Changes in brain metallothionen and zinc during development in transgenic mice

The developmental alterations in metallothionein (MT) proteins and zinc (Zn) were investigated in brains of two transgenic strains of mice. MT protein was measured by a cadmium binding assay and Zn by atomic absorption spectrophotometry. MT proteins were expressed at birth (day 1) both in MT-I overexpressing transgenic mouse (MT-I*) and MT-null (expressing only brain specific isoform, MT-III) transgenic mouse. MT proteins level (mainly MT-I) in MT-I* was 16.1 microg/g at birth, and thereafter increased with age to a maximal adult level of 55.3 microg/g (day 60). Zn level in MT-I* also increased from 8.43 microg/g (day 1) to 20.7 microg/g (day 60) with age. MT protein (MT-III) in MT-null mouse was 9.71 microg/g at birth and remained relatively unchanged during development. Zn level in MT-null mouse at birth was 9.46 microg/g and also remained unchanged during development. The similar alterations in MT isoforms and Zn in brain during development suggest that MT isoforms may act as a Zn binding protein.