Metallothionein: Potential biomarker for monitoring heavy metal pollution in fish around Hong Kong

Metallothioneins (MTs) are a family of low-molecular-weight, cysteine-rich proteins that have a high affinity for divalent ions. Recently, MT level has become a major biomarker for monitoring metal pollution in fish. As a first step towards the development of a reliable and standard assay method for the detection of fish MTs in Hong Kong waters, reverse transcription-polymerase chain reaction (RT-PCR) was employed to obtain complementary DNAs (cDNA) coding for goldfish (Carrasius auratus) and tilapia (Tilapia mossambica) MTs. Based on the cloned tilapia MT cDNA sequence, specific primers were designed to detect MT mRNA levels in tilapia tissues using RT-PCR, Screening of a common carp liver cDNA library also yielded MT cDNAs. For the development of an immune-assay for monitoring MT levels in fish tissues, synthetic peptide, made according to the conserved teleost MT N-terminal amino acid sequences, was employed to raise anti-fish MT antibodies, These molecular and immunological probes will be useful in 1. testing the feasibility of using tilapia MT levels as a biomarker for monitoring metal pollution in Hong Kong fish and 2. determining the basic physiological significance of MT in metal tolerance in tilapia.