Methylprednisolone affects inhibitors of the complement and the contact systems; functional and immunochemical studies on α2-macroglobulin and C1 inhibitor

Abstract

The effects of methylprednisolone sodium succinate (MP) on main inhibitors of the classical pathway of complement and on the contact system were studied in citrated pool plasma. Endotoxin (2·10 9 ng/l,lipopolysaccharide B, E. coli 026: B6 Difco Laboratories, Detroit, Michigan, USA) and/or MP in doses of 0.1, 1, 5 and 10 mg/ml were incubated with plasma at 37°C. Plasma samples were obtained at timed intervals up to 24 hours for determination of Cl inhibitor (Clinh) and α 2-macroglobulin ( α 2M) values using both functional and immunochemical assays. Plasma containing endotoxin without MP revealed decreases of Clinh and α 2M values after 12 hours. Addition of MP in high doses (10 mg/ml) gave an additive effect on the endotoxin-induced decreases of Clinh and α 2M values, evident 1 and 12 hours after the beginning of incubation, respectively. When MP alone was added to plasma (5 and 10 mg/ml) also significant decreases in Clinh and α 2M values were seen. MP in low doses (0.1 and 1 mg/ml) did not either influence the endotoxin-induced changes in the protease inhibitor functions, or induce significant changes in Clinh and α 2M values when incubated in plasma without endotoxin. This study demonstrates that MP in high doses induces marked decreases in plasma Clinh and α 2M inhibitory functions and that MP has an additive effect on the endotoxin-induced decreases of these inhibitors.