A rapid and simple radiometric assay for thymidine phosphorylase of human peripheral blood cells

A radiometric method is described for measuring thymidine phosphorylase activity in human peripheral blood cells. The substrates [14C]thymidine or [14C]thymine are converted to the base or deoxynucleoside, respectively, and two alternative chromatographic methods to isolate the products of the reaction have been employed. With the described methods the specific activity for thymidine phosphorylase in human lymphocytes is 0.21 +/- 0.08; monocytes 0.21 +/- 0.16 and granulocytes 0.17 +/- 0.02 mu mol.h-1.mg-1 protein. For human T- or null lymphoblasts, thymidine phosphorylase activity was found to be approximately 10% of that of B lymphoblasts.