What is the significance of JGA in kidney?
The juxtaglomerular apparatus (JGA), consisting of the glomerular afferent and efferent arterioles and the specialized tubular epithelial cells called the macula densa, plays a central role in the regulation of glomerular hemodynamics and renin release.
What role do the JG cells play in GFR?
Extraglomerular mesangial cells are located in the junction between the afferent and efferent arterioles. These cells have a contractile property similar to vascular smooth muscles and thus play a role in “regulating GFR” by altering the vessel diameter.
What is JG cells of kidney?
Juxtaglomerular cells (JG cells), also known as granular cells are cells in the kidney that synthesize, store, and secrete the enzyme renin. They are specialized smooth muscle cells mainly in the walls of the afferent arterioles (and some in the efferent arterioles) that deliver blood to the glomerulus.
Are Juxtaglomerular cells in the macula densa?
Macula densa cells are strategically positioned in the juxtaglomerular apparatus with their apical membrane exposed to the tubular fluid, whereas their basilar aspects are in contact with cells of the mesangium and the afferent arteriole (Figure 1A).
What is the function of macula densa?
Macula densa (MD) cells are chief cells within the kidney, playing key sensory and regulatory functions in the maintenance of body fluid, electrolyte homeostasis, and blood pressure.
How JGA is regulating the kidney function?
Regulation involving Juxtaglomerular Apparatus: In kidneys, the JGA acts as a Multi Hormonal renin angiotensin aldosterone system (RAAS). When the glomerular blood flow decreases JG cells activates and releases renin. Renin converts angiotensin in blood to angiotensin 1 and further to angiotensin 2.
What do macula densa cells respond to?
It is thought that the macula densa cells are sensory cells that respond to the sodium concentration in the fluid within the distal tubule and, perhaps, to the rate of fluid flow past them.
What do macula densa cells detect?
Macula densa cells detect changes in luminal sodium chloride concentration through a complicated series of ion transport–related intracellular events.
How does macula densa cause renin release?
It also results in the release of renin, which, through the renin–angiotensin system, causes constriction of the efferent arterioles, which ultimately increases hydrostatic pressure in the glomerulus. The process triggered by the macula densa helps keep the GFR fairly steady in response to varying artery pressure.
How does macula densa release renin?
Macula-Densa Control of Renin Release The macula densa participates in the regulation of renin release from juxtaglomerular granular cells. Renin secretion depends on NaCl delivery to and reabsorption by the macula-densa cells at the end of the TAL.
What do JG cells secrete?
renin
The juxtaglomerular cells secrete renin, and as specialised smooth muscle cells surrounding the afferent arteriole also have the capacity to affect the perfusion of the glomerulus.
What do macula densa cells secrete?
Macula-densa cells may signal granular cells to inhibit renin release by secreting adenosine and/or ATP across the basolateral membrane in response to increased sodium delivery [96, 101, 102].
Where are macula densa cells located in the kidney?
Macula densa cells in the distal nephron, according to the classic paradigm, are salt sensors that generate paracrine chemical signals in the juxtaglomerular apparatus to control vital kidney functions, including renal blood flow, glomerular filtration, and renin release.
How is renin released from the macula densa?
Second, prostaglandin activates prostaglandin-sensitive specialized smooth muscle cells of the renal afferent arterioles, juxtaglomerular cells (JG cells), to release renin into the bloodstream. The JG cells can also release renin independently of the macula densa.
How are prostaglandins released from the macula densa?
Function. Second, macula densa cells release prostaglandins, which triggers granular juxtaglomerular cells lining the afferent arterioles to release renin into the bloodstream. (The juxtaglomerular cells can also release renin independently of the macula densa. They are also triggered by baroreceptors lining the arterioles,…
How is GPR91 activated in macula densa cells?
GPR91 activation in macula densa cells is connected to the same signaling cascade as salt sensing; namely, the activation of p38 and ERK1/2 MAP kinases, COX-2, and the synthesis and release of PGE 2-triggered renin exocytosis.