The basis for increased metallothionein in a natural population of Crassostrea virginica

Abstract

Metallothionein (MT) is elevated in a natural population of the oyster Crassostrea virginica that is exposed to cadmium. However, induction of MT is not a likely cause for this elevation. This was concluded after re-examination of the results of a study in which MT mRNA and MT s were analysed in oysters collected from a cadmium-contaminated environment. MT mRNA concentrations did not differ in oysters collected from a cadmium exposure gradient and could not account for increases in MT, although laboratory experiments had clearly shown that induction of MT in response to cadmium is seen at both transcriptional and translational levels. It appears that, at the low concentrations of cadmium encountered in natural environments even when contaminated, the underlying basis for the elevation of MT is its stabilization by cadmium and its accretion while being synthesized at basal rates, rather than induction of MT per se. This observation has implications for the efficacy of using either MT mRNA or MT levels in molluscs in assessing metal exposure or its biological effects in contaminated natural environments.

Keywords::

• Metallothionein;Mollusc;Oyster;Cadmium;Metal