[On an electron microscopic study of the juxtaglomerular special structure of the kidney. III. Epithelioid cells in the afferent arterioles].

Abstract

In the mouse and the rat, the epithelioid (juxtaglomerular) cells in the media of the preglomerular part of the afferent arteriole are relatively large cells which are rich in more or less osmophilic granules and are embedded in a framework of basement membranes. These membranes are here and there interrupted while the cell membranes are always continuous. The nuclei are ellipsoid and may be indented by the secretory granules; in some sections nucleoli are seen. The most striking structures of the epithelioid cells are the spherical or polymorphous secretory granules which have a smooth contour and are surrounded by a smooth single membrane. As a rule their content is flocculent; often it contains smaller inclusions that are more or less electron dense and sometimes of a complex structure. The rather pale mitochondria show the usual structure; they are abundant but frequently somewhat concealed between the generally much larger secretory granules. The Golgi apparatus is very well developped; Golgi elements (parallel lamellae, vacuoles and vesicles) may be seen several times in the same cell section. In two epithelioid cells a centriole has been found near the nucleus. Moreover the cytoplasm contains a very rich ergastoplasm (endoplasmic reticulum) and is plentifully supplied with ribosomes. Microbodies and multivesicular bodies are rare. On the other hand, fibrillar structures (myofibrils ?) are often present. The ultrastructure of the epithelioid cells suggests that they have an active metabolism and, according to all evidence (see discussion), a secretory function. The nature of the elaborated substance has not yet been defined.