Enterochromaffin cells in the rat gastrointestinal tract. Aspects of factors influencing quantification.

A quantitative study was made of the enterochromaffin (EC) cells, visualized with the Masson (slightly modified) and Falck-Hillarp techniques, in the rat gastrointestinal tract. Different factors influencing the quantification were analysed and the magnitude of methodological errors was estimated. The two histochemical techniques visualized the EC cells in different ways, influencing the quantification results. This means that a comparison of the quantitative results obtained by these techniques can only be made after correction by some factors. The frequency of EC cells is given as the number of cells both per mm3 mucosa (cellular density) and per segment of mucosa with a base of 1 mm2. The latter information takes into account both cellular density and mucosal thickness. The highest frequency of EC cells was found in the pyloric gland area of the stomach. On the border with the duodenum there was a marked decrease in this frequency and in the whole intestine the frequency was low, with only minor fluctuations of the mean values. The frequency was increased in the caecum, followed by a gradual decrease in the large intestine. The quantitative variation of the EC cells at the same gastrointestinal level was considerable, and was greater between animals than between serial sections within the same animal. The difference in EC cell frequency that was required to give significance was calculated. For quantitative studies the Masson method has some minor advantages over the Falck-Hillarp technique, as routine formalin-fixed deparaffinized sections can be used and no counterstaining is needed for the areal estimation.