Characterization of placental cholinesterases and activityinduction associated to environmental organophosphateexposure

Abstract

Although non-innervated, the placenta contains both cholinesterases (ChEs), butyryl-cholinesterase (BChE) and acetylcholinesterase (AChE). These enzymes are well-known fortheir multiple molecular forms. In a first approach, we used recognized specific inhibitors,substrate preferences and non-denaturating gel electrophoresis in order to characterize theChE profile of term placenta from uncomplicated pregnancy. Results strongly suggest thatthe predominant cholinesterasic form present was tetrameric BChE.It is well established that both ChEs are targets of cholinesterase-inhibiting organophos-phates (OP), one of the most important classes of chemicals actively applied to theenvironment. However, we have previously reported increased ChEs activity in placenta ofrural residents exposed to OP. In the present work, we have studied: 1) whether this find-ing was reproducible and, 2) whether AChE or BChE up regulation is behind the increase ofplacental ChE activity. The population studied included forty healthy women who live inan agricultural area. Samples were collected during both the OP pulverization period (PP)and the recess period (RP). The placental ChEs activity increased in PP, evidencing repro-ducibility of previous results. The analysis of non-denaturating gels revealed that increasedactivity of total ChE activity in placenta from women exposed to OP may be attributable totetrameric BChE up-regulation.