ULTRASTRUCTURAL CHARACTERIZATION OF INTERSTITIAL-CELLS OF CAJAL IN THE RAT SMALL-INTESTINE USING CONTROL AND WS WS MUTANT RATS/

Interstitial cells in the myenteric plexus and the deep muscular plexu s of the small intestine of the c-kit mutant rats (Ws/Ws) and their no rmal siblings (+/+) were studied. c-Kit immunoreactivity was detected in two regions corresponding to the myenteric plexus and the deep musc ular plexus in the jejunum of +/+ rats, while no immunoreactivity was detected in Ws/Ws rats. Using electron microscopy, two types of gap ju nction-forming interstitial cells were found in association with the m yenteric plexus in +/+ rats: one type characterized by a typical fibro blastic ultrastructure, and the other characterized by numerous mitoch ondria and less electron-dense cytoplasm. Since the latter were greatl y reduced in Ws/Ws rats, it was suggested that these cells correspond to c-kit-expressing cells, i.e. interstitial cells of Cajal in the mye nteric plexus region. In contrast, two types of interstitial cells in the region of the deep muscular plexus were observed with no differenc e between +/+ and Ws/Ws rats. Probable interstitial cells of Cajal in this region were characterized by a basal lamina and numerous caveolae as well as large gap junctions that interconnect with each other and with the smooth muscle cells. We concluded that interstitial cells of Cajal in the rat intestine are heterogeneous in ultrastructure, c-kit dependency in the cell maturation, and functional role.