In vitro studies upon the release of gamma-glutamyltransferase from human liver

Samples of human liver have been incubated in different fluids for up to 48 h and the released gamma-glutamyltransferase studied by gel chromatography on Sephacryl S-300 and polyacrylamide gradient gel electrophoresis. When human liver is incubated in serum, most of the released enzyme is of high Mr (greater than 1,000,000). Incubation in hepatic bile, or in a solution of glycochenodeoxycholate, results in the release of enzyme that is hydrophobic in nature and which reaggregates to a varying extent after the removal of bile salts. In contrast, incubation in saline, or in a solution of human albumin results in the release of a hydrophilic low Mr (about 120,000) form of the enzyme. These observations are discussed in relation to possible mechanisms for the release of these multiple forms.