Résumé
By means of the fluorescent histochemistry the small intense fluorescent (SIF) cells of the rat heart were identified under the fluorescent microscope, then the tissue containing these cells were prapared for electron microscopy. Ultrastracturally SIF cells were small in size and contained a lot of granules which can be distinguished into two types of electric density, and abundant number of mitocondria which appeared about 20 in each section of SIF cell at the nuclear level, and a large Golgi complex which consisted of 4-7 cisternae arranging in paralled array and some vesicles. Many single cisternae of rough endoplasmic reticulum were distributed in their cytoplasm. Adhesion zones and interdigitated processes were often observed between two SIF cells. Cholinergic nerves formed afferent synapses with SIF cells. SIF cells often occured near fenetrated capillaries. We found that the core of the granulated vesicles of some SIF cells were released into the perivascular space. These results indicated that SIF cells of the rat heart may have a local regulatory fnuction either as endocrinal or paracrinal cells.