In-vitro synthesis of alpha 2-macroglobulin by human gingival fibroblasts

Cells from explants were cultured in the presence of [L-35S]-methionine for 24 h. Cultures containing cycloheximide or cultures frozen immediately after addition of labelled methionine served as controls. The medium was removed and, after washing, cells were disrupted by repeated freezing and thawing. Synthesis of alpha 2-macroglobulin (alpha 2-M) was evaluated by autoradiography of the SDS-PAGE patterns obtained with the culture medium, and by autoradiography of the crossed immunoelectrophoretic patterns obtained with both the cell extract and the culture medium. There was incorporation of labelled methionine in newly-synthesized alpha 2-M. No autoradiographic bands were found in the frozen preparations, and there was a progressive inhibition of globulin synthesis in the presence of increasing concentrations of cycloheximide. This synthesis of alpha 2-M by human gingival fibroblasts may explain the presence of free alpha 2-M in gingival fluid and might be of significance in the control of proteolysis during gingivitis and periodontitis.