Different regulatory mechanisms for serum amyloid A and serum amyloid P synthesis by cultured mouse hepatocytes.

Regulation of the in vitro synthesis of the serum amyloid proteins A and P has been studied with hepatocyte cultures from CBA/J and C3H/HeJ mice. Liver cells were isolated by the collagenase perfusion technique and established for 48 h in the presence of fetal calf serum. Viable cells could then be maintained in the absence of serum for at least 72 h and in the presence of serum for up to 2 weeks. Serum amyloid A synthesis differed from serum amyloid P synthesis in three significant ways. 1) Serum amyloid A production was stimulated in the presence of fetal calf serum, whereas serum amyloid P was not; 2) serum amyloid A synthesis was increased 200% by monokine-rich macrophage supernatants while serum amyloid P was increased only 10 to 20%; 3) serum amyloid A synthesis was strikingly resistant to cycloheximide inhibition as compared with serum amyloid P and other liver proteins. It is concluded that the in vivo asynchrony of the acute phase serum amyloid A and serum amyloid P responses results at least in part from differences in regulatory mechanisms for their synthesis by hepatocytes.