EFFECTS OF CADMIUM LEVEL ON CHROMOSOMAL STRUCTURE OF SNAKEHEAD-FISH (Ophicephalus striatus) SARUNYA LAOVITTHAYANGGOON A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE (TOXICOLOGY) FACULTY OF GRADUATE STUDIES

The aim of this study is to determine the level of cadmium contamination in various organs of Snakehead-fish (Ophicephalus striatus). The detected levels of Cd were tested for genotoxic potential in snakehead-fish (SSN-1 cells) cell line by micronucleus assay. To evaluate the SSN-1 cells as a model for genotoxicity study, various concentrations of cadmium were applied to the cells, and the cadmium uptake levels and micronucleus frequencies were observed at various time intervals. The snakehead fish were collected from six different markets in Bangkok metropolitan: Bangkok noi, Ratchawat, Klongtaey, Yingchareon, Wongweanyai and Sainert markets. Cadmium residues were determined in various tissues of the fish by the Graphite Atomic Absorption Spectrophotometer (GFAAS). The results indicated varying accumulated cadmium levels in different parts of tissues. The levels found in muscles, skin, gills and livers were 0.02-0.11, 0.02-0.08, 0.02-0.08 and 0.13-1.68 ppm respectively. The highest level of Cd was 1.68 ppm (mg/kg.), which was found in the liver tissue of fish collected from Bangkok noi market. This level exceeded the acceptable standard level as determined by the Fish Inspection & Quality Control Division of Thailand, which is 1.5 ppm. Four concentrations of Cd (0.005, 0.05, 0.5 and 5 ppm) were applied to the cells for 24, 48 and 72 hours, then the cells were harvested and the frequencies of micronucleus occurred were determined. The results showed that three cadmium concentrations caused the significant increase in micronucleus frequencies that depended on dose, while the lowest tested concentration (0.005 ppm) caused no change on micronucleus frequency compared to relevant control cells. The micronucleus frequencies were compared with the levels of Cd uptake by the SSN-1 cells. Both micronucleus frequencies and cadmium uptakes depended on exposure levels. These results showed that the SSN-1 cell is a suitable model for in vitro genotoxic evaluation of cadmium and should be useful for genotoxicity screening of water pollutants. In addition, the contaminated levels in fish tissues can cause and alteration in chromosome structure; this may create a negative impact on frequent snakehead-fish consumers. More genotoxicity study of cadmium should be done.