Quantitation of metallothionein isoforms in mouse liver on capillary zone electrophoresis

A method for determining concentration of metallothionein (MT) isoforms in mouse liver was established by using capillary zone electrophoresis (CZE), and carbonic anhydrase was used as an internal standard. The cytosol fraction was heated at 100 degrees C for 1 min, and the supernatant was applied directly to CZE after filtration. Both MT-1 and MT-2 isoforms were identified from the migration times of purified MT isoforms, and the peaks were definitely identified from the other peaks. In addition, carbonic anhydrase was adopted as an internal standard. Based on standard curves of purified MT isoforms, concentrations of MT isoforms in the liver were determined from the estimates of peak areas. In control mouse liver, MT-1 isoform was detected at 48.5+/-25.4 mu g/g wet weight, and MT-2 isoform was 154.0+/-39.7 mu g/g. Twenty-four hours after zinc injection, MT-1 increased to 773.7+/-374.3 mu g/g, and MT-2 was 487.2+/-207.1 mu g/g. The addition of ascorbic acid to the homogenizing medium resulted in the decrease of MT isoforms in mouse liver. From these findings, we concluded that CZE analysis using a polyacrylamide-coated tube at neutral pH makes quantitation of MT isoforms in mouse liver possible. (C) 1998 Elsevier Science B.V. All rights reserved.