Role of intestinal metallothionein in absorption and distribution of orally administered cadmium.

ABSTRACT

The effects of mucosal metallothionein (MT) preinduced by Zn on the intestinal absorption and tissue distribution of Cd were studied. 109CdCl2 was administered to control and Zn-pretreated rats. The total amount of Cd distributed to the liver and the kidney in the group pretreated with 100 mg/kg of Zn was about 70% that of the control group. In the control group, the Cd concentration in the intestinal mucosa reached a maximum 16-24 hr after its administration and then gradually decreased with time, unlike that in the liver and the kidney. The concentration of intestinal Cd in the pretreated group reached a maximum earlier than it did in the control group and most of the Cd was in the MT fraction. Pretreatment with Zn (100 mg/kg or higher, po) caused a reduction in the Cd concentration in the liver and an increase in the kidney. Pretreatment with Zn (5 X 10 mg/kg, sc) or Cd (5 mg/kg, po) also increased renal Cd concentration. This was effective at 24 hr but not at 0.5 hr after pretreatment. These effects of pretreatment with Zn (100 mg/kg, po) on tissue distribution of Cd were also observed after an intraintestinal injection of Cd but not after an iv injection. The results indicate that MT in intestinal mucosa plays a significant role not only in the absorption of Cd but also in its transport to the kidney.