Studies on the uptake of cadmium by the crab Carcinus maenas in the laboratory. II. Preliminary investigation of cadmium-binding proteins

Abstract

All internally distributed water-soluble cadmium absorbed by the crab Carcinus maenas (L.), either from solution or from a food source, is associated with protein. Watersoluble extracts of the midgut gland, muscle, gill and remaining internal body tissues (the “rest”) have been separated chromatographically and the absorbed cadmium contents of separate protein fractions measured. In the midgut gland, “rest” and gill, cadmium is associated with protein of high (>50,000) and low(<6,000) molecular weight in proportion to the amount of protein present. In the muscle, cadmium is bound to high but not to low molecular weight proteins. In addition, two proteins with a high affinity for cadmium have been found with molecular weights of approximately 12,000 and 27,000. The larger cadmium-binding protein is found in the midgut gland and “rest” (probably the haemolymph), the smaller protein in the midgut gland, “rest” and muscle. A tentative model of the fate of water-soluble cadmium absorbed by the crab is proposed.