Which enzyme is measured in red blood cells as a marker of organophosphate exposure?

• A. Acetylcholinesterase
• B. Butyrylcholinesterase
• C. Alkaline phosphatase
• D. Lactate dehydrogenase

Answer: (A)

Organophosphate exposure works by blocking cholinesterase enzymes, preventing the breakdown of acetylcholine and leading to toxic effects. Measuring acetylcholinesterase activity in red blood cells provides a direct readout of how much this enzyme has been inhibited, and because the erythrocyte enzyme is the same type as the neural one, its inhibition mirrors what would happen at nerve endings. This makes red blood cell acetylcholinesterase a practical and informative marker for exposure and helps gauge the severity of inhibition. The other enzymes listed aren’t specific markers of organophosphate exposure—alkaline phosphatase and lactate dehydrogenase indicate general tissue or cellular turnover, while butyrylcholinesterase in plasma can be variably affected and is not measured in red blood cells for this purpose.