Granular cell

Juxtaglomerular cells (JG cells), also known as juxtaglomerular granular cells are cells in the kidney that synthesize, store, and secrete the enzyme renin. They are specialized smooth muscle cells in the tunica media of the walls of the afferent arterioles and – to a lesser extent – efferent arterioles of 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.