Identification and characterization of enterochromaffin cells with different staining techniques

The staining characteristics of the enterochromaffin cell system in the human and rat gastrointestinal tract were studied with 3 histochemical procedures--the Masson method, formaldehyde-induced fluorescence (FIF), and immunocytochemical techniques using both monoclonal and polyclonal serotonin antisera. A simple modification of the Masson technique is described and compared with several other modifications of the same technique. The specificities of the 2 antisera were examined with regard to serotonin and other monoamines and their albumin conjugates, monoamine precursors and metabolites, and also to serotonin-related substances. In the intestine, with very few exceptions the same cells reacted positively with the 3 staining methods, but often serotonin immunoreactivity was observed in larger cytoplasmic areas than the other 2 staining reactions. In the antral mucosa, a cell population with the same staining characteristics as mentioned above was seen, but 2 further cell populations were identified--one displaying FIF-argentaffin reactions but no serotonin immunoreactivity, and the other showing the opposite characteristics. At immunostaining, a discrepancy in the staining results between the 2 antisera was noted--a larger number of antral serotonin immunoreactive cells being demonstrated with the polyclonal than with the monoclonal antiserum; this discrepancy disappeared when the polyclonal antiserum was pretreated with C-terminal tetragastrin. A minor discrepancy in the number of stained cells was still observed between the use of immunostaining with monoclonal or with tetragastrin-pretreated polyclonal antiserum, and the use of the FIF-argentaffin reactions. The reason for this discrepancy is unclear.