Question

Angiotensin is a protein produced and secreted by?

Answer 1

Angiotensin is a peptide hormone. Angiotensin is a part of the RAAS -Renin-Angiotensin System which plays a crucial role in regulating Blood pressure. Angiotensin stimulates the release of aldosterone from the cortex of the adrenal gland.

Complete answer:
The liver synthesizes and releases angiotensinogen. It is the inactive form of angiotensin which is later on activated when the RAAS is triggered.
When the blood pressure decreases, it activates RAAS. The decrease in blood pressure leads to the release of renin. Renin converts angiotensinogen to angiotensin I. Here comes the role of ACE - Angiotensin-converting enzyme. It converts angiotensin I into angiotensin II. Angiotensin II acts on receptors in the brain, kidney, vessel wall, and heart. By acting on the vessel walls, causes vasoconstriction leading to an increase in blood pressure thus correcting it. Angiotensin II also acts on the pituitary leading to the release of vasopressin (ADH- Antidiuretic hormone). ADH functions by increasing the absorption of sodium and water from the renal tubules.
It also causes the release of aldosterone from the adrenal gland. Aldosterone leads to the increased absorption of sodium and water from the renal tubules. This increases the blood volume finally ending in a rise in blood pressure. When the blood pressure reverses to normal, RAAS is deactivated.

Note: ANF (Antinatriuretic peptide) counteracts the effect of RAAS by decreasing the blood pressure. The angiotensin corrects the heart rate without affecting the function of the heart. The angiotensin antagonists are used to control blood pressure in patients of HTN.