Age-Dependency of Adenosine Deaminase and Purine Nucleoside Phosphorylase Activities in Rat Spleen and Thymus

Activities of adenosine deaminase and purine nucleoside phosphorylase were determined in thymocytes and splenocytes of rats of 0-423 days old. Activity of adenosine deaminase per cell is highest in newborn rats and decreases with postnatal development, while in splenocytes adenosine deaminase activity increases. No significant age-dependency is found with purine nucleoside phosphorylase in thymocytes and splenocytes. During whole life adenosine deaminase activity is higher in thymocytes and purine nucleoside phosphorylase activity is higher in splenocytes. With thymocytes, adenosine deaminase activity was higher with deoxyadenosine than with adenosine. The Km values of both nucleosides were comparable in 3- and 40-day-old rats.