EFFECT OF TIME AND STORAGE-TEMPERATURE ON CHOLINESTERASE ACTIVITY IN BLOOD FROM NORMAL AND ORGANOPHOSPHORUS INSECTICIDE-TREATED HORSES

Delays between time of sampling and time of testing are common; theref ore, the length of time that blood can be stored at various temperatur es was evaluated for effects on cholinesterase activity. Six horses we re treated with 16 g of trichlorfon per os, 6 horses were treated with 15 g of dichlorvos per os, and 10 horses were untreated controls. The cholinesterase activity in whole blood from each horse was measured u sing an adaptation of the Ellman colorimetric method. The blood from e ach horse was then divided into 3 groups and stored at 5 C (refrigerat ed), 20 C (room temperature), or 38 C (incubated). Subsequent cholines terase activities were measured daily and then at weekly intervals. Th e cholinesterase activities did not significantly increase or decrease (P > 0.05) in the blood from the untreated horses until after 1 week for any of the 3 temperature groups. The cholinesterase activities did not significantly increase or decrease (P > 0.05) in the stored blood from the trichlorfon-treated horses for 4 weeks in all 3 temperature groups. The cholinesterase activities significantly increased (P < 0.0 5) in the stored blood from the dichlorvos-treated horses after 1 week when the blood was refrigerated and by 24 hours when the blood was st ored at room temperature or incubated. Therefore, blood from normal or organophosphate-treated horses can be used for cholinesterase evaluat ion for up to 1 week when stored at 5 C.