Tzatzarakis M., Alegakis A., Toutoudakis M., Tsatsakis A.M., Dolapsakis G., Tsadik A., Psaroudakis K.

Toxicology Laboratory, Medical School, University of Crete, Stavrakia, Iraklion, PO Box 1393, 71409 Crete, Greece

The aim of this work was to study the incorporation of the pesticide methomyl (a carbamate insecticide) into the hair of rabbits.
Methods. White rabbits of the New Zealand variety were used for the experiment. Rabbits underwent veterinary examination in order to determine that they were in good health, before commencing the treatment. A total amount of 634 mg of methomyl was administered to the rabbits over a period of four months. Each dose was 20 mg per 1500 ml of drinking water and was consumed by the rabbits in four days. During the treatment period the activity of acetylcholinesterase in the serum was measured, using the cholinesterase determination kit by Boehringer Mannheim. At the end of the treatment period, hair from the back of the rabbits were cut off. Each sample consisted of 50 mg of hair that were powdered in a special homogenizer. The powder was dissolved in 2 ml of methanol and was incubated at 40° C for 18 hours. The solution was centrifuged and the supernatant was collected. Methanol was removed under a stream of N₂ and the residue was resuspended in 0.3 ml of distilled water. The methomyl concentration was measured using the Elisa Rapid Assay kit from Ohmicron.
Results. A decrease of acetylcholinesterase levels from reference values in rabbits serum during this period was observed. The analysis revealed that the first cm of hair from the root contained 3.15 ppb methomyl. The second cm from the root contained 0.75 ppb and the 3^rd cm of hair contained no methomyl.
Conclusion. Methomyl is incorporated in the rabbit hair. The incorporation of methomyl into the hair occurs through the bloodstream. The process seems to be dependent on the growth rate of the hair.