Cadmium and zinc kinetics in fish: studies on water-borne 109Cd and 65Zn turnover and intracellular distribution in minnows, Phoxinus phoxinus.

This study investigates the short- and long-term turnover of zinc and cadmium in fish. Juvenile minnows, Phoxinus phoxinus, were exposed to water-borne 109Cd and 65Zn for 24 hr. Tracer uptake, redistribution, elimination, and intracellular tracer distribution were studied for 60 days in tracer-free water. The influx of 65Zn from the water to the internal organs was more rapid than the influx of 109Cd, and the 65Zn turnover in the liver and kidney was considerably faster than the turnover of 109Cd. Moreover, in the gills and kidney, intracellular 65Zn was more mobile between intracellular compartments than 109Cd. The liver and kidney accumulated the major part of the 109Cd originating from the gills, whereas the head and skin, and muscle and bone-fractions retained the majority of the 65Zn. This indicates that the metals have different pathways in the fish body, after entering the body from the water. The cadmium levels in the gills, liver and kidney increased drastically because of the cadmium exposure, but the zinc levels in the organs were not markedly affected by a fifteen-fold increase in external zinc concentration, indicating a homeostatic control of zinc in the minnow.