Increased serum gamma-glutamyltransferase activity in renal transplant recipients: liver damage or microsomal enzyme induction?

To investigate the reason for the increased activities of gamma-glutamyltransferase in the serum of renal transplant recipients, the activity of this enzyme was determined together with the alanine aminotransferase and alkaline phosphatase activity in serum (as an index of liver damage) and the urinary excretion of D-glucaric acid (as an index of microsomal enzyme induction) in 63 renal transplant recipients. Forty-one patients had increased activities of gamma-glutamyltransferase. Increased D-glucaric acid excretion was found only in ten patients having elevated alanine aminotransferase and/or alkaline phosphatase in seven cases and gamma-glutamyltransferase in eight cases. Therefore, the increased gamma-glutamyltransferase activities in renal transplant recipients can be primarily considered as a consequence of hepatobiliary dysfunction and not of enzyme induction.