Metal Toxicity and Metallothionein mRNA Induction in a Rat Intestinal Cell Line

Abstract

Our aim was to characterise a rat intestinal cell line, IEC-17, isolated by Quaroni from neonatal rat duodenum, as an in vitro model for the study of metal metabolism and toxicity. Dose-effect experiments were carried out using two essential trace elements (zinc and copper) and one toxic metal (cadmium). The results showed different trends of responses between physiological and toxic metals; the LD50 values were 250μM for Zn, 600μM for Cu, and 5μM for Cd. Since metallothioneins are the only identified and characterised proteins involved in metal detoxification, we tried to establish a relationship between metallothionein gene expression and resistance to metal toxicity. Metallothionein in mRNA induction was studied by the Northern blot technique, using an MT-1 cDNA probe. A basal level of metallothionein mRNA was detectable in cells growing in normal medium. Induction by Cd of metallothionein mRNA was very strong after 6 hours. Both Zn and Cu were also able to induce MT mRNA after 6 hours in IEC-17 cells in a dose-dependent manner.