CHARACTERIZATION OF THE INTERSTITIAL-CELLS ASSOCIATED WITH THE SUBMUSCULAR PLEXUS OF THE GUINEA-PIG COLON

Interstitial cells associated with the submuscular plexus of the guine a pig colon were studied by electron microscopy and by light microscop ic wholemount stretch preparations. Their cytoplasmic features are sim ilar to those of fibroblasts and they contain a well-developed Golgi a pparatus, granular endoplasmic reticulum and many mitochondria. Interm ediate filaments are abundantly distributed throughout the perinuclear region and processes. Numerous caveolae, a basal lamina and subsurfac e cisterns are observed on the cell membrane as in smooth muscle cells . The most characteristic feature of this cell type is the existence o f many large gap junctions that interconnect these cells to each other and with the smooth muscle cells. Nerve varicosities containing synap tic vesicles are observed in close apposition with cells of this type. Whole-mount preparations stained by the zinc iodide-osmic acid method and by vimentin immunohistochemistry clearly demonstrated the stellat e form of these gap junction-rich cells and suggested that they corres pond to the interstitial cells of Cajal.