A thesis submitted in partial fulfillment of the requirements for degree of Master of Science. Inter-university Program on Environmental Toxicology, Technology and Management, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 2001

The effect of cadmium exposure on the metallothionein (MT) induction in Tilapia fish has been studied. The aim of this study was to evaluate the effect of cadmium exposure on the MT induction and lipid peroxidation production in Tilapia in an attempt to evaluate the potential usefulness of the two parameters as biomarker of exposure and biomarker of effect, respectively. The preliminary study was performed to find the appropriate range of cadmium concentrations for exposure to the fish. The research was divided into two studies, dose-response relationship and time-course study, which were conducted simultaneously. Then the effects of cadmium exposure on metallothionein induction and on lipid peroxidation were conducted in the short-te1m and long-term period. Experimentally, fish were exposed to various levels of cadmium over a short-term period of up to seven days or over a long-term period of up to fom weeks. The levels of cadmium accumulated, metallothionein expression, malondialydehyde production which indicates lipid peroxidation were monitored. Cadmium accumulation in fish liver was concentration and time dependent during the short-term and long-term period as well, particularly at high level of concentrations, between 0.50-ppm, and 1.00-ppm. MT mRNA expression appeared at the seventh day after exposure and showed concentration dependence to the cadmium concentration in water. During the long-term period MT mRNA expression in fish liver were concentration dependent, but not time dependent. The MT mRNA expression was linearly co1Telated to cadmium accumulation in fish liver during the short-term period, but not in the long-te1m. In the short-term period, MDA production was dependent on cadmium accumulation in fish liver, but not in long-term period. In the short-term period, MDA production increased proportionally with time and concentration of cadmium. The highest MDA level was reached in the 1.00-ppm concentration level at the seventh day. But during the long-term study the MDA productions varied. Cadmium accumulation in fish liver correlated with MDA production in this organ during the short-term period. But during the longterm period the coITelation decreased. A positive coITelation was observed between MT mRNA expression and MDA production in the liver during the short-term period, but not in the longterm study.