the macula densa, a part of the distal convoluted tubule of the same nephron. juxtaglomerular cells, (also known as granular cells) which secrete renin.
What do the macula densa cells regulate and their role as part of the tubuloglomerular feedback loop?
These cells play a pivotal role in sensing changes in tubular fluid composition, generating and sending signals to the juxtaglomerular apparatus that control renal blood flow and GFR through tubuloglomerular feedback and renin release.
What is special about the cells in the macula densa?
The cells of the macula densa are sensitive to the concentration of sodium chloride in the distal convoluted tubule. As such, an increase in sodium chloride concentration would result in vasoconstriction of afferent arterioles, and reduced paracrine stimulation of juxtaglomerular cells.
How do granular cells help regulate blood pressure?
The juxtaglomerular cells, derived from smooth muscle cells, of the afferent arteriole secrete renin when blood pressure in the arteriole falls. Renin increases blood pressure via the renin-angiotensin-aldosterone system.
How does macula densa affect 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.
How does macula densa cause renin release?
Macula densa cells at the end of the thick ascending limb of Henle’s loop respond to low lumen [NaCl] by signaling to juxtaglomerular granular cells at the end of the afferent arteriole to increase renin secretion.
What do macula densa cells regulate?
Macula densa cells monitor intratubular salt concentrations to regulate renal blood flow via afferent arteriole constriction and dilation. The juxtaglomerular cells also contain renin granules, which can send out a wider signal to control vascular resistance through the renin-angiotensin-aldosterone pathways.
How does macula densa release renin?
The macula densa, in response to the change in the Na concentration in the distal tubules, signals the juxtaglomerular cells to release renin. Renin is stored in granules and the secretion is stimulated by the β-adrenergic response and cAMP augmentation.
What do granular cells do?
Granule cells are the smallest and most numerous type of neurons in the brain. They are involved in functions ranging from processing visual and motor information to learning and memory. Brain Bytes showcase essential facts about neuroscience.
What does macula densa release?
The macula densa mediates afferent arteriolar constriction by the release of adenosine, which acts via adenosine-1 receptors. Adenosine-1 receptors mediate vasoconstriction by G protein–coupled receptors.
How does macula densa increase GFR?
Reduced NaCl uptake via the NKCC2 at the macula densa leads to increased renin release, which leads to restoration of plasma volume, and to dilation of the afferent arterioles, which leads to increased renal plasma flow and increased GFR.
What is granular cell?
The granular cell is a large polygonal, oval, or bipolar cell with abundant, fine, or coarsely granular eosinophilic cytoplasm, and a small, pale-staining or vesicular nucleus eccentrically located in the cell (Fig. 4.47B and C).
Why is the macula densa called the macular densa?
The cells of the macula densa are taller and have more prominent nuclei than surrounding cells of the distal straight tubule (cortical thick ascending limb). The close proximity and prominence of the nuclei cause this segment of the distal tubule wall to appear darker in microscopic preparations, hence the name macula densa .
What triggers the release of renin 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 does pgpge2 work in macula densa cells?
PGE2 acts on EP2 and EP4 receptors in juxtaglomerular cells and causes renin release (Figure 1B). In addition to COX-2-derived prostaglandins, the neural isoform of nitric oxide synthases, which is selectively expressed in macula densa cells, is critical in the tubuloglomerular feedback and renin signaling cascade.
What happens to sodium in the macular densa?
When there is a decrease in the sodium concentration, less sodium is reabsorbed in the macular densa cells. The cells increase the production of nitric oxide and Prostaglandins to vasodilate the afferent arterioles and increase renin.
