Tissue-specific regulation of metallothionein and metallothionein mRNA accumulation in the Antarctic notothenioid, Notothenia coriiceps

The distribution of metallothionein and metallothionein mRNA was examined i n brain, liver and kidney of the red-blooded Antarctic fish Notothenia cori iceps. Basal levels of metallothionein were detected by silver saturation a ssay; the analysis showed large differences in the metallothionein content, with an increasing amount in kidney, liver and brain, respectively. Revers e transcriptase-mediated polymerase chain reaction was used to amplify two distinct metallothionein cDNA species from RNA extracted from the three tis sues examined. Northern blot analysis revealed a high constitutive expressi on of metallothionein mRNA in kidney, in spite of the low metallothionein c ontent found in this tissue. The analysis of the distribution of the two me tallothionein transcripts, termed MT-1 and MT-2, in the tissues showed that the MT-2 transcript was the major form of the metallothionein mRNA in kidn ey and brain, whilst in liver the expression levels of the two metallothion ein transcripts were comparable. This tissue-specific expression of isometa llothioneins in the Antarctic fish suggests the presence of an organ-specif ic regulation of the metallothionein genes.