Question

Angiotensinogen is a protein produced and secreted by
A. Macula densa cells
B. Endothelial cells
C. Liver cells
D. Juxtaglomerular

Answer 1

Hint:Angiotensinogen is a $\alpha -2-$globulin. It has many other roles that are not related to angiotensin formation. It is also called serpin A8 as it belongs to the serpin protein family. It is produced by the hepatocyte cells.

Complete answer:Angiotensinogen is the key precursor for the production of angiotensin. It is also a rennin substrate. The N-terminus of angiotensinogen is cleaved by rennin to make angiotensin I. The angiotensin I, is later modified into angiotensin II. The secretion of plasma angiotensin is controlled by plasma corticosteroids, thyroid hormone, estrogen, and angiotensin II levels.
The angiotensinogen has many other roles than just the production of angiotensin. Hypertension is linked with increased levels of angiotensinogen.
Angiotensinogen is secreted by the hepatocyte cells of the liver cells. it is found in the $\alpha -$ globulin fraction of blood plasma. It belongs to the serpin family of proteins called the serine-protease inhibitor proteins. But angiotensinogen itself has no role in protease inhibition. Angiotensinogen is also expressed at high levels in the brain.
Hence the correct answer is option C) Liver cells

Note: Angiotensin I is converted into angiotensin II by the action of the Angiotensin-converting enzyme or ACE. It is present in the lungs majorly but also in endothelial cells, brain cells, and kidney epithelial cells. Angiotensin II increases blood pressure and thus in increased levels, the ACE inhibitor molecules are used to inactivate ACE complexes. Remember that ACE is also the key recognition site for coronavirus.