juxtaglomerular cell

{{Short description|Cell in kidneys that produces & secretes renin}}

{{Distinguish|granule cell}}

{{More references|date=November 2022}}

{{Infobox anatomy

| Name = Juxtaglomerular cell

| Image = Juxtaglomerular cells.JPG

| Caption = Microscopic image of juxtaglomerular cells

| Image2 = Renal corpuscle-en.svg

| Caption2 = Drawing of renal corpuscle showing juxtaglomerular cells (as granular cells, in green), macula densa cells and extraglomerular mesangium.

}}

Juxtaglomerular cells (JG cells), also known as juxtaglomerular granular cells are cells in the kidney that synthesize, store, and secrete the enzyme renin.{{cite web |last1=Kopp |first1=Ulla C. |title=Neural Control of Renin Secretion Rate |url=https://www.ncbi.nlm.nih.gov/books/NBK57240/ |publisher=Morgan & Claypool Life Sciences |access-date=18 November 2022 |language=en |date=2011}} They are specialized smooth muscle cells mainly in the walls of the afferent arterioles (and some in the efferent arterioles){{Need sources|date=May 2023|reason=(Granular cells (or juxtaglomerular cells) are modified smooth muscle cells of the afferent arteriole located near its entrance into the renal corpuscle) we know it is there in the afferent arteriole}} that deliver blood to the glomerulus. They are located near the glomerulus, hence the name. In synthesizing renin, they play a critical role in the renin–angiotensin system and thus in autoregulation of the kidney.

Juxtaglomerular cells secrete renin in response to a drop in pressure detected by stretch receptors in the vascular walls, or when stimulated by macula densa cells. Macula densa cells are located in the distal convoluted tubule, and stimulate juxtaglomerular cells to release renin when they detect a drop in chloride concentration in tubular fluid. Together, juxtaglomerular cells, extraglomerular mesangial cells and macula densa cells comprise the juxtaglomerular apparatus.

In appropriately stained tissue sections, juxtaglomerular cells are distinguished by their granulated cytoplasm.

Similar to cardiac tissue, juxtaglomerular cells harbor β1 adrenergic receptors. When stimulated by epinephrine or norepinephrine, these receptors induce the secretion of renin. These cells also respond directly to a decrease in systemic blood pressure which is manifested as a lower renal perfusion pressure.