Giftung und Entgiftung von Parathion und Paraoxon

Summary

1. In experiments on rats and mice, paraoxon (E 600) was found to be less effective on intraperitoneal than on intramuscular injection: on intraperitoneal injection, the lethal dose (LD₅₀) as well as the dose causing 50% inhibition of the brain cholinesterase (ED₅₀) were about four times higher than on intramuscular injection (“detoxication by passage through the liver”).

2. Parathion (E605), on the other hand, was less effective on intramuscular than on intraperitoneal injection: on intramuscular injection, the LD₅₀ as well as the ED₅₀ were nearly twice as high as on intraperitoneal injection (“toxification by passage through the liver”).

3. The anticholinesterase agent 217-AO lost only little of its effectiveness by passing the liver following an intraperitoneal injection. In vivo, 217-AO was more effective than paraoxon, although 25 times higher concentrations are needed to inhibit the cholinesterase in vitro.

The results suggest that paraoxon is detoxicated by the liver so quickly that only a small fraction of the injected amount becomes effective, and that the “toxification” of parathion in the liver takes place more quickly than the detoxication of the paraoxon formed.

4. Dopamine was destroyed in the liver so quickly (monoamino-oxydase) that the intraperitoneal injection of a dose was ineffective which, on intramuscular injection, caused a strong rise in blood pressure.

5. Hexobarbital (Evipan) was destroyed in the liver so slowly (enzymes in the microsomes) that intraperitoneal and intramuscular injections were equally effective.

The different behaviour of the last two substances shows that it depends on the velocity of the inactivation in the liver whether or not there is a difference in effectiveness between intraperitoneal and intramuscular injections.