IDENTIFICATION OF THE INTERSTITIAL-CELLS OF CAJAL

Observation of whole-mount stretch preparations using the zinc-iodide- osmic acid method reveals a wide variety of interstitial cells in diff erent tissue layers of the guinea-pig small intestine. And a subsequen t electron microscopic examination and survey of references makes clea r that the interstitial cells of Cajal (ICC) depicted in original draw ings of Cajal are heterogeneous and correspond to different types of i nterstitial cells. The myenteric ICC are characterized by long dichoto mous branching processes which constitute cellular networks independen t from the nerve plexus and form many gap junctions at their tips. The ir ultrastructure is similar to that of fibroblasts and they have no b asal lamina. The myenteric ICC show strong immunoreactivity for viment in and the c-kit receptor, and probably correspond to the intestinal p acemaker cells. Within the circular muscle layer, ICC are represented by the cells that are closely associated with fine nerve bundles. The ICC have various shapes, ranging from bipolar to stellate, depending o n the running pattern of the nerve fibers that they are associated wit h. They show fibroblast-like ultrastructure and have no basal lamina. They form gap junctions with smooth muscle cells and are immunoreactiv e for vimentin. On the other hand, ICC associated with the deep muscul ar plexus described in the guinea-pig by Cajal could not be clearly id entified. However, it is suggested that the ICC in this location may c orrespond to glycogen-rich cells possessing a basal lamina. Although t hey show a fairly well-developed rough endoplasmic reticulum, Golgi ap paratus and immunoreactivity for vimentin, ICC of the deep muscular pl exus are probably specialized smooth muscle cells in nature.