Acute-phase behavior of factor VIII procoagulant and other acute-phase reactants in rabbits.

We measured the plasma concentrations of factor VIII procoagulant (FVIII:C) in rabbits in two laboratory models of inflammation and after injections of purified homologous interleukin 1 (IL-1). The mean FVIII:C activities 2-4 days following the intramuscular injection of turpentine were significantly elevated, as were the concentrations of fibrinogen and C-reactive protein (CRP). By contrast, rabbits given 50 ng of bacterial lipopolysaccharide intravenously developed increased levels of FVIII:C but not of fibrinogen or CRP. We then studied plasma levels of FVIII:C, fibrinogen, and CRP after injections of either form of purified rabbit IL-1. If the rabbits' temperatures were monitored, FVIII:C levels increased in a log dose-related manner. This effect was not seen unless the rabbits were restrained and was seen in restrained rabbits even if the temperatures were not monitored. Fibrinogen and CRP levels did not change after IL-1 injections. These findings demonstrate that FVIII:C is an acute-phase reactant as judged by its response to turpentine inflammation or endotoxin injections, and to injections of IL-1 in restrained rabbits. FVIII:C appears to be a more sensitive acute-phase reactant than either fibrinogen or CRP. Neither of the latter proteins responded to low-dose endotoxin injections nor to either form of purified homologous IL-1. The doses of IL-1 given did cause fever, neutrophil leukocytosis, and hypoferremia.