Angiotensinogen is a protein produced and secreted by A. Macula densa cellsB. Endothelial cellsC. Liver cellsD. Juxtaglomerular

C. Liver cells

Angiotensinogen is indeed a protein produced and secreted by liver cells. It is a precursor molecule that plays a crucial role in the renin-angiotensin system, a hormonal system involved in regulating blood pressure and fluid balance in the body.

The production of angiotensinogen occurs primarily in the liver, where it is synthesized and released into the bloodstream. Once released, angiotensinogen circulates in the blood until it encounters the enzyme renin, which is primarily produced and secreted by juxtaglomerular cells in the kidneys. Renin acts on angiotensinogen, cleaving it to produce angiotensin I, which is further converted into angiotensin II by the action of the angiotensin-converting enzyme (ACE) mainly found in endothelial cells.

Angiotensin II is a potent vasoconstrictor and also stimulates the release of aldosterone, a hormone that regulates sodium and water balance. These actions of angiotensin II help increase blood pressure and maintain fluid balance in the body.