Biosynthesis of the third (C3), eighth (C8), and ninth (C9) complement components by guinea pig hepatocyte primary cultures.

In the present report guinea pig hepatocyte primary cultures were established in order to study the synthesis of the eighth (C8) and ninth (C9) complement component. As reference-protein, the third complement component (C3) was measured antigenetically and hemolytically. Synthesis of C8 and C9 was determined by means of the hemolytic activity of the culture supernatant harvested every 24 h during a 6-day incubation period in vitro. The data to be reported demonstrated that the hepatocytes are able to synthesize spontaneously and secrete C8 and C9; in their culture medium a hemolytic activity of about 15-25 X 10(8) em/10(6) cells/24 h for C8 and of 25-90 x 10(8) em/10(6) cells/24 h for C9 were found. The same hepatocyte cultures produced 2500-6000 micrograms/10(6) cells/24 h of C3. Hemolytic C3 activity was also found in the culture media. The synthesis of C8 and C9 could be reversibly inhibited by addition of 30-50 micrograms cycloheximide per ml of culture medium. The kinetics of synthesis show a slight decrease after the first day of culture and a recovery in the following days up to a rate that is two- to threefold higher than that of the first day. The data suggest that hepatocytes could contribute to the production of C8 and C9 present in the plasma.