Metaplasia of smooth muscle cells into juxtaglomerular cells in the juxtaglomerular apparatus, arteries, and arterioles of the ischemic (endocrine) kidney. An ultrastructural-cytochemical and autoradiographic study.

Partial ligation of the aorta between the renal arteries induces marked atrophy of the cortical tubules of the left (endocrine) kidney with a remarkable increase in the number and granularity of hypersecretory juxtaglomerular cells (JGC), which are found not only at the glomerular pole of arterioles but also in the walls of arteries and arterioles far removed from the glomerulus. Typical vascular smooth muscle cells (SMC), in which secretory granules appear, show a concomitant development of their Golgi complex and rough endoplasmic reticulum, with a gradual decrease in the number of their filaments. Microtubules also appear in the Golgi area. Thiery's periodic acid-thiocarbohydrazide-silver proteinate technique demonstrates that in these "intermediate" cells, as in mature JGC, the amount of glycogen is greater than in SMC. The newly-developed secretory granules of intermediate cells are stained by phosphotungstic acid at a low pH, as are the mature granules of JGC, an indication that both types contain glycoproteins. Light and electron microscopic autoradiography reveal that both JGC and "intermediate" cells of the vascular wall do not incorporate radioactive thymidine (injected during the 10-day observation period). Thus, they develop by metaplasia of preexistent SMC. In control kidneys, radioactive thymidine is practically never incorporated into the nuclei of SMC but is found in a few glomerular and tubular cells of all zones except the papilla.The endocrine kidney shows virtually no reactive nuclei in vascular SMC, glomeruli, or tubular cells of the outer cortex. Thymidine is incorporated into practically all nuclei of the straight portion of proximal tubules and into about half the nuclei of all medullary tubular cells including the papilla.

Ultrastructural cytochemistry of the ischemic (endocrine) kidney.

Partial ligation of the aorta between the renal arteries induces marked atrophy of the cortical tubules (including the macula densa) of the left (endocrine) kidney with a remarkable increase in the number and granularity of hypersecretory juxtaglomerular granulated cells (JGC) which are found not only at the glomerular pole of arterioles but also in the walls of arteries and arterioles far removed from the glomerulus. Staining of fine sections of Araldite-embedded endocrine kidneys according to the periodic acid-thiocarbohydrazide-silver proteinate technique of Thiery reveals abundant glycogen in the JGC and less in the blood vessels and tubules. Juxtaglomerular granules are argentaphobic, but their rim is positively stained when ultrathin sections of glutaraldehyde-fixed, glycol methacrylate-embedded kidneys are exposed to phosphotungstic acid at a low pH. A positive reaction is also shown by the cell coat and lysosomes of JGC as well as by the thickened basal lamina, cell coat, cytosomes, and cytosegresomes of the atrophic tubules. Atrophy is most pronounced in the proximal convoluted tubules, which lose their apical microvilli, their basal infoldings and the majority of their mitochondria and cytosomes.