Changes in zinc and copper homeostasis in human livers and kidneys associated with exposure to environmental cadmium

This study was undertaken to assess changes in zinc and copper homeostasis in human tissues that could be attributed to human exposure to environmenta l cadmium, using samples of lung, liver and kidney cortex of 61 Queensland residents, aged 2 to 89 years, who had died of accidental causes. None of t he subjects were exposed to cadmium in the workplace. Levels of zinc in liv er and kidney cortex samples showed inverse associations with donor age whe reas zinc in lung only showed inverse association with gender. Lung zinc le vels in females were 14% lower than in males. Zinc in liver and kidney cort ex samples were found to exist in at least two pools; one was associated wi th cadmium that bound to metallothionein (MT) and the other was associated with non - MTbound copper. In liver, the amounts of zinc in the MT pool wer e smaller compared to those in non-MT pool given that only 7% of zinc varia tions were explained by cadmium whereas 22% of the liver zinc Variations we re accounted for by non - MT bound copper. In sharp contrast, larger amount s of zinc in kidney cortex samples were in the MT pool, compared to those i n the non-MT pool given that cadmium was found to explain 69% of total zinc variation whereas copper explained only 17% of kidney zinc variations. The levels of copper in liver were found to be increased by 45-50% in subjects with high cadmium exposure level, compared to subjects of similar ages wit h medium exposure level. The levels of zinc and copper in kidney cortex sam ples in the subjects with high cadmium exposure were both found to be signi ficantly elevated compared to those found in the medium-exposure group wher eas copper contents were about 19-23% greater than in medium- as well as lo w-exposure groups. Taken together these results indicate increased sequestr ation of zinc and copper in liver and kidney cortex samples. The increases in metal sequestrations were observed in liver samples having cadmium conte nts of greater than 1 mug/g wet weight and in kidney cortex having cadmium contents of greater than 26 mug/g wet weight. Zinc and copper contents in l ung of this sample group, however, were not associated with cadmium due pro bably to lower exposure levels compared to those of liver and kidney.