Evaluation of metallothionein induction as a biological marker of environmental pollution

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In this research project, I have studied on (1) the development of enzyme-linked immunosorbent assay (ELISA) system for mammalian metallothioneins (MT), (2) the establishment of ELISA system specific to fish MT,and (3) the assessment of MT kinetics in crucian carps induced by environmental factors.(1) Because of its weak immunogenicity, there has been no useful ELISA system available for the determination of fish MT.First, I have developed a sensitive ELISA system by producing antibodies against rat MTs, horse MTs, and homologous N-terminal peptide. The proposed competitive ELISA was constructed using guinea pig antiserum specific to horse MT-I,being highly sensitive with the lowest measurable limit of 3 ng/ml. This ELISA system made it possible to evaluate the relation between heavy metal toxicity and MT induction in rat intestinal epithelial cell line, IEC-6 cells. However, this method was not available for determination of fish MT.(2) From the liver of crucian carp injected with cad … More mium chloride, 2 isoforms of cadmium-bound MT,I and II,were purified to the homogeneous state. Although the antiserum raised against crucian carp MT-II had little cross-reactivity with crucian carp MT-I,Crucian carp MT-II-specific ELISA system established was as sensistive as that for mammalian MTs. In the future, this assay system should be applied to analyze the MT levels in crucian carps living in the river and lake.(3) The induction profiles of tissue MT were assessed in crucian carps exposed to cadmium (1 mg/liter) in their aquarium water. MT was efficiently induced in the liver and kidney in response to cadmium, followed by the significant induction in the intestine. Such a tissue-specific induction of MT closely related to the distribution profile of cadmium. Cadmium and zinc predominantly induced MT-II in the fish liver, while dexamethasone and stress (vigorous airation) induced both isoforms. From these results, I conclude that the elevated levels of crucian carp MT is a useful biological marker for environmental pollution. Less