Selective inhibition of true and pseudo-cholinesterases in frog rectus

Abstract

The hydrolysis of acetylcholine chloride (0.01M) by frog's rectus extracts, is inhibited by low concentrations of 3318 CT (CI-50 3.2×10−7) and high concentrations of D.F.P. (CI-50 1.3×10−5). Inversely, the hydrolysis of butyrylcholine perchlorate is inhibited by low concentrations of D.F.P. (CI-50 3×10−9) and high concentrations of 3318 CT (CI-50 3×10−4). Both are inhibited by similar concentrations of neostigmine (CI-50 1.1×10−7 and 1.5×10−7). Frog's rectus thus contains true and pseudo-cholinesterases. The inhibitions produced by D.F.P. added to the muscle itself (and not the extract) correlates well with the potentiation of the corresponding ester. Sensitization to AcCh and to BuCh appears to be specifically related to the inhibition of Ac ChE for the former ester, of XChE for the second one.