PROTEIN KINASE-C-ALPHA, KINASE-C-BETA AND KINASE-C-GAMMA SUBSPECIES IN BASAL GRANULATED CELLS OF RAT DUODENAL MUCOSA

Protein kinase C [cPKC: alpha, beta (beta(I), beta(II)), gamma], a Ca2 +- and phospholipid-dependent enzyme, has been thought to play a criti cal role in the synthesis and secretion of gut hormones in gastrointes tinal mucosa. However, the localization of PKC has not yet been clarif ied at the cellular level in the gastrointestinal epithelium. The pres ent study was made to identify cPKC-containing cells immunohistochemic ally in the rat duodenal epithelium by light and electron microscopy a nd by confocal laser scanning microscopy. Special attention was paid t o the demonstration of cPKC in basal granulated cells. By light micros copy, some duodenal epithelial cells were demonstrated to be immunopos itive for PKC alpha-, beta- and gamma-subspecies. Their distribution a nd incidence were almost similar to those of cells stained by the silv er impregnation method of Grimelius. By electron microscopy, profiles of secretory granules were found at the basal region of the PKC-immuno positive epithelial cells. When the cells were double-immunostained fo r gastrin, serotonin or somatostatin and for PKC alpha-, beta- or gamm a-subspecies, these gut hormones and PKC subspecies were shown to colo calize as examined by confocal laser scanning microscopy. These findin gs show that cPKC (alpha, beta, gamma) is present in basal granulated cells such as G-, EC- and D-cells, presumably playing some important r ole in regulation of gut hormones, including their synthesis and/or se cretion.