Adenosine deaminase activity in human diploid skin fibroblasts varies with the age of the donor

Activities of adenosine deaminase, adenosine kinase and purine nucleoside phosphorylase were determined in extracts prepared from human skin fibroblast strains derived from 7 normal newborn males and 4 normal adult males. All strains were harvested between passages 9 and 12. Adenosine deaminase activity in adult strains, 40.80 ± 1.76 (mean ± S.E.) nanomoles/min per mg protein, was almost twice the activity in neonatal strains, 22.40 ± 3.02. This difference was significant at the 99.5% confidence level. Moreover, there was no overlap between the adult and neonatal activities. In contrast, adenosine kinase and purine nucleoside phosphorylase activities did not differ with the age of the donor.