Urinary gamma-glutamyl transpeptidase, an indicator of renal ischaemic injury and homograft rejection.

Gammaglutamyl transpeptidase is an enzyme primarily located in the brush border of the proximal convoluted tubules of the kidney. Its unique localisation in the renal cells most easily damaged by ischaemia and its ease of assay provides the rationale for its use in the measurement of renal ischaemic injury. Using a standard experimental animal model, canine urinary gamma-GT activity was shown to be increased up to 70-fold following 90 min of unilateral renal ischaemia and was significantly raised following only 5 min ischaemia. The urinary gamma-GT was used as a measure of ischaemic injury associated with renal transplantation in man and 20 consecutive patients undergoing kidney transplant were studied by daily 24-hour urinary gamma-GT estimations and excellent correlation was obtained between raised enzyme activity and the clinical diagnosis of transplant rejection.