Immunohistochemical markers for enterochromaffin-like (ECL) cells of the rat stomach

Several different markers have been used for the immunocytochemical visualization of enterochromaffin-like (ECL) cells. The ECL cell specificity of some of these markers is, however, not yet established. In the present study several proposed ECL cell markers were compared using double immunostaining. Immunoreactive (IR) histidine decarboxylase (HDC) was restricted to ECL cells. IR-calbindin D28k was also restricted to ECL cells, but was lacking in a subpopulation of the cells; vesicular monoamine transporter 2 (VMAT-2) was found in both ECL cells and in an additional endocrine cell population, tentatively identified as A-like cells; IR-pancreastatin was found in ECL cells, somatostatin cells and presumed A-like cells. Since the expression of ECL cell markers may depend on the activity state of the cells, one group of rats received high doses of the acid blocker omeprazole in order to induce high ECL cell activity, and another group of rats were fasted for 24 hours in order to reduce ECL cell activity. HDC and calbindin D28k immunostaining became markedly stronger in omeprazole-treated rats and weaker in fasted rats; VMAT-2-IR changed less and pancreastatin immunostaining tended to decrease upon ECL cell activation, presumably due to degranulation. Thus, the expression not only of HDC, but also of other ECL cell markers, including IR-calbindin D28k, is dependent upon ECL cell activity. Inactive ECL cells may escape detection using HDC or calbindin D28k.