We gave mice a 540 mg/kg dose of LD50
acephate, followed by an assessment of
acephate,
methamidophos (MP), and
choline esterase (ChE) activity for up to 4 hours (hr) in order to investigate the time course of
acephate intoxication. At 1 hr, the blood
acephate and MP levels were 428 ± 90 µg/ml (mean ± SEM) and 4.2 ± 0.4 µg/ ml, respectively. The liver
acephate levels were similar to those in the blood, but the liver MP levels were approximately 3.5 times that of the blood at 1 hr. The brain MP level tended to be higher than the blood MP at 1 hr. These levels decreased gradually over 4 hr, but the brain
acephate and MP levels surpassed the blood levels significantly at 4 hr, and after 2 hr, respectively. Serum, liver, cerebrum, cerebellum, and brainstem
cholinesterase activity (ChE) were inhibited at 1 hr, and remained inhibited in all but the cerebellum until the end of the experiment. The obtained data were applied to previously reported autopsy cases of
acephate intake. Experimental data suggest that brain MP is involved in acute
acephate-induced
poisoning, even after a reduction in blood
acephate. In autopsy cases with suspected
acephate poisoning, the MP level in the brain should be considered in addition to the ChE activity to diagnose the cause of death.