Microscopic structure of pyloric epithelium of the cat.

The microanatomy of the glands in the mucous membrane of the mammalian stomach exhibits distinct structural features in different regions. Cardiac glands, in a narrow ring bordering the oesophageal orifice, consist of mucin-secreting cells only, whereas in the fundus and body of the stomach the glands contain chief (peptic) and parietal (oxyntic) cells as well, and are known as oxyntic or fundic glands, although they occupy a very much larger area than the fundus alone. In the distal part of the stomach a third type of gland-the pyloric-is present. Most of the histological, histochemical and ultrastructural studies on gastric mucosa have concentrated on the body region, in order to correlate form with function in chief and parietal cells. The pyloric mucosa has been relatively neglected, but it is an important element in gastric physiology and pathology. Apart from producing mucin, it acts as an endocrine gland secreting gastrin, 5-hydroxytryptamine, histamine and possibly other substances. There is ample evidence that enterochromaffin cells in many species secrete 5-HT (see Erspamer, 1961; Vialli, 1966) but the site of production of other substances is less certain. Some 'enterochromaffin-like' cells of pyloric mucosa (in the rat) have been shown to produce histamine (e.g. H'akanson, Lilja & Owman, 1967) and Solcia, Vassallo & Sampietro (1967) described in several species a non-enterochromaffin endocrine cell which they designated the G cell, speculating that it could possibly be the source of gastrin. There is an obvious need for more knowledge of these cell types. Furthermore, peptic ulceration of the stomach in man almost invariably occurs in mucosa of pyloric type, not in that of the body, and the predilection of pyloric mucosa as the site for these localized lesions has not yet been satisfactorily explained. The study of pyloric mucosa hardly needs further justification, and the present report concerns the cells of the epithelium of this region of the alimentary tract in the cat.