Induction of the acute-phase serum protein SAA requires both RNA and protein synthesis.

SAA is a normal acute-phase serum protein which has been identified by its cross-reaction with antibodies to the amyloid A fibril protein, AA, that is associated with secondary amyloidosis. The induction of SAA by bacterial lipopolysaccharide (LPS) has been studied with 3 inhibitors of protein synthesis: cycloheximide, actinomycin D, and galactosamine. Each of the 3 agents when administered simultaneously with LPS completely abolishes induction of SAA for at least 6 h. They are all significantly effective when given 1.5 h after LPS but 3 h after LPS the inhibitory effect of actinomycin D on SAA induction is markedly reduced. Cycloheximide alone can also induce significant concentration of SAA, but a longer time is required than for LPS. Thus it appears that the acute-phase SAA response is characterized by both RNA and protein synthesis which is initiated by the acute-phase inducing agent and which precedes the appearance of elevated SAA concentrations in the serum.