Which cells in the kidney secrete renin?

Juxtaglomerular cells are specialized smooth muscle cells located in the walls of the afferent arterioles that supply blood to the glomeruli in the kidneys. These cells play a crucial role in regulating blood pressure and fluid balance by secreting renin, an enzyme that initiates a cascade of events leading to the production of angiotensin II, a potent vasoconstrictor. Renin release is triggered by various factors, including low blood pressure, low sodium concentration detected by the macula densa cells, and sympathetic nervous system stimulation.

The unique role of juxtaglomerular cells in the renal system emphasizes their importance in the regulation of the body's blood pressure and volume. In contrast, while macula densa cells are involved in the detection of sodium levels and can influence the activity of juxtaglomerular cells, they do not secrete renin themselves. Podocytes are specialized cells that form a part of the glomerular filtration barrier, and proximal tubule cells are primarily responsible for reabsorbing nutrients and water from the filtrate, neither of which are directly involved in the secretion of renin. Therefore, the juxtaglomerular cells are correctly identified as the cells responsible for renin secretion