Synthesis of human gamma-glutamyl transpeptidase (GGT) during the fetal development of liver

We have determined expression of human GGT gene encoding γ-glutamyl transpeptidase (GGT) during fetal development of liver using the Northern-blot analysis with a cloned human GGT cDNA and immunohistochemistry with a monoclonal antibody. GGT mRNA could be detected as early as the 12th week of gestation. It then increased gradually to a peak of approx. threefold the amount at week 12, at week 40, just before birth. The size of the mRNA in the fetal liver was 2.7 kb and mRNA of the same size was detected both in the human fetal kidney and human hepatocellular carcinoma as well as normal adult liver. Immunohistochemical analyses show that GGT increased as the fetal liver developed in parallel with the increase in mRNA. Histochemically, GGT was shown to be located in the wall of bile canaliculi when synthesis was low in early development, but to be distributed, in addition, all over the cell membrane of the fetal hepatocytes when synthesis was high at the later stage of development.