Fat storing cells (FSC) of rat liver synthesize and secrete fibronectin. Comparison with hepatocytes.

Fat storing cells (FSC) of rat liver were isolated and kept in culture for up to 2 weeks. Freshly isolated cells and cells in culture were characterized functionally (vitamin A content) and morphologically. Their synthetic capacity for fibronectin was studied quantitatively by ELISA-measurement and qualitatively by biosynthetic labeling, immunoprecipitation and SDS-PAGE analysis. The synthesis product and the kinetics of the synthesis and secretion were compared with those obtained from culture of hepatocytes. FSC were shown to synthesize and secrete fibronectin under the culture conditions used. No fibronectin synthesis was detected during the first 3 days of culture. Thereafter the synthesis increased continuously up to 2600 ng/24 h/100 micrograms cell protein. The molecular weight of fibronectin synthesized by fat storing cells seems to be the same as the one synthesized by hepatocytes, but the secretion proceeds faster in hepatocytes than in FSC. No differences between the two molecules were observed when both cell populations were treated with tunicamycin (TM), an antibiotic which inhibits the N-glycosylation of the primary translation product.