Electron microscopic classification of amine-producing endocrine cells by selective staining of ultra-thin sections.

Abstract

The argyrophil, argentaffin and chromaffin reactions were performed directly on ultra-thin sections for examination in the electron microscope. Glutaraldehyde fixation was appropriate for the argentaffin and chromaffin reactions; additional fixation with osmium tetroxide, however, caused impairment of these reactions. Fixation with formaldehyde, but not with glutaraldehyde, was adequate for the argyrophil reaction; post-fixation with osmium tetroxide did not affect this staining. At the light microscopic level the staining reactions were correlated with fluorescence histochemistry according to the method of Falck and Hillarp. The techniques described were used to study certain amine-producing endocrine cell systems: adrenal medullary cells and thyroid parafollicular cells of the mouse, gastric endocrine cells from the oxyntic gland area of the mouse, rat and rabbit. All these cells stained argyrophil. The adrenal medullary cells and one cell type in the oxyntic gland area of the rabbit were strongly argentaffin and chromaffin. The remainder of the cells were non-argentaffin and non-chromaffin but could be induced to give an argentaffin (and chromaffin) reaction after injection of the animals with l-3,4-dihydroxyphenylalanine or l-5-hydroxytryptophan, a treatment which is known to result in the accumulation of the highly reducing dopamine and 5-hydroxytryptamine, respectively, in these endocrine cells. Without exception the precipitates formed in all the staining reactions accumulated selectively over the secretory granules of the cells. The techniques described permit differential staining of consecutive ultra-thin sections for electron microscopic characterization of one and the same cell. They will provide information necessary for correlative studies of the stainable cells at the light and electron microscopic levels.