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present findings on positive correlations between renal MT and cadmium, and hepatic MT
and zinc support this view.
Similarly, a close relationship between renal MT and tissue cadmium of smokers and
non-smokers and a positive correlation between MT and zinc in human liver have been
observed. These data indicate that MT in human kidney is mainly induced by cadmium
whereas in liver it may be preferentially induced by zinc and possibly copper. However,
since induction of MT has also been reported after various stresses, factors like the
hormonal and nutritional status and even the type of death might contribute as well.
There seems to be no correlation between hepatic and renal MT levels which we have
also observed in a recent investigation with 145 postmortem samples of liver and kidneys.
Except in 2 individuals, MT levels in human kidney cortex exceeded those of the liver.
However, in these cases hepatic Zn and renal Cd levels were more than twice and less than
50% of the average values, respectively. This supports the relevance for MT induction of the
high Cd content of the kidney as compared to the liver. In contrast, MT levels of rat liver
and kidney positively correlated with each other either after acute or subchronic exposure to
cadmium and zinc or the acute administration to iodoacetate. Therefore the chronic
exposure of man to low levels of metals, in particular cadmium, and the preferential
distribution of Cd-MT into the kidney may explain the observed lack of correlation.
In conclusion, these results demonstrate that considerable amounts of MT are present
in various human tissues. The particularly high levels of MT in human liver and kidney also
in comparison to rats and the high levels of metals in these tissues suggest that the
expression of MT in human tissues may respond to environmental factors, especially
chronic low-level exposure to metals.
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