Aldosterone Flashcards
where is aldosterone produced?
Zone Glomerulus
Where is the site of action of Aldosterone
Distal tubule and collecting ducts of kidney
What are the effects of aldosterone?
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
describe the aldosterone cellular mechanism of action
- binds to specific intracellular mineralocorticoid receptor within target cells
- Receptor-ligan complex
- transcription of genes
- synthesis of proteins
- Promotes sodium transport by target cells of the kidney
- response to administration about 1 hour
What are aldosterone responsive cells protected by?
11 beta-hydroxysteroid dehydrogenase (converts cortisol to cortisone)
The renin angiotensin system
Renin-proteolytic enzyme produced in the juxtaglomerular region of the nephrons of the kidney
Where are renin secreting cells located?
surround the afferent arteriole just before it enters the malpigian corpuscle and branches into the glomeruli capillaries
Where does Renin cleave angiotensin?
between Val-Leu (derived from alpha 2 globulin-liver)
What does Renin produce?
a decapeptide -> ANGIOTENSIN 1 (biologically inactive)
Angiotensin 1 is converted into angiotensin 2 where and how?
By cleavage of an octopeptide primarily in the lungs, by angiotensin converting enzyme (ACE) (Biologically active)
what does angiotensin 2 do?
stimulates zona glomerulosa to produce and secrete aldosterone
Describe how angiotensin 2 works:
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).
The production of angiotensin is the ____ _____ _____
Rate-limiting step
What are the other factors involved in aldosterone release?
ACTH
alpha MSH
What inhibits aldosterone release?
somatostatin and ANP
What effect does high potassium have on aldosterone secretion?
directly increase aldosterone secretion, thus increasing excretion of potassium
What is the dysfunction: MINERALOCORTICOID EXCESS usually due to?
adrenal tumour that produces aldosterone
excessive renin secreto
Excess ACTH cause hyper secretion of mineralocorticoid by stimulating steroidogenesis in Zona Glomerulus
What are the symptoms of mineralocorticoid excess?
- Retention of sodium which leads to hypertension
- Raised blood pressure
- Blurring of vision
- Cerebral vascular damage
What is the treatment of mineralocorticoid excess?
Surgical removal of the tumour
Addison’s disease is?
lack of adrenal hormones
What might addison disease be caused by?
autoimmune process
inflammatory disease
haemorrhage
removal of adrenal glands
Symptoms of addison disease:
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
Treatment of Addisons Disease:
administration of mineralocorticoids such as 9alpha-fluorocortisol
Administration of hydrocortisone to replace cortisol
