QUANTITATION OF METALLOTHIONEIN MESSENGER-RNA BY RT-PCR AND CHEMILUMINESCENCE

A general procedure has been developed for the determination of mRNA expression by reverse transcription polymerase chain reaction (RT-PCR), over a wide concentration range, with quick quantitation of amplified products by luminescence. The discriminating power of this approach is the specific hybridization of PCR product to ruthenium-labeled oligonucleotide probe(s). This method is sensitive enough to detect increases in the formation of PCR product by the 6th cycle. The accumulation of PCR product was successfully modeled with a recursive relationship. This procedure was capable of accurately determining starting template copies over a 9-log dynamic range, with a sensitivity limit of 10(2) copies. Inclusion of an mRNA internal standard (identical to amplified template except for a 6-bp deletion) corrected variabilities in the reverse transcriptase as well as PCR, allowing for the expression of data as mRNA copy number/mu g total tissue RNA. This procedure was used to detect changes in levels of winter flounder (Pleuronectes americanus) liver metallothionein mRNA. Liver metallothionein mRNA levels ranged from 1.0 x 10(6) copies/mu g total tissue RNA in control samples to 1.0 x 10(9) copies/mu g total tissue RNA in samples treated with Cd (a known metallothionein mRNA inducer).