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The endocrine apparatus of the kidney
Medical expert of the article
Last reviewed: 04.07.2025
The endocrine apparatus of the kidneys includes:
- juxtaglomerular apparatus;
- interstitial cells of the medulla and nephrocytes of the collecting ducts;
- kallikrein-kinin system of nephrocytes of distal convoluted tubules;
- APUD system cells.
Juxtaglomerular apparatus
It is a differentiated cellular complex located in the region of the vascular pole of the glomerulus between the afferent and efferent glomerular arterioles and the closely adjacent parts of the distal tubule.
Juxtaglomerular apparatus cells
- Granular cells are located in the wall of the afferent glomerular arteriole and secrete renin.
- Cells of the macula densa. Located in the area of the distal convoluted tubule at the point of its contact with the granular cells of the afferent glomerular arteriole. Cells of the macula densa react to the sodium chloride content in the lumen of the convoluted distal tubule, transmitting a signal to the smooth muscle cells of the afferent arteriole.
- Gurmagtig cells (lacis cells). They are located between the glomerular arterioles and have direct contact with the mesangium.
- Glomerular mesangial cells.
Electron microscopy data confirm the close relationship of granule cells, macula densa cells, ash cells, and glomerular mesangial cells with each other and with smooth muscle cells.
Functions of the juxtaglomerular apparatus
The physiological purpose of the juxtaglomerular apparatus is to control the amount of glomerular filtration and renin secretion. At present, the relationship between changes in the volume of extracellular fluid and renin secretion has been clearly established. Thus, with an increase in the volume of extracellular fluid, the delivery of sodium and chlorides to the distal tubules increases. In response, the reabsorption of sodium chloride in the distal tubules increases, and this becomes a signal that inhibits the release of renin. With a decrease in the volume of extracellular fluid, the delivery of sodium chloride to the distal tubule decreases and the secretion of renin increases.
On the other hand, the juxtaglomerular apparatus plays an obvious role in regulating the SCF. The glomerular blood flow depends on the concentration of sodium chloride in the macula densa through a mechanism known as tubuloglomerular feedback. Its essence is that with an increase in the concentration of sodium chloride in the macula densa, there is a decrease in glomerular blood flow and SCF due to the release of renin and local formation of angiotensin II, causing constriction of the afferent glomerular arteriole. This signal-effector system allows the kidneys to regulate sodium reabsorption and perform vasoconstriction at the level of an individual nephron.
Interstitial cells of the medulla of cells
Three types of interstitial cells are found in the renal medulla, but only cells with fatty inclusions have hormonal activity, containing up to 70% prostaglandins, which have a powerful vasodilating and natriuretic effect. The concentration of fat granules in cells increases toward the apex of the renal papilla.
Kallikrein-kinin system of the kidneys
It is represented by nephrocytes of the distal tubules, in which the enzyme kallikrein is formed. After secretion into the lumen of the distal tubule, it interacts with kininogen, resulting in the formation of biologically active compounds - kinins. Just like prostaglandins, kinins have pronounced vasodilatory and natriuretic properties.
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