Expression characteristics of potential biomarker genes in Tra catfish, Pangasianodon hypophthalmus, exposed to trichlorfon.

Trichlorfon (TRC) is the most common organophosphorous insecticide used in aquaculture practices in Southeast Asian countries. Indiscriminate use of TRC can either damage or alter the enzymatic and hormonal activities in the living organisms. In this present study, therefore, toxicogenomic analyses using real time PCR was used to characterize expression levels of various genes in Pangasianodon hypophthalmus after exposure to three concentrations, the 96 h 1/100LC(50) (0.01 mg/L), the 96 h 110LC(50) (0.1 mg/L) and the 96 h 12LC(50) (0.5 mg/L) of TRC for 6 h, 24 h, 96 h, 7 days, 14 days, 28 days and 56 days respectively. The expression kinetics of stress and other cellular toxicity representative genes such as heat shock protein70 (HSP70), growth hormone, acetylcholinesterase (AChE), trypsinogen, cytochrome P4501B (CYP1B) and cytochrome oxidase subunit 1 (COI) were investigated in liver and gills. TRC at a level of 0.1 mg/L and 0.5 mg/L induced a time and dose-dependent increase in the expression of the HSP70, COI and CYPIB while the transcript level of AChE, growth hormone and trypsinogen were significantly down-regulated. These results could permit to develop a "molecular biomarker system" which can be applied as a first-tier method of identifying contaminant exposure before effects at population level occur.