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

Abstract

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 K_m values of both nucleosides were comparable in 3- and 40-day-old rats.

Ontogenesis of Adenosine Deaminase Activity in Rat Brain

“…Kinetic analysis of ADA activity in whole brain at various developmental stages demonstrated that the observed differences in activity were due to changes in V,, of the enzyme rather than an altered K , for its substrate. The present K , values were similar to those previously reported for brain (Pull and McIlwain, 1974;Arch and Newsholme, 1978;Phillips and Newsholme, 1979;Geiger and Nagy, 1986) and peripheral tissues (Peters et al, 1982). Although the K , values observed here on the third postnatal day were significantly lower than at 18 days gestation, the physiological significance of this finding is at present unclear.…”

“…Although the K , values observed here on the third postnatal day were significantly lower than at 18 days gestation, the physiological significance of this finding is at present unclear. For thymocytes, Peters et al (1982) reported the K, value of ADA in 3-day-old rats to be similar to that in animals 40 days of age.…”