Induction of glutamine synthetase in periportal hepatocytes by cocultivation with a liver epithelial cell line.
Cocultures of periportal, glutamine synthetase-negative (GS-) hepatocytes with endothelial cells of human veins or epithelial cells of rat liver (clone RL-ET-14) were established for testing whether GS could be induced in the hepatocytes by interactions between the different cell types. While GS activity in endothelial cells was below detection level that of RL-ET-14 cells decreased from 62 mU/mg (24 h) to 38 mU/mg (168 h). During cocultivation with endothelial cells no change in the low GS activity could be detected. In contrast, when periportal hepatocytes were cocultured with RL-ET-14 cells, GS activity of the cocultures increased continuously from 26 mU/mg (24 h) to 56 mU/mg during cultivation for 168 h. Immunocytochemical staining of the cocultures for GS showed that this rise of GS activity was associated with an increase of GS level in the periportal hepatocytes and a decrease in the RL-ET-14 cells. Correspondingly, cultivation of periportal hepatocytes with media conditioned by the RL-ET-14 cells led to an increase in GS activity which, however, remained below that of cocultures, while conditioned medium of hepatocytes resulted in a decrease of GS activity in pure cultures of RL-ET-14 cells. "Separated" cocultures, where hepatocytes and RL-ET-14 cells reached each other only at the border of a circular area, demonstrated that induction of GS was highest in the marginal hepatocytes and lowest in those located in the center indicating that besides (a) soluble factor(s) other kinds of cell-cell interactions might be responsible for full induction of GS expression in periportal hepatocytes.
Schrode
W
W
Physiologisch-Chemisches Institut der Universität, Tübingen/Bundesrepublik Deutschland.
Mecke
D
D
Gebhardt
R
R
D000818:Animals; D002460:Cell Line; D003470:Culture Media; D004730:Endothelium, Vascular / Q000166:cytology; D004790:Enzyme Induction; D004847:Epithelial Cells; D004848:Epithelium / Q000201:enzymology; D005974:Glutamate-Ammonia Ligase / Q000096:biosynthesis*; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D003470:Culture Media; D005974:Glutamate-Ammonia Ligase