Grocott kit is used in histology for visualization of argentaffin structures. For diagnostic purposes, it is mostly used for impregnating basal membranes and fungi using silver. The staining procedure is similar to the P.A.S. staining, however, the target structures are of more intense and
stronger contrast after staining with the Grocott kit. The section is treated with the periodic acid solution used to oxidize 1,2-glycols to aldehydes.
During incubation in methenamine-silver-borate working solution, aldehydes are reduced to primary alcohols with simultaneous reduction of silver ions to elementary silver (dark brown to black in color). This is followed by toning the section with gold chloride solution that additionally improves staining intensity of target structures, and it removes non-specific staining. Excessive unbound silver-gold bonds is removed by rinsing the section with sodium thiosulfate solution. Finally, the sections are exposed to Fast Green F.C.F. dye that stains background structures green; that in turn creates clear and visually rich contrast to target structures (brown to black in color).
This is new and improved formulation for Grocott staining. Kit is stable at room temperature, do not store at lower temperature!