Cyclosporine nephrotoxicity and rejection crisis: Diagnosis by urinary enzyme excretion

The urinary enzymes alanine aminopeptidase (AAP; EC 3.4.11.2) and N-acetyl-B-D-glucosaminidase (NAG; EC 3.2.1.30) were measured daily in 35 renal transplant recipients during the early postoperative period. Each peak value of fractional excretion was corrected for its baseline value (CFE). CFE values above normal for both NAG and AAP were more frequently found in episodes of acute rejection than in cyclosporine acute nephrotoxicity episodes (76 vs. 0%; p < 0.001). Consequently, a rise in CFE levels for both NAC and AAP is strongly suggestive of acute rejection crisis.