Circadian variations and reference intervals for some enzymes in urine of healthy children.

Circadian variations of alanine aminopeptidase (EC 3.4.11.2), gamma-glutamyltransferase (EC 2.3.2.2), and N-acetyl-beta-glucosaminidase (EC 3.2.1.30) in urine were studied in 10 healthy children, ages six to 15 years. Urine specimens were collected during 24 h, grouped into four time intervals. Enzymes were measured spectrophotometrically, with automation. These enzymes all showed diurnal variation, with morning (8 a.m.-12 noon) excretion being highest. We also analyzed timed urinary specimens (8 a.m.-12 noon) from 136 healthy children, ages two to 11 years. Reference intervals are presented for these enzymes. High excretion of the three enzymes was observed in children two and three years old.