1999 Volume 16 Pages 25-32
Cadmium (Cd) is a toxic heavy metal which causes cell impairment at higher concentration and acts as endocrine disruptor at extremely low concentration which may cause adverse effect against ecological systems involving humans. Studying toxic effect of heavy metals from the aspect of the cellular function by using a single cell eukaryotic protist Euglena gracilis, we revealed that an inorganic form Cd, CdCl2 caused abnormal cell division at the ppb level that used to be regarded as safe level. In the present study, Euglena gracilis Z grown in the Koren-Butner(KH) medium for 6 days at 28°C under 2,800 lx light/dark cycle with every 12 hours interval was used as a biomarker organism. To the Euglena cells of 104 cell/ml in the Zn-deficient KH medium CdCl2 as 200ppb to 20ppm was added, and cultured for 2 to 7 days under the same condition as above. The occurrence of teratogenic cell division was checked under Allen’s video-enhanced contrast microscopy ARGUS-100. The effect of Zn addition on the prevention of CdCl2-induced teratogenicity was examined with addition of ZnSO4 from 1 to 200ppm by keeping CdCl2 at 10ppm. Exposure of CdCl2 on the Euglena gracilis Z cells caused abnormal cell proliferation under the Zn-deficient Koren-Butner medium. More abnormal cell proliferation was observed at ppb level rather than at ppm level. As far as incubating the cells in the presence of CdCl2 suppression of the outbreak of abnormal cell proliferation could not be accomplished even by the addition of Zn as 10 times as much molar as Cd.
