The equine colonic mucosal granular cell: identification and X-ray microanalysis of apical granules and nuclear bodies.

The granular columnar epithelial cell of the equine dorsal large colon has been studied by transmission electron microscopy and X-ray microanalysis. Particular attention was focused on nuclear bodies commonly observed as central clusters of spherical, electron-dense inclusions within the nucleus. Ultrastructural morphology as well as X-ray microanalysis spectra reveal great similarity between colonic nuclear bodies and the numerous small granules of the apical cytoplasm in these epithelial cells. X-ray spectra of these cells were distinct from those of goblet cell mucous granules and mast cell granules. No evidence was found indicating transit of nuclear body granules through the nuclear envelope, or for morphologic association with the nucleoli. Of the diverse types of nuclear bodies previously reported in other species, equine colon nuclear bodies morphologically most closely resemble those seen in rabbit adenohypophysis. Colon epithelial cell nuclear bodies are likely identical to equine small intestine nuclear bodies, but their origin and role remain unknown.