Degradation of hepatic zinc-thionein after parenteral zinc administration

Abstract

A low-molecular-weight protein, zinc-thionein, a metallothionein, was implicated as having a regulatory function in zinc metabolism. The half-life (t_1/2) of hepatic zinc-thionein was determined by pulse-labelling with either L-[³⁵S] cystine and/or ⁶⁵Zn. In two experiments with L-[³⁵S]cystine, the t_1/2 of zinc-thionein was 18h and 19h. Most of the soluble ³⁵S-labelled hepatic proteins had a t_1/2 of 4 days. The t_1/2 of zinc-thionein calculated by using ⁶⁵Zn was 20h. The close similarity between the calculated and measured t 1/2 values for zinc-thionein suggests that release of Zn²⁺ from zinc-thionein probably occurs simultaneously with degradation of the protein moiety.