Leukocyte labeling with inorganic radiophosphorus

¹ Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina

Plasma clearance of inorganic P³² given in a single intravenous injection has been evaluated. Significant levels of activity persist for at least 7 days following injection of only 2 µc/kg. Inorganic P³² uptake into various fractions of circulating leukocytes and into fractions of marrow cells has been studied. In marrow cells, equilibration of extracellular phosphate and intracellular acid-soluble organic and inorganic phosphates appears to be reached by 24 hr and probably occurs sooner. In leukocytes thought to be postmitotic at the time label is injected this equilibrium is not reached until 48 hr. In rabbits the postmitotic maturation pool is sufficient to replace circulating leukocytes for at least 48 hr; this defines the time required for cell passage through this pool under normal conditions. Significant deoxyribonucleic acid tagging from a single intravenous injection of P³² appears to proceed for several days.