Chemical reactivations of inactivated acetylcholinesterase after 2-PAM therapy in fenitrothion-poisoned rat and rabbit.

We investigated the reactivation of inactivated acetylcholinesterase (AChE) after 2-PAM therapy in acute fenitrothion poisonings of two species of rat and rabbit. By single treatment with 2-PAM carried out immediately after fenitrothion administration, the significant reactivations of inactivated AChE in red blood cell (RBC) and brain as well as inactivated cholinesterase (ChE) in plasma were observed at 2 h after administration of 20 mg/kg fenitrothion in rat, while these reactivations became less in rats severely poisoned with 500 mg/kg fenitrothion. Although these significant reactivations disappeared 6 h after the single treatment with 2-PAM, the repeated treatments with 2-PAM induced the prolongation of the reactivations of inactivated AChEs and ChE. These results suggest that 2-PAM would be more effective to light poisoning with fenitrothion, and that the repetition of 2-PAM treatment would be very important to obtain the sufficient antidotal actions. In rabbits as well as rats, the considerable reactivations of inactivated AChEs in RBC and brain and inactivated ChE in plasma were observed by the single treatment with 2-PAM in fenitrothion poisoning. These reactivations in brain AChE indicate that 2-PAM can penetrate the blood brain barrier of both rat and rabbit, despite its quaternary character.