METALLOTHIONEIN-LIKE METALLOPROTEINS IN THE BALTIC CLAM MACOMA-BALTHICA - SEASONAL-VARIATIONS AND INDUCTION UPON METAL EXPOSURE

Metallothionein-like proteins (MTLs) have been measured by differentia l pulse polarography every two months during a period of two and half years in the marine bivalve Macoma balthica from two locations of the Western Scheldt Estuary. The MTL concentrations (0.85 to 7.81 mg g(-1) dry wt) are comparable to most values found for other marine inverteb rates. These concentrations vary significantly with the seasons (highe r in winter, lower in summer), which is mainly due to body weight fluc tuations. Strong correlations exist between MTL and metal levels. Upon short-term exposure to a mixture of Cd, Cu and Zn, there are on avera ge significant MTL increases, but important seasonal variations have b een observed: in winter, the clams are more sensitive to metals, uptak e more Cd and Cu and induce more MTL than during the warmer months.