The influence of age on the activity of acetylsalicylic acid-esterase and protein-salicylate binding

Summary

The activity of acetylsalicylic acid-esterase (ASA-esterase) in blood and the degree of protein-salicylate binding were estimated in different age groups. The activity of ASA-esterase was assayed by the amount of salicylate released after incubation with ASA under standard conditions. Lower activity of the enzyme was found in neonates (48–49% of ASA hydrolysed after 60 min) than in older children (60–64% hydrolysed) and male adults (78–83% hydrolysed). The erythrocytes of adult females were less active than those from males. Protein-binding of salicylic acid (SA) was also lower in neonates than in adults (30.7% at SA 68.4 µg/ml, and 52% at 10.28 µg/ml SA, respectively). Even if the protein concentration in adult plasma were reduced to the level of the neonates by dilution, and if bilirubin were added to the mixture, the protein-binding was still greater in plasma from adults than neonates. These observations suggest that in the neonatal period the protein-affinity of certain substances may differ from that in adults.