Effects of cytokines and growth factors on phosphorylated fetuin biosynthesis by adult rat hepatocytes in primary culture.

Recently, we showed that a 59 kDa non-phosphorylated sialoprotein purified from rat bone matrix is the rat counterpart of bovine fetuin and human alpha 2-HS glycoprotein and that fetuin synthesized and secreted by adult rat hepatocytes in primary culture is mostly phosphorylated (phosphofetuin), though fetuin is known to contain no phosphorus. Here we report that the rate of synthesis of phosphofetuin by hepatocytes in culture was reduced by inflammatory cytokines such as human interleukin (hIL)-6, human tumor necrosis factor-alpha and hIL-1 alpha, but dose-dependently stimulated by growth factors of hepatocytes, such as hepatocyte growth factor (HGF)/scatter factor (SF), epidermal growth factor and insulin, as determined by metabolic labeling and Northern blot analysis using cDNA for rat fetuin as a probe. We also showed that administration of HGF/SF stimulated gene expression of rat fetuin in vivo.