Cadmium accumulation and toxicity in the kidney of the bay scallop Argopecten irradians

Specimes of bay scallops, Argopecten irradians, collected from shallow-water eel-grass beds near Beaufort, North Carolina (USA) in September 1979, were exposed to 0.7 ppm cadmium in flowing seawater for 5 d. This exposure resulted in a massive extrusion of the calcified concretions of most of the kidney epithelial cells, although marked morphological damage consisting of cytoplasmc degeneration was apparent in only a few focal areas of the kidney. In addition, unique cytoplasmic membrane-bound bodies were observed in epithelial cells of cadmium-treated but not control scallop kidneys. In some cells, these bodies appeared to fuse with the main concretion vacuole. Kidneys of cadmium-treated scallops accumulated cadmium to 200 ppm on a wet wt basis; of this 60% was associated with concretions (2 000 ppm dry wt) and 38% with the membranous pellet obtained after ultracentrifugation at 105 000 g for 1 h. Approximately 2% of total kidney cadmium was associated with the cytosolic fractions but, unlike zinc or manganese, which were bound to either high or low molecular weight species, a large component of the cadmium in this fraction was bound to a protein peak of approximately 21 000 daltons. Results of this study indicate that kidney concretions of A. irradians play a major role in the control of renal cadmium accumulation and excretion and hence the toxicity of cadmium to this organism.