Metallothionein gene expression in zebrafish embryo-larvae and ZFL cell-line exposed to heavy metal ions.

The aim of this study is to investigate the induction of zebrafish metallothionein (zMT) gene expression following the administration of different metal ions using in vivo and in vitro models. The zebrafish embryo-larvae were used for the in vivo study, and MT gene expression was studied during the development from fertilization (8hpf) to embryo-larval stage using real-time PCR. The LC50 values and zMT mRNA levels were also measured in embryo-larvae exposed to various metal ions. The general trend of 24 h LC50 values as determined is Cu2+ < Hg2+ < Cd2+ << Zn2+. However, Hg2+ was found to be the most potent metal inducer with the highest level of zMT mRNA induction (40-50 folds) in 8hpf embryo-larvae, followed by Cd2+ (approximately 20 folds); Cu2+ and Zn2+ only gave approximately 5 fold of induction. In the in vitro study of ZFL cell-line, Cd2+ is the most potent inducer of zMT mRNA (up to 250 folds), Cu2+ and Zn2+ gave similar potency of approximately 50-100 folds, and Hg2+ gave approximately 40-50 folds of zMT mRNA levels over the control group.