Question

. List the functions of the hormones/enzyme listed below:

• Aldosterone

• Renin

• Antidiuretic Hormone (ADH)

Answer 1

Function of Aldosterone:

1.

The Aldosterone hormone is a hormone produced by the adrenal gland. The hormone acts mainly in the functional unit of the kidneys to aid in the conservation of sodium, secretion of potassium, water retention and to stabilize blood pressure. Overall, the hormone helps to increase the reabsorption of water and ions in the kidneys to maintain sufficient blood volume levels, stabilizing the blood pressure

2.Aldosterone affects sodium, potassium, total fluid in the body, and blood pressure.

3.Aldosterone causes the kidneys to hold onto more sodium, which leads to more water staying in the body. The more fluid the body holds onto, the higher the blood pressure may become. Potassium may decrease as the amount of aldosterone increases. Aldosterone also directly affects the heart and blood vessels.

So in a nutshell,

● Aldosterone regulate osmolality in the body.

● It acts on the DCT and the collecting duct and increases the reabsorption of Na*

During hypersecretion of aldosterone, the loss of sodium through urine is only few milligram per day.

But during hyposecretion of aldosterone, the loss of sodium through urine increases (hypernatriuria) up to about 20 g/day.

● Aldosterone is a mineralocorticoid hormone produced by aldosterone synthase (CYP11B2) in the zona glomerulosa of the adrenal cortex. Aldosterone binds to mineralocorticoid receptors (MR; NR3C2) and MR-aldosterone complexes regulate the expression of genes involved in the retention of sodium, the secretion of potassium, and water reabsorption, all of which may result increased blood pressure.

● Aldosterone also increases sodium reabsorption in sweat glands.

Function of Renin:

1.Only known function of Renin is Cleavage of angiotensinogen to angiotensin I

[renin cleaves angiotensinogen (produce by liver) to Ag 1

AT1 cleaves to become AT2

AT2 cleaved to become AT3

AT3, which is less potent, act on adrenal cortex and increase aldosterone production]

2.Cells in the kidneys respond to low blood pressure by releasing an enzyme called renin. Renin causes the kidneys to reabsorb sodium. Sodium reabsorption, in turn, is always accompanied by water retention. This helps to restore blood volume and blood pressure.

So it Controls fluid volume and blood pressure

The renin angiotensin system (RAS) plays a central role in the brain to regulate blood pressure (BP

[- low BP reduces oxygen perfusion - CNS particularly susceptible

In the result it causes lack of concentration, dizziness, nausea, fainting.

In such situations, RAS responds to increase BP over long and short terms.]

3.Renin is a neutral serine protease that clips a decapeptide ANGIOTENSIN I from angiotensinogen(circulating a2-glodulin)

Functions of ADH:

● Effects on the Kidney

1. Antidiuresis or decreased formation of urine, and the hormone was named for this effect. Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. In the absense of antidiuretic hormone, the collecting ducts are virtually impermiable to water, and it flows out as urine.

2. Antidiuretic hormone stimulates water reabsorbtion by stimulating insertion of "water channels" or aquaporins into the membranes of kidney tubules. These channels transport solute-free water through tubular cells and back into blood, leading to a decrease in plasma osmolarity and an increase osmolarity of urine.

● Effects on the Vascular System

In many species, high concentrations of antidiuretic hormone cause widespread constriction of arterioles, which leads to increased arterial pressure. It was for this effect that the name vasopressin was coined. In healthy humans, antidiuretic hormone has minimal pressure effects.

● Effects on Central nervous system

Vasopressin released from centrally projecting hypothalamic neurons is involved in aggression, blood pressure regulation, and temperature regulation.