In-vitro and in-vivo protection of acetylcholinesterase by eseroline against inactivation by diisopropyl fluorophosphate and carbamates

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Abstract
The protective action of eseroline—(3aS, 8aR)‐l,2,3,3a,8,8a‐hexahydro‐l,3a,8‐rimethyl‐pyrrolo[2,3‐b]indol‐5‐ol—salicylate against (DFP) diisopropyl fluorophosphate and carbamate poisoning of cholinesterases (ChEs) has been examined in‐vitro with human erythrocytes and purified preparations of electric eel acetylcholinesterase (AChE) and of horse serum butyrylcholinesterase (BuChE), and in‐vivo using mice. Eseroline afforded 50% protection (ED 50) of erythrocyte AChE against inactivation by 1 μM DFP, physostigmine or neostigmine, at concentrations of 4.3, 22 and 23.5 μM, respectively, while for eel AChE protection against 10 and 30 μM DFP, 0.3 and 1 μM physostigmine and 1 μ m neostigmine the eseroline ED 50 values were 0.3, 0.4. 0.7, 1.9 and 5.6 μM, respectively. On the other hand, up to 0.3 mM eseroline did not appreciably affect the inhibitory action of the same drugs on horse serum BuChE. Eseroline concentrations in the range 0.1‐1 mM were able to reactivate 20‐42% of erythrocyte AChE previously inhibited by 100 μM physostigmine, but failed to reactivate the DFP (10 μM)‐pretreated enzyme to any extent. Finally, eseroline salicylate injected into mice (10 mg kg−1 s.c.) protected an average of 82 and 26% of the animals against lethal doses of DFP (7mg kg−1 s.c.) and physostigmine sulphate (1 mg kg−1 i.p.) respectively, which were administered 15 min later. These results indicate that the protective activity of eseroline correlates well with its own anti‐ChE profile, and that the effectiveness of the protection depends largely on the rate of AChE inhibition by the agents used to inactivate the enzyme.