Effects of iodipamide on human C3 and factor B in vitro.

The effects of iodipamide on C3 and factor B in normal human serum and in purified form have been examined by immunoelectrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Temperature-dependent changes in immunoelectrophoretic profiles have been observed; however, these are not the same as those obtained after treatment of normal human serum (NHS) with cobra venom factor Naja naja. Analyses of iodipamide-treated NHS and purified C3 and factor B by reducing SDS-PAGE indicate that no macromolecular changes have occurred in C3 and factor B that can be ascribed to proteolysis (i.e., activation). The changes observed in C3 and factor B, including loss of hemolytic activity, appear to be due to direct interactions between iodipamide and C3 and factor B. In the case of factor B, iodipamide treatment at 37 degrees C induces aggregation, which is reversible upon reduction with beta-mercaptoethanol.