Spontaneous reactivation of fenitro-oxon-inhibited plasma cholinesterase in various mammals

It was investigated as to whether a spontaneous reactivation was also observed in fenitro-oxon-inhibited plasma cholinesterase (ChE) of human and several animals, such as mice, guinea pigs and rabbits, as previously reported in rat plasma ChE. It was found from the results that a marked spontaneous reactivation took place during storage at 37 degrees C or 24 degrees C in all of human and the animals, while these reactivations of animals were to some extent slower and slighter than that of rat. Moreover, there was little significant difference between the spontaneous reactivations observed in using acetylthiocholine and butyrylthiocholine as a substrate, although the use of the latter substrate resulted in somewhat faster and greater spontaneous reactivation only in rat. These results suggest that the spontaneous reactivation takes place in plasma pseudo ChE of various animals after inhibition with fenitro-oxon.