Cadmium-induced abnormality in strains of Euglena gracilis: morphological alteration and its prevention by zinc and cyanocobalamin

Euglena gracilis is susceptible to cadmium (Cd) at high concentrations. The re are no comparative data on cytotoxicity or abnormality of CdCl2 to E. gr acilis Z and its achlorophyllous mutant SMZ. The present study examined the cytotoxicity of CdCl2 under continual exposure at levels ranging from sub- ppm to ppm, and assessed the effects of zinc (Zn) or cyanocobalamin (VB,,) supplementation on the suppression of Cd-induced abnormal cell proliferatio n and hypertrophy. With Zn levels restricted to I ppm [as Zn++], cell growt h of both E. gracilis strains was reduced in proportion to Cd concentration . More abnormal cells (hypertrophied, V-shape and starfish-shape) were obse rved in both strains at sub-ppm levels of Cd. ZnSO4 supplementation from 2 to 63 ppm significantly suppressed the incidence of Cd-induced abnormality. However, a significant increase in abnormal cells was observed following Z n supplementation at levels of 125 and 250 ppm, which produced remarkable d ifferences in cell morphology. The incidence of abnormal cells varied with supplemented VB12 levels ranging from 4 to 250 ppb in both E. gracilis stra ins. (C) 2001 Elsevier Science Inc. All rights reserved.