Hormetic response of cholinesterase from Daphnia magna in chronic exposure to triazophos and chlorpyrifos

• Published in: Journal of environmental sciences (China) 2011-01, Vol.23 (5), p.852-859
• Main Authors: Li, Shaonan, Tan, Yajun
• Format: Article
• Language: English
• Subjects: Animals; anticholinesterase; ChE; Chlorpyrifos - toxicity; Cholinesterase Inhibitors - toxicity; Cholinesterases - biosynthesis; Cholinesterases - metabolism; Daphnia - anatomy & histology; Daphnia - drug effects; Daphnia - enzymology; Daphnia magna; Environmental Exposure - analysis; Enzyme Induction - drug effects; enzyme promotion; exposure; Freshwater; Organothiophosphates - toxicity; population prosperity; recovery culture; Reproduction - drug effects; Time Factors; Triazoles - toxicity; 三唑磷; 乙酰胆碱; 体内活性; 大型溞; 慢性; 毒死蜱; 毒物兴奋效应; 胆碱酯酶
• ISSN: 1001-0742; 1878-7320
• DOI: 10.1016/S1001-0742(10)60516-5

In vivo activity of cholinesterase （ChE） in Daphnia magna was measured at different time points during 21-day exposure to triazophos and chlorpyrifos ranging from 0.05 to 2.50 μg/L and 0.01 to 2.00 μg/L, respectively. For exposure to triazophos, ChE was induced up to 176.5% at 1.5 μg/L and day 10 when measured by acetylthiocholine （ATCh）, whereas it was induced up to 174.2% at 0.5 μg/L and day 10 when measured by butyrylthiocholine （BTCb）. For exposure to chlorpyrifos, ChE was induced up to 134.0% and 160.5% when measured by ATCh and BTCh, respectively, with both maximal inductions detected at 0.1 Ixg/L and day 8. Obvious induction in terms of ChE activity was also detected in daphnia removed from exposures 24 hr after their birth and kept in a recovery culture for 21 days. Results indicated that the enzyme displayed symptoms of hormesis, a characteristic featured by conversion from low-dose stimulation to high-dose inhibition. In spite of that, no promotion in terms of reproduction rate and body size was detected at any tested concentrations regardless of whether the daphnia were collected at end of the 21-day exposure or at end of a 21-day recovery culture. This suggested that induction of ChE caused by anticholinesterases had nothing to do with the prosperity of the daphnia population.