Evolution of fetal and adult thymidine kinase isoenzymes in rat ventral prostates during development

Thymidine kinase activity exhibited important changes during prostate growth. It increased considerably during the prepubertal period and reached a maximum level on day 55 of age. Then, it decreased gradually to the low values observed on and after day 90. Changes in enzyme activity were due mainly to variations in the activity of the fetal isoenzyme, which was maximum from day 45 to day 55 and decreased to undetectable levels on and after day 90 of life. The low thymidine kinase activity observed at the same time was due to the adult isoenzyme alone. Administration of 5α-dihydrotestosterone to animals resulted in the considerable increase in fetal thymidine kinase activity. The stimulation of the fetal isoenzyme by androgens was maximum during the prepubertal period and decreased thereafter.