Joint International Conference on Long-term Experiments ...

DETERMINATION OF METALLOTHIONEIN, CADMIUM, COPPER AND ZINC
LEVELS IN HUMAN AND RAT TISSUES
Camelia Bara
University of Oradea, Faculty of Environmental Protection, Oradea
26, General Magheru Street, Oradea
ABSTRACT
Metallothionein (MT), zinc (Zn), copper (Cu) and cadmium (Cd) were determined in 10
tissues (brain, heart, kidney cortex, liver, lung, muscle, pancreas, small intestine, spleen and
stomach) from human autopsies (10 male individuals, mean age 43 ± 9 years, all smokers)
and Wistar rats. The mean tissue concentrations of MT in the human samples varied
between 3.8 and 495 µg/g wet weight in spleen and kidney cortex, respectively. In most
tissues human MT levels were high as compared to rats; particularly in liver and kidney
cortex human MT levels exceeded those of rats about 25- and 10-fold, respectively. Positive
linear relationships were observed between Zn or Cu and MT in human liver and between
Cd and MT in human kidney cortex.
INTRODUCTION
Metallothionein (MT), a low molecular weight protein with high cysteine and metal content,
binds both essential (Zn, Cu) and non-essential metals (Cd, Hg). In view of the ability of
MT to be induced by metals, the protein plays a crucial role in the homeostasis and toxicity
of metals. The biological activity of metals thus is determined by both the concentration in
the tissue and the fraction bound to MT. However, there are few reports as to the MT
concentrations in human tissues. In a previous study we found high MT levels in human
kidney cortex, which were even higher in smokers. In these kidney cortices the amount of
cadmium bound to MT directly correlated with the content of renal cadmium but not with
zinc or copper. In a study, Onosaka et al. reported similarly high MT levels in human liver
and a strong positive relationship between hepatic Zn and MT concentrations.
To further elucidate the relationship between tissue levels of MT and metals, we
investigated in this study the levels of MT, zinc, copper and cadmium in 10 different organs
from human autopsies and rats. Some of the rat data have been previously reported.
MATERIALS AND METHODS
Samples of human tissues were obtained from 10 male individuals (20-50 years old, mean
age 43 ± 9, all smokers) necropsied within 2 days after sudden death. None of the
individuals received medication before death. Samples were stored at -80°C until being
processed further. Tissues of humans and rats (Wistar strain, males, 180-200 g) were
homogenized with a Potter-Elvehjem or Ultra-Turrax in 4 or 9 vols, of 30 mM Tris-HCl
buffer pH 7.4, and subsequently centrifuged at 18 000 x g. MT was determined in the
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