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Expression of multiple proteins structurally related to gamma‐glutamyl transpeptidase in non‐neoplastic adult rat hepatocytes in vivo and in culture
Author(s) -
Mathis Georg A.,
Wyss Peter A.,
Schuetz Erin G.,
Hughey Rebecca P.,
Sirica Alphonse E.
Publication year - 1991
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041460207
Subject(s) - kidney , biology , in vivo , gamma glutamyltransferase , messenger rna , enzyme , microbiology and biotechnology , hepatocyte , biochemistry , glycoprotein , in vitro , endocrinology , gene
Abstract Freshly isolated hepatocytes from normal adult rat liver do not express measurable gamma‐glutamyl transpeptipdase (GGT) mRNA in contrast to the significant GGT mRNA levels expressed by normal adult rat kidney and hyperplastic bile ductular tissue from bile duct‐ligated rats. However, the induction of GG activity in rat hepatocytes by two‐thirds hepatectomy was accompanied by the appearance of a high level of GGT mRNA. We are now able to demonstrate that normal adult rat hepatocytes express 5 protein bands which cross‐react with 2 different anti‐rat kidney GGT antisera. The apparent molecular weights were 26.9, 58.0, 63.9, 73.5, and 83.4 kDa, respectively. Expression of the 26.9‐ and 58.0‐kDa proteins strikingly parallels the pattern of induction of GGT enzymatic activity. This suggests that these 2 proteins correspond to the active dimeric enzyme previously described in kidney and neoplastic hepatocellular tissue. In normal hepatocytes, the 73.5‐kDa protein represents 50% of the total GGT‐immunoreactive protein, contrast to kidney, where this band contains less than 4% of the GGT protein. The kinetics of expression of the 73.5‐kDa protein upon induction of GGT activity in hepatocytes, as well as in culture turnover studies, suggests that this protein is a precursor form of the active enzyme, such as the described 78/79‐kDa single‐chain glycoprotein propeptide of GGT. It appears that in normal hepato‐cytes, this precursor is not processed to the same extent as in kidney or in hyperplastic bile ductular tissue.