Question

Which of the following would result in reduced blood volume and blood pressure?

Dehydration

Consumption of hard alcohol (a diuretic)

Increased renin secretion by the granular cells

Natriuresis as caused by elevated atrial natriuretic peptide levels

Insertion of ENaC molecules into the apical side of the P cells

Inhibition of angiotensin converting enzyme

Increased angiotensinogen production but with no change in available renin.

In the absence of ACE inhibition, increased ANG I production

Answer 1

Dehydration may occurs due to severe vomiting or diarrhoea. Dehydration results in excess removal of water and other ions mainly sodium. The outflow of water and other substances exceeds the input in dehydration. This causes depletion of blood volume and the blood pressure drops.
Hard alcohol is a diuretic which means it increases the urine output. This results excess loss of water and pther ions in the urine which results in loss of water. Blood volume and blood pressure reduces.
Renin induces the release of angiotensinogen from the liver. This angiotensinogen is converted into angiotensin l and angiotensin ll by angiotensinogen converting enzyme. Angiotensin causes vasoconstriction. It also acts on pituitary and adrenal gland to release ADH and aldosterone which increases sodium and water reabsorption and results in increased blood volume and blood pressure.
Increased atrial natriuretic peptide acts on kidney to decrease renin secretion. This inhibits release of angiotensinogen and aldosterone. It also inhibits release of ADH and suppresses thirst. It acts on blood vessels to vasodilate. ANP also decreases the sympathetic activity. The effect of increased ANP is decreased blood volume and blood pressure.
ENaC are selectively permeable to sodium and increases sodium reabsorption from kidney. So Insertion of ENaC molecules into the apical side of the P cells will result in increased sodium and water retention. This increases blood pressure and volume.
ACE is responsible for converting angiotensinogen to active forms angiotensin l and ll that stimulates release of ADH and aldosterone and increases sodium and water retention. Thereby increasing the blood pressure and volume. Inhibition of ACE results in decreased blood volume and blood pressure.
Renin is needed to convert angiotensinogen into angiotensin l which is later converted into angiotensin ll by the action of ACE. If renin is not present angiotensinogen will not be converted into its active form angiotensin ll and exert its effect to increase volume and pressure of blood.This will not affect the blood volume and blood pressure.

Increased angiotensinogen l production will increase its conversion to angiotensin ll by the action of ACE. This will increase sodium and water retention and increase blood pressure and volume.
ANSWER : dehydration, consumption of hard alcohol, inhibition of ACE, Natriuresis as caused by elevated atrial natriuretic peptide levels.