Cadmium uptake, storage and metabolism was studied in the whole soft t
issues, digestive gland and gills of the bivalve Ruditapes (Venerupis)
decussata. Accumulation of cadmium was linear with time in the whole
soft tissues. Much of the metal occurred in the cytosol, bound to meta
llothionein, and this also increased with time of exposure. Measuremen
ts of metallothionein, by differential pulse polarography, showed that
in controls and clams exposed to cadmium (400 mu g 1(-l)) concentrati
ons of the protein were present according to the sequence: digestive g
land> gills> remaining tissues. When clams were exposed to sublethal c
admium concentrations, metallothionein concentrations measured in the
heat-treated cytosolic extracts of the whole soft tissues increased by
small but significant amounts. Increases in metallothionein concentra
tions were also observed in the digestive gland and, most notably, in
gills. X-ray microanalysis of gills and digestive gland revealed that
cadmium was not accumulated within structured lysosomes, mitochondria
or other cell organelles. The low levels of significant de novo synthe
sis of metallothionein in response to cadmium exposure in the whole so
ft tissues and digestive gland of R. decussata reduce the value of the
se tissue preparations as a means of detecting sublethal responses to
metals: gills appear to be a more suitable tissue for detecting such r
esponses.