Question

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

Answer 1

Hint:Angiotensinogen is a component of the RAS (renin angiotensin system) which regulates blood pressure and balance fluid in the body. Juxtaglomerular cells secrete renin that acts upon angiotensinogen to release angiotensin I and by angiotensin-converting enzyme it is converted to angiotensin II.

Complete answer:
>Angiotensinogen is found in alpha globulin in plasma and in tissues expressing RAASs. It is a peptide hormone which helps in vasoconstriction and increase in blood pressure.
>Angiotensinogen is a renin substrate and also a non-inhibitory member of the serpin family of proteinase inhibitors.
Physiology of angiotensinogen:
>It is a 485 amino acid protein and is a precursor molecule for angiotensin II.
>The molecular weight of circulating protein may vary.
>The synthesis of angiotensinogen is stimulated by thyroid hormones, estrogens, glucocorticoids, angiotensin II.
>It is produced in various tissues like adipose tissue, kidney, heart and brain.
>The levels of angiotensinogen are determined by the rate of production by hepatocytes (liver cells).
>Angiotensinogen protein is also produced by Adipocytes.

Additional information:The sex determining region of Y- chromosome also responsible for the production of this protein in humans as well as in rodents. Estrogen and testosterone are also responsible to regulate the level of angiotensinogen.

The correct answer is liver cells.

Note:The macula densa cells are found in Kidney and control kidney functions including renal blood flow, glomerular filtration. Endothelial cells line blood vessels and help in regulation of exchange between surrounding tissues and blood.