A GROWTH INHIBITOR OF RAT HEPATOCYTES SYNTHESIZED BY A RAT HEPATOMA-CELL LINE, FF101

A rat hepatoma cell line, FF101, established in serum-free, protein-fl ee medium synthesizes a growth inhibitor of adult rat hepatocytes in p rimary culture. Gel filtration of FF101-conditioned medium disclosed t wo peaks of growth inhibitory activity with the molecular sizes over 2 00 kDa and smaller than 10 kDa. The growth inhibitor of smaller molecu lar size was tentatively designated as FF-GI. The DNA synthesis of rat hepatocytes was inhibited by FF-GI. The inhibitory activity of FF-GI was abolished by treatments with trypsin, dithiothreitol and heating a t 100 degrees C for 30 min, although it was stable against acid treatm ent and heating at 100 degrees C for 5 min. These results indicate tha t FF-GI may be a novel growth inhibitor of adult rat hepatocytes.