Deplasticizing or etching of epoxy sections with different concentrations of sodium ethoxide to enhance the immunogold labeling.

The study's purpose was to obtain improved "deplasticizing" of epoxy sections for immunoelectron microscopy. Epoxy-embedded renal swine tissue with immune complex deposits was used. Ultrathin sections were mounted on uncoated grids or on carbon-stabilized formvar grids. The sections were exposed to different concentrations of sodium ethoxide, and they were subjected to immunogold labeling with anti-IgG. Etching with > or =8% of saturated solution gave completely deplasticized sections. Sections etched with 2-4% solution were only partly deplasticized, but these sections were detached if mounted on uncoated grids, and the yields of immunolabeling were significantly decreased compared with the deplasticized ones. Sections exposed to < or =1% solution were not detached from the uncoated grids. Double-sided labeling of uncoated sections etched with 1% solution yielded approximately the same immunolabeling as for the completely deplasticized formvar-supported sections, and they gave better ultrastructural preservation of the tissue. We have established that etching epoxy sections on non-supported grids with a diluted solution of sodium ethoxide may be preferable for immunoelectron microscopy.