Determination of metallothionein-3 by a competitive enzyme-linked immunosorbent assay in experimental animals.

An easy and specific enzyme-linked immunoassay (ELISA) for the determination of metallothinein-3 (MT-3) in experimental animals for the research of heavy metal and chemical toxicity has not been reported yet. Therefore, we have developed a competitive ELISA, using a specific monoclonal antibody raised against human recombinant MT-3 (rMT-3). The epitope mapping of the antibody was conducted using mouse, rat, and human MT-3s and peptide fragments of human MT-3. MT-1/2, MT-3 knock-out (KO) mice and human brain and liver were used for the evaluation of the ELISA. A pretreatment method of the tissue homogenates was also examined. The antibody used for the ELISA had the same cross-reactivity with MT-3 in humans and experimental animals. The human MT- 3 NH(2) terminal peptide (Fr. 1-17) was the demonstrated epitope of this antibody. The reactivity of this ELISA in brain homogenate of MT-3 KO mouse was significantly low compared with the wild type and MT-1/2 KO mice. The lowest detection limit of the ELISA was 10 ng/ml and over 80% of the spiked rMT-3 was recovered in the brain homogenate. The assay linearity was intact with a 5-fold dilution in the brain homogenate. The inter- and intra-assay CV was 6.5%, respectively. An effective pretreatment procedure of the tissue homogenate was also established for this MT-3 ELISA. In conclusion, this competitive ELISA is an easy and specific method for measuring the brain MT-3 level in experimental animals.