Aldosterone

Question 1

where is aldosterone produced?

Answer 1

Zone Glomerulus

Question 2

Where is the site of action of Aldosterone

Answer 2

Distal tubule and collecting ducts of kidney

Question 3

What are the effects of aldosterone?

Answer 3

increases sodium re-absorption and increases the excretion of potassium and hydrogen ions.

• Raises blood pressure
• increases plasma volume
• increases the sensitivity of arteriolar muscle to vasoconstriction agents

Question 4

describe the aldosterone cellular mechanism of action

Answer 4

1. binds to specific intracellular mineralocorticoid receptor within target cells
2. Receptor-ligan complex
3. transcription of genes
4. synthesis of proteins
5. Promotes sodium transport by target cells of the kidney
6. response to administration about 1 hour

Question 5

What are aldosterone responsive cells protected by?

Answer 5

11 beta-hydroxysteroid dehydrogenase (converts cortisol to cortisone)

Question 6

The renin angiotensin system

Answer 6

Renin-proteolytic enzyme produced in the juxtaglomerular region of the nephrons of the kidney

Question 7

Where are renin secreting cells located?

Answer 7

surround the afferent arteriole just before it enters the malpigian corpuscle and branches into the glomeruli capillaries

Question 8

Where does Renin cleave angiotensin?

Answer 8

between Val-Leu (derived from alpha 2 globulin-liver)

Question 9

What does Renin produce?

Answer 9

a decapeptide -> ANGIOTENSIN 1 (biologically inactive)

Question 10

Angiotensin 1 is converted into angiotensin 2 where and how?

Answer 10

By cleavage of an octopeptide primarily in the lungs, by angiotensin converting enzyme (ACE) (Biologically active)

Question 11

what does angiotensin 2 do?

Answer 11

stimulates zona glomerulosa to produce and secrete aldosterone

Question 12

Describe how angiotensin 2 works:

Answer 12

Sodium depletion - angiotensin II has a potent effect on the renal circulation: decrease rate of glomerular filtrate and therefore decrease renal secretion of sodium.

(Angiotensin II also directly affects arterioles and thus can regulate BP directly as well as indirectly).

Question 13

The production of angiotensin is the ____ _____ _____

Answer 13

Rate-limiting step

Question 14

What are the other factors involved in aldosterone release?

Answer 14

ACTH

alpha MSH

Question 15

What inhibits aldosterone release?

Answer 15

somatostatin and ANP

Question 16

What effect does high potassium have on aldosterone secretion?

Answer 16

directly increase aldosterone secretion, thus increasing excretion of potassium

Question 17

What is the dysfunction: MINERALOCORTICOID EXCESS usually due to?

Answer 17

adrenal tumour that produces aldosterone
excessive renin secreto
Excess ACTH cause hyper secretion of mineralocorticoid by stimulating steroidogenesis in Zona Glomerulus

Question 18

What are the symptoms of mineralocorticoid excess?

Answer 18

1. Retention of sodium which leads to hypertension
2. Raised blood pressure
3. Blurring of vision
4. Cerebral vascular damage

Question 19

What is the treatment of mineralocorticoid excess?

Answer 19

Surgical removal of the tumour

Question 20

Addison’s disease is?

Answer 20

lack of adrenal hormones

Question 21

What might addison disease be caused by?

Answer 21

autoimmune process
inflammatory disease
haemorrhage
removal of adrenal glands

Question 22

Symptoms of addison disease:

Answer 22

tiredness & weakness
Anorexia and vomitting
loss of sodium reabsorption in the distal tubule of the kidney, low sodium and high potassium
Hypotension and collapse
High levels of ACTH are secreted to compensate. other POMC peptides co-secreted - causes hyper pigmentation of skin

Question 23

Treatment of Addisons Disease:

Answer 23

administration of mineralocorticoids such as 9alpha-fluorocortisol
Administration of hydrocortisone to replace cortisol