ON THE MORPHOLOGY OF THE JUXTAGLOMERULAR APPARATUS

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Abstract
The structure of the juxtaglomerular apparatus in the normal rat kidney has been investigated on the basis of serial sections. By this technique it has been possible to build three dimensional models of this part of the nephron. It has been confirmed that the efferent and afferent vessels near the glomerulus are placed in close relation to those parts of the distal tubule which are situated before and after the macula densa respectively. The dependence of the content of the epithelioidcells and the juxtaglomerular granules in the afferent vessel on the distance between the glomerulus and the surface of the kidney is confirmed. It has seen that afferent vessels, placed at the same distance from the surface, may contain a varying number of epithelioid cells and juxtaglomerular granules. A similar individual variation in the number of cells was apparent in the macula densa as well as in the cell group of Goormaghtigh (the lacis-cells). It was demonstrated that the highest number of cells in the macula densa is found subcapsular, whereas the cell group of Goormaghtigh is largest in the juxtamedullary region. In a position corresponding to that of the epithelioid cells in the vessels as seen in conventional preparations, somewhat different structures appear in the freeze-dried tissue. By the freeze-drying technique, a new cell type was noticed in the distal tubule, selectively placed in or close to the macula densa. The characteristics of the cell are: a big nucleus and a light cytoplasm in which are seen numerous granules close to the nuclear membrane. In the freeze-dried tissue, the height of the cells in the macula densa varied according to the degree of the dilation of the distal tubular, showing the better preservation of the functional aspects of the nephron with the use of this preparation.