Effect of endogenous pyrogen, corticosteroids and inhibitors of prostaglandins and leukotrienes on the plasma concentrations of haptoglobin and fibrinogen in rats.

Injections of endogenous pyrogen (EP) in normal rats significantly increased plasma concentration of haptoglobin and fibrinogen while in adrenalectomized animals the same treatment was ineffective. Nevertheless when cortisone was injected simultaneously with EP into adrenalectomized rats the responses of fibrinogen and haptoglobin were restored. These results suggest that biosynthesis of fibrinogen and haptoglobin is corticosteroid-dependent. Inhibition of the cyclo-oxygenase pathway with ibuprofen or the lipoxygenase pathway with BW755C had no effect on the increase of plasma fibrinogen or haptoglobin levels stimulated by either EP or endotoxin. These data indicate that neither prostaglandins nor leukotrienes are involved in the production of these acute phase reactants induced by either stimulus.