Determined were spectrophotometrically the normal values of the erythrocyte
cholinesterase of a total 272 sheep and 120 cattle under normal conditions. In sheep the average value of the
enzyme activity was within the range of 82 +/- 2.44, and in cattle it was 146 +/- 6.13 units. Experiments with 55 sheep, given
dipterex orally at rates of 150, 200 and 250 mg/kg liveweight each revealed that the activity of the
enzyme was below the lower normal value limit. The markedly expressed inhibition of the erythrocyte
cholinesterase was invariably accompanied with the clinical manifestation of organic
phosphorus intoxication. In some of the treated sheep there lacked clinical symptoms of
poisoning, although the activity of the erythrocyte
cholinesterase showed values ranging under the lower normal limit. It is believed that the inhibition of the
enzyme activity may well be referred to as the preclinical symptom of
poisoning with organic
phosphorus compounds, which, however, is not indicative of the severity of the disease in all cases. As there is no correlation between the clinical manifestation of the intoxication and the inhibition of the
enzyme activity animals suspicious of organic
phosphorus intoxication are to be studied in terms of the inhibition of their erythrocyte
cholinesterase activity.