Author copy • Author copy • Author copy • Author copy • Author copy • Author copy • Author copy • Author copy • Author copy Introduction Organophosphates are chemicals that inhibit cholinesterase and are employed widely as pesticides in residential settings and in agricultural practice to increase crop yields. Because the use of organophosphate pesticides has been and remains pervasive in both developed and developing nations, concerns are increasing regarding the relative safety of these chemicals for the environment, humans, and animals [1]. One such organophosphate that has spurred renewed interest is chlorpyrifos, the most wide- ly used insecticide in the world. Chlorpyrifos [O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothionate is utilized extensively in agriculture and for residential pest control. Today it is registered in about 100 countries worldwide and more than 50 crops are pro- tected from insect infestation with its products. It is effec- tive in controlling cutworms, corn rootworms, cockroaches, grubs, flea beetles, flies, termites, fire ants, and lice in grain, cotton, fruit, nut, and vegetable crops, as well as on lawns and ornamental plants. It is also registered for direct use on sheep and turkeys, for horse site treatment, dog kennels, domestic dwellings, farm buildings, storage bins, and com- mercial establishments [2]. LD 50 for chlorpyrifos is 60 mg/kg in mice, 1000 mg/kg in rabbits, 32 mg/kg in chickens, 500 to 504 mg/kg in Pol. J. Environ. Stud. Vol. 21, No. 4 (2012), 1001-1006 *e-mail: pistl@uvlf.sk Original Research Use of Cultured Cells of Mammal and Insect Origin to Assess Cytotoxic Effects of the Pesticide Chlorpyrifos Jana Polláková 1 , Juraj Pistl 1 *, Natália Kovalkovičová 2 , Tomáš Csank 1 , Alica Kočišová 3 , Jaroslav Legáth 2 1 Department of Microbiology and Immunology, 2 Department of Pharmacology and Toxicology, 3 Department of Epizootology and Parasitology, University of Veterinary Medicine and Pharmacy, Komenského 73, 041 81 Košice, Slovak Republic Received: 20 July 2011 Accepted: 12 January 2012 Abstract In the present study four different cell cultures, derived from rabbit kidney (RK13), rat, and murine liver (WBF344 and Hepa 1c1c7) and insect origin (Sf21) were used to examine the effects of chlorpyrifos. Sf21 cells were the most sensitive to chlorpyrifos, with significant suppression of their proliferative activity rang- ing from 10 -1 -10 -5 M. However, significant suppression of proliferative activity also was recorded in mam- malian cell cultures Hepa 1c1c7 (10 -1 -10 -3 M), WBF344 (10 -1 -10 -2 M), and RK13 (10 -1 M). A cytopathic effect and LDH leakage into the medium was observed in RK 13 (10 -1 -10 -3 M) > WBF344 and Hepa 1c1c7 cells (10 -1 -10 -2 M) > Sf21 (10 -1 M) compared to solvent control. Our results indicate that chlorpyrifos exposure caused a species-dependent decrease in cell proliferation and cell membrane damage. Keywords: insecticide, chlorpyrifos, cell cultures, cell proliferation, LDH