Purine nucleoside phosphorylase heterogeneity in the mouse as analyzed by isoelectric focusing and specific activity.

1. Isoelectric focusing in polyacrylamide gels identified three erythrocytic electrophoretic patterns of purine nucleoside phosphorylase in a survey of 16 mouse strains. 2. Three strain-specific electrophoretic types were also evident in liver, kidney and spleen leukocytes. 3. There are 3-fold differences in purine nucleoside phosphorylase activities between strains for several tissues; C57BL/6J and Mus spretus having the greatest and the least activity, respectively. 4. Within strains there were up to 8-fold tissue-specific differences in activity with the order from greatest to least being: liver, kidney, spleen leukocyte, erythrocyte, heart.