The Fate of P32 Labelled Diisopropylfluorophosphonate in the Human Body and Its Use as a Labelling Agent in the Study Of The Turnover of Blood Plasma and Red Cells

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Abstract
Five human subjects were injd. intramusc. with varying nontoxic doses of diisopropylfluorophosphonate labelled with P32 (DFP32). Under normal conditions radioactivity originating from DFP could be domonstrated in peripheral blood within a few min.; max. radioactivity was reached in 90 min. A small portion of the injd. P32 was irreversibly bound to red cells and plasma. This fraction disappeared from the blood at a rate corresponding to the normal replacement of these elements. This relationship could be exploited to calculate the rate of replace-ment of a plasma protein and the mean life span of red cells. Values of 12-14 days were found for the half life of this plasma component in 4 persons. A mean red cell life span of 116 and 129 days, respectively, was found in 2 subjects. Injd. DFP is excreted in the urine as diisopropylphosphate (60-70% in the 1st 10 days); less than 5% of the P32 injd. as DFP is recovered in the feces during that period. It is suggested that labelling by means of DFP32 may also be used for the evaluation of red cell and plasma vol.