Diurnal variations of urinary enzyme excretion

Variations in the urinary excretion of arylsulphatase A, beta-galactosidase, alpha-glucosidase and beta-glucuronidase throughout a 24-h period were studied in 8 healthy subjects. Urine was collected at 3-h intervals and enzyme activities were assayed after gelfiltration of the urine specimens. Significant intra-individual changes of the excretion of all 4 enzymes during the 24-h period were found. Enzyme output was high between 3 a.m. and 9 a.m. and low during the afternoon and evening hours. The most striking pattern was seen for arylsulphatase A. Diurnal variations of urinary enzyme excretion seemed not to be flow dependent. Both modes of expression of enzyme output (mU/min or U/g creatinine) gave corresponding results. It is concluded that for the measurement of the excretion of these enzymes urine should be collected during a fixed time interval, e.g. from 6 a.m. to 9 a.m.