On the proposed role of metallothionein in the transport of cadmium

In order to test a possible role of MT in the transport of Cd from liver to kidney, we compared the distribution of ¹⁰⁹Cd administered either in the form of CdCl₂ or CdMT. Unlike in earlier studies which employed relatively massive amounts of Cd, in the present studies a low total amount of Cd (15–30 μg) was continuously infused over a period of 2–3 days. Results confirmed a preferential renal accumulation of CdMT. High intracellular renal and hepatic MT concentrations, induced by repeated prior injections of Cd, Zn, or Hg, did not alter the tissue distribution of infused CdCl₂ or CdMT. It is interesting to note that in some further experiments, equivalent amounts of extracellular MT depressed renal uptake of CdMT. These findings are consistent with a role of MT in the transport of Cd from liver to kidney.