The objectives of this investigation were to study the role of
zinc-thionein in the metabolism of excessive amounts of
zinc and the re-utilization of
zinc bound to this
protein. Rats were injected ip with 5 mg Zn/kg
body weight as
zinc chloride for 5 days to induce the synthesis of
zinc-thionein.
Proteins with molecular weight of 10,000 with high affinity for
zinc were synthesized in rat liver and intestine. These
proteins were heat stable. Large scale isolation of this
protein from rat liver was achieved by a simple method consisting of a heating step and
sephadex gel fractionation.
Intravenous injection of isolated 65Zn-thionein to rats resulted in similar organ distribution of
zinc as that after 65ZnCL2 injection. Gel filtration experiments with liver supernatant from rats injected with 65Zn-thionein showed that a major portion of 65Zn was transfered to other
protein fractions and was re-ultilized similar to inorganic
salts of
zinc. Morphological studies showed no toxic effects after injection of
zinc-thionein. These results show that
zinc-thionein is metabolically active and non-toxic.