Chlorpyrifos (CPF) (C9H11Cl3NO3PS) is one of the most well-known organophosphates. Due to its low cost and high efficiency as a pesticide, this compound is widely used in the agriculture of Ukraine, in pure form, as well as the active ingredient of a number of integrated agro-chemical means, thus causing the risk of intoxicating humans.

Particularly important is to study the primary toxic reactions of organisms at chronic and sub-chronic exposure to low doses of HPF. The aim of our work was to investigate the effect of long-term (over 30 days) low dose (5 mg/kg, 10 mg/kg, 15 mg/kg) HPF intoxication on the main parameters of hematological profile of Wistar rats. We formed four groups (control (C) and three experimental (D1, D2 and D3)) with 10 rats in each. Animals of the experimental groups were exposed to HPF (Sigma-Aldrich ( USA ), dissolved in vegetable oil, every day for a month via oral probe, doses of CPF were 5 mg/ kg (group D1 ), 10 mg/kg (group D2) and 15 mg/kg (group D3). Intact animals of the control group were exposed to an equivalent amount of clean vegetable oil.

After cease of CPF exposure, at 30th day, blood for analysis was taken from the tail vein of rats. Blood samples were analyzed on an automatic hematologic analyzer (Orphèe Mythic 18, Switzerland). Following parameters were studied: the number of red blood cells, white blood cells, lymphocytes, monocytes, granulocytes, platelets, hemoglobin concentration, hematocrit, trombocrit, mean platelet volume and platelet volume heterogeneity index.

Significant changes were observed in red blood cells of rats exposed to different doses of CPF. In particular, in the blood of rats of the third experimental group, exposed to 15 mg/kg CPF, was detected a 27% (p<0,05) decrease in the number of red blood cells, 25% (p<0,05) decrease in hemoglobin concentration, and 29% (p<0,05) in hematocrit index, compared to control. CPF in smaller doses (5 mg/kg, 10 mg/kg) is not likely to cause changes of these parameters. Mild intergroup differences were observed in parameters of peripheral blood, such as the average erythrocyte volume, mean corpuscular hemoglobin amount and mean corpuscular hemoglobin concentration, after exposure to different doses of toxicant. Changes in the white blood parameters also were observed. In particular, in the blood of the third experimental group of rats significant 39% (p<0,05) increase in the number of white blood cells, 50% (p<0,05) in lymphocytes, compared to the control group was detected. We observed significant 70% (p <0,05) increase in the total number of granulocytes in the third group, compared with control. We detected changes in platelets and certain platelet indexes - at CPF dose 5 mg/kg was observed a significant 47% (p<0,05) decrease in the number of platelets in the first group, compared to control, and 47% (p<0,05 ) decrease in trombocrit index compared to control values. In contrast, in the blood of animals of the third experimental group, exposed to 15 mg/kg HPF, 33% (p<0,05) increase in the total number of platelets, compared to control was observed. 30% (p<0,05) increase in trombocrit index was observed in the third experimental group, compared to control. No significant changes were observed in the mean platelet volume in any group of experimental animals. Platelet heterogeneity index increased by 21% in the second group, compared with control, but this increase appeared statistically unreliable.

Keywords: chlorpyrifos, rats, blood

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