Relationship between shell weight and cadmium content in whole digestive gland of the Japanese scallop Patinopecten yessoensis (Jay).

Seasonal and age-specific variations of cadmium (Cd) concentration in the digestive gland were investigated in the Japanese scallop Patinopecten yessoensis from Peter the Great Bay, Sea of Japan, with different degrees of Cd pollution. The seasonal changes in Cd concentrations of the digestive gland were inversely proportional to the dry weight of the gland. Concentrations of Cd and total Cd content (mug Cd per organ) increased with age (age-specific) to the same extent in contaminated and uncontaminated areas. There was also a strong positive correlation between Cd content in the whole digestive gland and shell weight and it is proposed that this relationship can be used as a new criterion for comparative evaluation of Cd levels in scallops from different areas We hypothesize that Cd is uptaken into scallops in proportion to the amount of calcium that absorbed through ion channels, and in addition, Cd in the digestive gland is in immobile forms (e.g. metal-rich granules) that accumulate with age. Moderate environmental pollution has no effect on the relationship between Cd content and shell size and the observed decrease in growth performance of the scallops from polluted areas may be due to other factors.

An in vitro study of the effect of reactive oxygen species on subcellular distribution of deposited cadmium in digestive gland of mussel Crenomytilus grayanus.

The study was performed to assess in vitro effects of reactive oxygen species (ROS, oxyradicals) on intracellular distribution of accumulated cadmium in digestive gland of the mussel Crenomytilus grayanus. In vitro induction of ROS (by Fe/ascorbate reaction) in tissue homogenates of Cd-accumulated mussels led to a significant increase in lipid peroxidation (as conjugated dienes and malondialdehyde) and also to decrease in reduced glutathione and Cd-binding protein contents. Also fraction of MT-like proteins (20-22 kDa) has been shifted to a higher molecular weight area (40-45 kDa), which indicates dimerization of the protein. The level of intracellular vesicle-stored cadmium (within membrane compartments like lysosomes) was decreased significantly in oxyradicals-exposed tissue crude homogenate of mussels in comparison with controls. Additionally, Cd distribution among three weight classes of cytosol proteins has been significantly changed after ROS exposure. Taken together the results, there is a clear indication that ROS induce an oxidative stress resulting in damaging of intracellular Cd-binding compartments that may trigger (or contribute) the toxicity of this metal. Thus, from our experimental results and reviewed information follows that under high "pressure" of heavy metals on marine environment the aquatic organisms can show higher sensitivity to normal variations of natural factors of the environment or even decrease the range of tolerance to their variations.