Cadmium-induced DNA fragmentation is inhibitable by zinc in porcine kidney LLC-PK1 cells.

DNA fragmentation was induced by the addition of cadmium (10 microM) to cultured LLC-PK1 cells, resulting in cell death. The cells were able to survive exposures of 10 microM cadmium without change in morphology, but most had rounded by 40 microM. Other metals tested such as Cu2+, Co2+, Ni2+, and Pb2+ had much lower ability to induce DNA fragmentation in LLC-PK1 cells under the same conditions as used for cadmium, indicating that the fragmentation seen in kidney cells is cadmium-specific. DNA fragmentation induced by 10 microM cadmium was completely inhibited using an equimolar concentration of a cell-permeant chelator specific for heavy metals, N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine. Furthermore, the apoptotic mechanism evoked by 10 microM cadmium was blocked by 50 microM zinc which when used alone has no capacity for DNA fragmentation.