[Functional morphology of the large intestinal mucosa of horses (Equus przewalskii f. caballus) with special regard to the epithelium].

The mucous membrane of the caecum and colon ascendens of adult horses was first studied using light and transmission electron microscopy. In the surface epithelium there was an inconspicuous constellation of organelles, otherwise there was a lot of mitochondria as a source of energy for absorptive performances. Moreover, enlarged intercellular spaces exist as an indication of an increased uptake of water and electrolytes. In the basal region of Lieberkühn's crypts there were single enteroendocrine cells and numerous granules in the apical epithelial cytoplasm. The functional meaning of these granules is contrarily discussed in the literature. There was no epithelial activity of alkaline phosphatase. Against that a small positive reaction of adenosine triphosphatase was observed at the lateral plasmalemata of the epithelial cells. The sense of these findings with regard to the transport of substances in the equine large intestine is discussed.