Effect of heat treatment on metallothionein isoforms using capillary zone electrophoresis

The effect of heat treatment on metallothionein (MT) isoforms was observed by using capillary zone electrophoresis (CZE) at a neutral pH. Commercially available standard MT-1 preparation isolated from rabbit liver present as Cd and Zn mixed form was used as MT standard for the experiments in CZE. The MT-1 preparation was detected as two major peaks MT-1 and MT-2 identified from the migration times corresponded with those of purified isoforms and several minor peaks by CZE using a polyacrylamide-coated capillary at pH 7.4. The peak height of MT-1 of the standard MT-1 specimen decreased gradually from those of the non-heated specimen by heat treatment at 100°C until 4 min, but the peak of MT-2 did not decrease. In the cytosol fraction obtained from Zn-injected mouse liver, many peaks including MT-1 and MT-2 were detected in the specimen without heat treatment. The specimen heated at 100°C for 15 s had a stable baseline and the peaks of both MT-1 and MT-2 in cytosol fraction decreased gradually by heat treatment on time dependent manner. However, the ratio of peak heights of MT-1 and MT-2 did not change. From these results, the ratio of MT-1 and MT-2 in cytosol fraction is able to be observed well on CZE analysis after heat treatment.