The a-amylase Activity in the Urine o/Healthy School Children Summary. The introduction of new laboratory methods requires a review of the "normal values". The micro-and ultra micro method for the determination of a-amylase activity by Street and Close, already used successfully by many laboratories, allows the determination of enzyme activity in many biological fluids but calls for a re-assessment of the so-called "normal values". In this study the results of determinations done on 210 school children are presented. The tests were perfomed with urine samples from a three hour period, collected under standard conditions. An exact statement of the quantity of a-amylase excreted with the urine per unit of time was thus made possible.The 210 children belonged to two age-groups: either 7--8 or 11--12 years old. The three parameters determined from the three hour sample were: Quantity, specific weight, and a-amylase activity. We were able to confirm our own earlier findings that the enzyme activity increases with age, in both, activity and quantity. Significant sex-dependent differences were not observed. The normal range of values of a-amylase concentration in urine was found to be between 40 and 250 SCU (Street-Close Units) per 100 ml urine and the total excretion within three hours ranged from 25--200 SCU. A correlation between a-amylase concentration and specific weight of the urine was not observed. This form of test implies an improvement of the diagnostic possibilities.~chliisselw6rter: a-Amylase im Urin --Normalwerte --gesunde Schulkinder.Die Einffihrung neuer Methoden in die klilfischen Laboratorien macht die st~ndige Uberarbeitung und Ergi~nzung der j eweiligen ,,Normalwerte" erforderlieh. Die bereits in vielen Kliniken angewandte Mikro-und Ultramikromethode yon Street u. Close [15,17] zurBestimmung der a-AmylaseAktivi~t in verschiedenen biologisehen Fliissigkeiten macht die Aufstellung eines kompletten Ka~aloges yon Normalwerten dieser Hydrolase in den einzelnen K6rperfliissigkeiten notwendig.Die a-Amylase, 3,2,1,1-a-1,4-Gluean-4-glueanohydrolase, ist ein Me. talloenzym, als dessen Stabilisator Calcium fungiert. Das Molekfil bes~eh~ aus 18 Aminos~uren, vorwiegend Glyein, Lysin, Arginin und Aspar~gin. Ffir die Ak~ivit~t des Enzyms sind seine prim~ren Aminogruppen yon besonderer Bedeutung, die Hydroxylgruppen k61men da-
