Evaluation of rodent peroxisome proliferators in two species of fish (rainbow trout; Salmo gairdneri and Japanese medaka; Oryzias latipes)

• Main Author: Scarano, Louis John
• Language: ENG
• Published: ScholarWorks@UMass Amherst 1992
• Subjects: Environmental science|Toxicology|Aquaculture|Fish production
• Online Access: https://scholarworks.umass.edu/dissertations/AAI9219493

Rainbow trout (Salmo gairdneri) and Japanese medaka (Oryzias latipes) were exposed to three or four compounds, respectively, which have been shown to cause peroxisome proliferation in rodents. Trout were injected (intraperitoneally) daily for two weeks to the following chemicals and doses; the dimethylamine salt of 2,4-dichlorophenoxyacetic acid (DMA of 2,4-D) at 0, 2.5, 5 and 10 mg/kg/d, trichloroethylene (TCE) at 0, 10, 50 and 100 mg/kg/d or gemfibrozil at 0, 46, 87 and 152 mg/kg/d. Japanese medaka were exposed to di (2-ethylhexyl) phthalate (DEHP), 2,4-D (DMA) or gemfibrozil in water for two weeks in a static renewal system. Nominal doses used were 0, 90, 180 and 360 ppb, 0, 50, 100 and 200 ppm and 0, 1.25, 2.5 and 5 ppm for DEHP, 2,4-D and gemfibrozil, respectively. Medaka were also exposed to TCE for 16 hours in a closed system at doses of 0, 25 and 50 ppm. Peroxisome proliferation was assessed by measuring fatty acyl-CoA oxidase (FAO) activity and relative percent increase in peroxisomal bifunctional enzyme (PBE); enzymes which are involved in peroxisomal beta-oxidation. In addition, changes in liver weight/body weight ratios were measured. Results indicate that a mild peroxisome proliferative response was observed in rainbow trout exposed to gemfibrozil (significant increase in FAO activity at all three dose levels and a significant increase in liver weight/body weight ratios at the highest dose level only). There was no difference between control and treated groups in the trout exposed to 2,4-D or TCE. In the medaka experiments, a marginal response was observed in the gemfibrozil experiment (significant increase in PBE at the highest dose level and a non-significant increase in FAO activity in the mid- and high-dose groups). There were no significant, treatment related differences between control and treated fish in the TCE, 2,4-D and DEHP medaka experiments. It was concluded that fish may not be a sensitive model to screen chemicals for their ability to induce peroxisome proliferation.