Temporal variations in metallothionein concentration and subcellular distribution of metals in gills and digestive glands of the oyster Crassostrea angulata

Abstract

The metallothionein levels and metal concentrations in whole body, digestive gland and gills of Crassostrea angulata were analyzed in field samples collected from the River Guadalquivir estuary over several years following a mining waste spill upstream. The subcellular distribution of metals was analyzed to determine the mechanisms involved in the detoxification process. The highest metallothionein levels were reported in the digestive gland shortly after the mining contamination event. In this organ, metals are stored preferentially in the non-cytosolic fraction when increased bioaccumulation takes place. In the cytosol of the gills, metals are associated with metallothionein, whereas in the digestive gland, the distribution of metals between metallothioneins and high molecular weight proteins is similar. Metallothionein variation cannot be explained by metals alone; other abiotic factors must be taken into account. In order to use metallothionein as a metal exposure biomarker in field studies, natural variability needs to be taken into account for the correct interpretation of results.