Identification of EC cells in the human intestine: a comparative study between immunohistochemical and silver impregnation techniques.

Selective immunohistochemical identification of enterochromaffin (EC) cells in the human duodenum and colon has been carried out, using a highly specific rabbit antiserotonin serum and the unlabeled peroxidase-antiperoxidase complex (PAP) technique. The sensitivity of the reaction, and morphology of the cells, were compared with those of the argentaffin or argyrophil reactions on the same sections at the light microscopic level. All argentaffin cells were argyrophil and PAP positive, but a small number of PAP-positive cells were neither argentaffin nor argyrophil. In addition, a few EC cells stained by the PAP method were shown to be argyrophil but not argentaffin. The PAP method permitted the clear morphological identification of the entire cell, particularly its cytoplasmic processes, whereas both the argentaffin and argyrophil reactions were basically seen in the basal regions of the cells and often failed to demonstrate the cytoplasmic processes. These findings indicate that the immunohistochemical method is more sensitive and advantageous than silver impregnations for the selective demonstration of EC cells.