Metallothionein-like proteins in Macoma balthica: effects of metal exposure and natural factors

Biological processes involved in the tolerance acquired by populations chro nically exposed to metal pollution in the environment were examined in balt ic clams (Macoma balthica) originating from both industrialized and clean a reas and in clams exposed experimentally to metals. It has been shown previ ously that clams surviving Ag and Hg exposure at LT50 did not protect thems elves by accumulating smaller amounts of metals than clams that failed to s urvive, so attention was focussed on the physicochemical forms of storage o f the accumulated metals. Silver was found to be predominantly bound to ins oluble forms and Cd and Hg to soluble forms. In both controls and contamina ted clams, a metallothionein-like protein (MTLP) has been shown to be prese nt, the concentrations of which did not depend on the geographical origin o f the clams. The significant relationship between metal and MTLP concentrat ions shown in the baltic clams suggests that the induction of this protein could provide a useful tool for the biomonitoring of metal pollution. The i nfluence of natural factors (season, weight), however, must be taken into a ccount when interpreting such data.