PURINE TRANSPORT IN POLYMORPHONUCLEAR LEUKOCYTES

The uptake of adenine and xanthine has been studied in rabbit polymorphonuclear neutrophilic leukocytes. Since purines were found to enter neutrophils rapidly a technique was developed for taking initial rate samples as quickly as 10 sec, using cell monolayers on glass coverslips. Adenine was found to enter neutrophils by two saturable transport systems, one with a high affinity and a low maximal velocity, the other with a low affinity and a high maximal velocity. Xanthine enters predominantly by a transport carrier that is distinct from either of the adenine systems. In addition some xanthine entry occurs which cannot be overcome by a competitive inhibitor. Within the cell adenine was metabolized to adenosine nucleotides and xanthine to uric acid. Both products accumulated within the cell. From the absence of free adenine within the cell it was concluded that a low concentrations the limiting step to adenine incorporation into nucleotides was its entrance into the cell. © 1969.