The juxtaglomerular cells (JG cells, or granular cells) are cells in the kidney that synthesize, store, and secrete the enzyme renin.

Also, adenosine inhibits renin release in JG cells via A2 receptors on JG cells using a Gi pathway.

Decreased Cl- flow stimulates tubuloglomerular autoregulation, a signal (thought to be regulated by adenosine) sent to the nearby juxtaglomerular cells of the afferent arteriole, causing the JG cells to release the protease renin into circulation.

Renin is secreted from granules in the JG cells, and once in the blood stream, it acts as a protease to convert angiotensinogen to angiotensin I, which is converted by angiotensin converting enzyme, to angiotensin II, which, in turn, stimulates aldosterone release.