Preparation of urine for enzyme determinations by gel filtration.

The activities of several enzymes in urine are masked by the presence of interfering substances in native urine. From several methods proposed for the removal of low molecular mass interferences dilution, dialysis, gel filtration, and ultrafiltration have been successfully applied. Gel filtration seems to be of these most suitable. I is effective, accurate, precise and economical. Scale-down procedures provide for acceptable speed. By this method the complete separation of lactate dehydrogenase, gamma-glutamyltransferase, alkaline phosphatase, arylsulphatase A, alpha-glucosidase, beta-galactosidase, trehalase, N-acetyl-beta-glucosaminidase, beta-glucuronidase and leucine arylamidase from low molecular mass substances, e.g. a heat-stable, competitive inhibitor of N-acetyl-beta-glucosaminidase was possible. The preparation and determination of urinary enzymes should be thoroughly standardized and controlled. Acceptable precision (coefficient of variation less than 10% between-day) can be achieved with manual spectrophotometric methods.