GAMMA-GLUTAMYL-TRANSFERASE IS A RELIABLE MARKER FOR TUBULAR EFFECTS OF CONTRAST-MEDIA

The aim of this study was to evaluate the usefulness of the measuremen t of urinary excretion of the brush-border enzyme gamma glutamyltransf erase (GGT), in comparison with that of alanine aminopeptidase (AAP), as a marker for tubular toxicity due to contrast media (CM). Urinary a ctivities of AAP and GGT were measured prior to the administration of CM and 1, 3 and 5 days after in forty-nine adult renal patients underg oing a radiological examination with intravascular administration of C M. The behavior of CGT was similar to that of AAP. In fact, urinary ac tivities of both AAP and GGT increased greatly after CM. This effect w as maximal on the 1st day and statistically significant for both enzym es. Furthermore, on the 1st day a relevant increase of enzyme activity (at least +50% over the basal value) was observed in the same number of patients (67%) for AAP and GGT. The concordance between GGT and AAP variations was high and statistically significant Finally, different variables (osmolarity, dose of CM, and baseline renal function of the patients) had a similar effect on urinary excretion of AAP and GGT.The repeatability of duplicated determinations of GGT resulted better tha n that of AAP. In conclusion, the good concordance of the results of G GT with those of AAP justifies the use of GGT as a marker for tubular effects due to CM. Furthermore, the measurement of GGT has a better re peatability than that of AAP.