Isoenzymes of urinary N-acetyl-beta-D-glucosaminidase (NAG) in patients with renal transplants.

Renal transplant recipients were divided into five categories according to their clinical course from transplantation to their discharge from hospital. Total N-acetyl-beta-D-glucosaminidase (NAG) activity in urine was determined using a chromogenic substrate 2-methoxy-4-(2'-nitrovinyl)-phenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside. The isoenzyme composition of the urine of each patient was determined by semi-automated DEAE-cellulose chromatography. Although raised NAG activity was found in stable transplant patients compared to controls, the level of activity was constant and no change in the isoenzyme profile was found. In reversible rejection there was a marked increase in the intermediate forms, particularly I2 and a concomitant fall in the relative amount of the A-form present but the profile became normal when the patient stabilised. Much more complex patterns were observed in patients who did not respond to treatment. Both the B and I forms were elevated with a fall in the A-form and in one case excretion of the serum As form was observed. The intermediate forms were always increased in rejection.