From the Guidelines
The juxtaglomerular apparatus is composed of juxtaglomerular cells, macula densa, and extraglomerular mesangial cells.
Components of the Juxtaglomerular Apparatus
- Juxtaglomerular cells: specialized smooth muscle cells that produce and secrete renin, an enzyme that initiates the renin-angiotensin-aldosterone system 1.
- Macula densa: a group of specialized epithelial cells that sense changes in sodium chloride concentration and send signals to the juxtaglomerular cells to adjust renin release, as decreased chloride delivery in the tubules to the macula densa triggers renin release from the juxtaglomerular apparatus 1.
- Extraglomerular mesangial cells: provide structural support and help regulate blood flow. The juxtaglomerular apparatus plays a crucial role in regulating blood pressure and electrolyte balance, and its dysfunction can lead to various clinical conditions, including hypertension and kidney disease.
From the Research
Components of the Juxtaglomerular Apparatus
The juxtaglomerular apparatus (JGA) is a complex structure that plays a crucial role in regulating glomerular hemodynamics and renin release. The components of the JGA include:
- The macula densa, which is a specialized tubular epithelial cell that senses changes in tubular NaCl concentration 2, 3, 4, 5
- The glomerular afferent and efferent arterioles, which are involved in the regulation of glomerular blood flow 2
- The juxtaglomerular cells, also known as epithelioid cells, which are located in the walls of the afferent and efferent arterioles and are responsible for the synthesis and release of renin 3, 6
- The Goormaghtigh cells, which are located in the extraglomerular mesangium and are thought to play a role in the regulation of renin release 6
- The extraglomerular mesangium, which is a group of cells that surrounds the glomerulus and is involved in the regulation of glomerular function 4
Functional Relationships Between Components
The components of the JGA work together to regulate glomerular hemodynamics and renin release. For example:
- The macula densa senses changes in tubular NaCl concentration and triggers a signal transduction cascade that involves the synthesis of nitric oxide (NO) 4, 5
- The NO produced by the macula densa cells diffuses to the glomerular arterioles, where it causes vasodilation and increases glomerular blood flow 5
- The juxtaglomerular cells sense changes in glomerular blood pressure and release renin, which triggers the activation of the renin-angiotensin system 2, 3