DISTRIBUTION OF RADIOPHOSPHORUS IN RABBIT TISSUES AFTER INJECTION OF PHOSPHORUS-LABELED DIISOPROPYL FLUOROPHOSPHATE

¹ Biochemistry Section, Medical Division, Army Chemical Center, Maryland

When phosphorus-labeled DFP (3-4 millicuries P³² per millimol) is injected intravenously into rabbits, radiophosphorus is retained in relatively large amounts by kidney, liver and lung, while other organs take up only small or insignificant amounts. The specific retention of P³² depends on the dose administered, and on the length of survival. No correlation seems to exist between the cholinestera. se activity of rabbit organs, and their ability to retain DFP-derived phosphorus. No significant retention of P³² in any tissue was found when labeled diisopropylphosphate was administered.

Of the total amount of DFP-derived P³² retained in liver, lung and kidney, a fraction which reaches 100 per cent after four hours of survival is bound to tissue proteins.

In plasma of rabbits injected with labeled DFP, most of the P³² originally present is eliminated before regeneration of cholinesterase activity has started. In erythrocytes the elimination of P³² parallels the reappearance of cholinesterase, indicating the destruction of cells whose cholinesterase was inactivated by DFP and their replacement with new cells containing active esterase.

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