CADMIUM AND METALLOTHIONEIN TURNOVER IN DIFFERENT TISSUES OF THE GASTROPOD LITTORINA-LITTOREA

This paper attempts to link the kinetics of Cd and metallothionein tur nover in the intertidal marine snail Littorina littorea. The results d emonstrate that the turnover of metallothionein is tissue dependent. M etallothionein has an estimated half-life of 69 and 160 days in the gi lls and kidney, respectively. The half-life could not be calculated fo r metallothionein in the digestive gland and is probably much longer t han the other two tissues. Cadmium elimination from the gill and kidne y is considerably slower than the respective metallothioneins (half-li fe in excess of 300 days) indicating closed cycling of the metal in th ese tissues. In contrast, cadmium levels in the digestive gland contin ue to increase during the detoxification period reflecting some remobi lization from other tissues, Metallothionein turnover is extremely slo w in Littorina when compared with mammals and other bivalve molluscs: even though metallothionein degradation is measurable in some gastropo d tissues, the released cadmium may induce de novo metallothionein syn thesis to which cadmium becomes resequestered. The stow metallothionei n turnover rates and the lack of significant cadmium excretion testify to the relatively stable nature of the cadmium-metallothionein comple x in this invertebrate. (C) 1998 Elsevier Science B.V. All rights rese rved.