Research into selective biomarkers of erythrocyte exposure to organophosphorus compounds

Flowcytometric procedures provide distinct advantages over the colorimetric methods currently in use to monitor erythrocytes for exposure of patients to organophosphorus (OP) pesticides and chemical warfare agents; therefore, they warrant exploration. Two types of fluorescent probes—one to detect the total acetylcholinesterase on erythrocytes (RBC–AChE) and the other to distinguish between the active and OP-inhibited RBC–AChE—have been explored. Our studies demonstrate that a fluorescently conjugated fasciculin can be used to monitor total, active, and OP-inhibited RBC–AChE. However, a fluorescently tagged potent inhibitor of AChE, TZ2PIQ-A6 with a Kd of 33 fM, did not distinguish between the active and OP-inhibited RBC–AChE, nor did three different biotinylated OP compounds. The biotin–fluorescent avidin approach is not a viable procedure for monitoring RBC–AChE. Western blot studies indicate that there are at least 20 serine hydrolases on the surface of red blood cells (RBCs). Plans currently under way for the development of more specific probes to distinguish between active and OP-inhibited RBC–AChE are discussed.