fragmentation as determined by viscometry of alkaline cell lysates. Ca2+ and Mg2+ enhanced, while Zn2+, the Ca2+ chelator ethylenglycol-bis(beta-aminoethyl-ether)-N,N,N'-tetraacetic acid (EGTA), spermine and--to a lesser extent--spermidine and Hoechst 33,258 inhibited spontaneous DNA fragmentation. Under the same conditions chromatin condensation, as assessed by nucleoid sedimentation, increased. Exposure of chicken embryo cells to various genotoxic agents, i.e. doxorubicin, bleomycin, methyl methanesulfonate, thiyl radicals, H2O2, UV light, and X-rays, increased DNA fragmentation in a dose dependent manner. Zn2+ or EGTA diminished DNA fragmentation in cells exposed to bleomycin, thiyl radicals, H2O2 and UV light. An apparent sensitisation to X-irradiation has been observed in Zn2+ or EGTA-pretreated cells. It is suggested by the present investigations that, with agent specific peculiarities, apoptotic phenomena are implicated when nucleotoxicity is assessed in chicken embryo cells by physico-chemical short-term tests in vitro.