Uptake and Efflux of Cd and Zn by the Green Mussel Perna viridis after Metal Preexposure

Abstract

Cadmium and zinc uptake from the dissolved phase, assimilation efficiency from the dietary phase, efflux rate constants, and body burden as well as clearance rate were measured in the green mussel Perna viridis with or without laboratory preexposure to Cd or Zn. Efflux rate constants and clearance rates were little affected by preexposure to either Cd or Zn. In contrast, the assimilation of Cd increased by 1.2-1.6 in mussels preexposed to Cd (subsequent Cd concentrations 10.2-25.9 microg(-1)) as compared to controls (0.19-0.39 microg g(-1)). This increase corresponded to an elevation in the proportion of Cd associated with the metallothionein-like proteins (MTLPs) in the mussels, suggesting that exposure to Cd and subsequent induction of MTLPs affected Cd accumulation. Exposure to Zn only resulted in elevated body concentrations following 7-d exposure to 250 microg L(-1), although Zn and Cd uptake from the dissolved phase were reduced by 24-47% by exposure to a lower concentration (100 microg L(-1)) for 7 and 21 d. Despite the lack of an increase in body Zn concentration, the subcellular distribution was altered such that the proportion of Zn associated with the metal-rich granules increased. This study indicates the importance of the subcellular distribution of metals in affecting the biokinetics and thus the toxic effects of metals on aquatic animals. Cd preexposure has potential effects on its influx from the dietary phase, e.g., increasing the importance of dietary uptake and further increasing the body burdens. In contrast, preexposure to Zn has a negative effect on Cd and Zn influx from the dissolved phase, suggesting the mechanism of Zn regulation but also potentially reducing Cd uptake and body concentrations over the long-term exposure. Such effects may have implications for biomonitoring studies involving a single species that modifies physiological processes affecting metal uptake (and hence bioavailability). Caution is needed in extrapolating data to species not capable of making such changes, particularly for Cd, which is not regulated and for which the effects of an elevated body burden are most obvious.

Subcellular controls of silver biokinetics in the green mussel Perna viridis from two hydrographic zones

“…Tissue Ag concentration and subcellular Ag distribution. Total tissue Ag concentrations in the green mussels were analysed in 5 individuals from each site, using previously described methods (Blackmore & Wang 2002, Ng & Wang 2004. The soft tissue of the mussels was acid-digested, and the digests were analysed by inductively coupled plasma-mass spectroscopy (ICP-MS, Perkin-Elmer, Elan 6000).…”

“…The clearance rate was used to compare any physiological difference in pumping activities between the 2 populations of mussels, and was quantified using a wellestablished method (Blackmore & Wang 2002, Shi et al 2003). The clearance rates of 8 individuals were determined, and the rate of each individual was calculated from the mean of 2 consecutive measurements (0 to 20 and 20 to 40 min).…”

Expression of cytoprotective proteins, heat shock protein 70and metallothioneins, in tissues ofOstrea edulis exposed to heat andheavy metals

“…This could be ascribed to a lower water-filtering rate by the animal exposed to such high amounts of contaminants; however, an interaction between the metals or a competition during their cellular uptake could be another possible explanation for the reduced effect of Cd. In Perna viridis, for example, the preexposure to Zn has a negative effect on Cd assimilation and potentially reduces Cd uptake (Blackmore and Wang 2002); Meshitsuka et al (1987) reported that cadmium uptake is inhibited by Cu(II) and affected by Zn(II) in cultured cells.…”

Environmental concentrations and bioaccumulations of cadmium and zinc in coastal watersheds along the Chinese Northern Bohai and Yellow Seas

“…A strong positive association between concentrations of Zn and Cd in crabs implied that the Cd and Zn originated from a common source. Blackmore and Wang (2002) found the same results in green mussels [39]. Positive relationships between the Cd and Zn in water and sediment implied that Cd and Zn had common sources in water and sediment.…”