Renin is secreted by:

The JG apparatus consists of 3 structures: (1) The granular juxtaglomerular cells in the afferent aeriole, (2) The macula densa at the end of the thick ascending limb and the initial poion of DCT, (3) The extraglomerular mesangial cells. Granular cells of the afferent aeriole contain smooth muscle myofilaments and they manufacture, store, and release renin. Cells in the macula densa are the epithelial cells in the thick ascending limb of the loop of Henle (end poion) and the initial pa of DCT. They are involved in tubuloglomerular feedback, which influences the RBF and GFR Extraglomerular mesangial cells are continuous with mesangial cells of the glomerulus; they may transmit information from macula densa cells and the granular JG cells. Coical interstitial cells of kidneys secrete the hormone Erythropoietin in response to a fall in the local tissue PO2. It stimulates erythropoiesis.