engleski

Metallothionein mediated tolerance in developing, metal-exposed embryo of Mytilus galloprovincialis

Early developmental forms of marine bivalves, including Mytilus are often used for toxicological testing in order to assess water quality criteria in controls of the marine environment. In this short communication our previously published results were summarized (Pavičić et al., 1994 a and b) dealing with effects of selected metal ions (Zn, Cd and Hg)on formation of the straight-hinge (D-veliger)larvae 48 hours postfertilisation. Complementary studies conducted on embryo-larval toxicity and on determination of the metallothionein (MT) level may contribute to the better understanding of a metal tolerance during early development of bivalve molluscs. It has been found that both, a constitutive level of MT and metal-induced expression of MT were metal- and stage-specific. The particularly intriguing phenomenon observed was the less than additive effect of Zn and Cd when applied simultaneously to the sea water, showing a significantly higher proportion of normally formed D-veligers, smaller reduction of their primary shell length as well as the markedly higher level of MT in comparison to the sum of corresponding single-metal effects. The recently proposed concept on metal intoxication and MT-mediated tolerance in marine invertebrates (Roesijadi, 1996), based on the model of Palmiter (1994), deals with metal-induced MT gene expression mediated by zinc-sensitive inhibitor of transcription factor MTF-1 in mice. Consecutively, the Zn and Cd antagonistic effect observed in developing ambryos of M. galloprovincialis may be considered as a consequence of MT reinduction by Cd-Zn replacement reaction in previously induced Zn-MT. References R.D.Palmiter, Proc.Natl.Acad.Sci., USA 91(1994) 1219-1223. J.Pavičić, M.Škreblin, I.Kregar, M.Tušek-Žnidarič, P.Stegnar, Comp.Biochem.Physiol. 107C (1994) 249-257. J.Pavičić, B.Smodiš, M.Škreblin, I.Kregar, P.Stegnar, Comp.Biochem.Physiol. 109C (1994) 37-46. G.Roesijadi, Comp.Biochem.Physiol. 113C (1996) 117-123.

metallothionein level; embryo-larval toxicity of metals

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