Trace metal and major ion interactions in aquatic animals

In reviewing studies of trace metal uptake over the last 30 years, evidence is sought for specific mechanisms controlling transepithelial metal uptake or loss, and their possible relationship with pumps controlling the regulation of physiologically-important electroytes. There is evidence of zinc regulation in some crustaceans. However, the widespread occurrence of specific transepithelial regulatory mechanisms for trace metals is unlikely. Metal uptake and toxicity is often negatively associated with salinity. Although this phenomenon is probably related, in part, to trace metal speciation, an associated calcium effect is seen in some species. Several examples exist of interactions between calcium regulation and trace metals, suggesting there may be a number of shared pathways. Cadmium is particularly implicated in this regard. Inhibition of Na/K ATPase by trace metals is seen in some fish, although there is no direct evidence of competitive inhibition of transepithelial sodium movement by trace metals.