Aldosterone Flashcards
Adrenal cortex is organized into 3 distinct zones
- zona glomerulosa
- Zona fasciculata
- zona reticularis
Importance of Aldosterone
essential to sodium retention
in 3 primary tissues: principal cells (kidney, large intestine, sweat glands)
2 types of salt retention by the kidney
regulated + non-regulated (countercurrent system»_space; osmotic gradient)
major site of mineralocorticoid activity
Kidney
What happens when aldosterone binds to the mineralocorticoid receptor (MR) in target cell?
affects transcriptional changes (typical of steroid hormone action)
What retains Na+ and H2O in the body
aldosterone stimulates Na+ reabsorption in the collecting ducts
what does Aldosterone cause in the kidney
increase blood pressure by increasing extracellular fluid volume
increase urine excretion of K+ and H+
main function of aldosterone is to
sustain extracellular fluid volume by conserving body sodium
when body sodium is depleted
the fall in extracellular fluid and plasma volume decreases renal arterial blood flow and pressure (activating RAA system)
Aldosterone is largely secreted in response to
signals that arise from the kidney when a reduction in circulating fluid volume is sensed
Aldosterone facilitates ….
clearance of potassium from the extracellular fluid
potassium stimulates
aldosterone synthesis
- providing feedback control mechanism to control potassium levels
potassium depletion
reduced aldosterone secretion
stimulation of aldosterone synthesis by potassium
depolarization of zona glomerulosa cell membrane
- causing Ca+2 voltage changes to increase in intracellular Ca 2+ stimulates expression of P450aldo
regulation of aldosterone
+
Potassium (main)
Angiotensin 2 (main)
ACTH (not so much)
-
ANP (atrial natriuretic peptide
RAA
Renin- Angiotensin - Aldosterone system
Granular juxtaglomerular cells are going to feel
Blood pressure
Macula Densa sense
Sodium levels
What stimulates the release of renin
Low blood pressure and low sodium levels
Renin is produced in
juxtaglomerular cells
Enzyme made by the liver
angiotensinogen
What makes Angiotensin 1
conversion btw Angiotensinogen and renin
What makes Angiotensin 2
Angiotensin 1 with ACE (angiotensin converting enzyme)
Angiotensin 2 is potent in controlling
- increasing blood pressure
- stimulating NEP by neurons $ adrenal medulla
- reabsorption of K+
- also helps also aldosterone secretion
- AVP to help with H2O absorption
- water absorption
angiotensin 3
potent pressor hormone controls aldosterone
how to get angiotensin 2 to 3
amino peptidase A
Angiotensin 2 &3 effects
increase
- aldosterone synthesis and secretion
- vasoconstriction
- release of AVP
- release of adrenal catecholamines
- central sympathetic outflow
Angiotensin 2 goal
maintain normal extracellular volume and blood
increasing transcription of P450aldo
increases aldosterone production
increasing vasoconstriction
increase blood pressure and renal blood flow (decrease renin)
Release EPI and NEP from
adrenal medulla
angiotensin 2 enhance activity of the
sympathetic nervous system and NE release in nerve terminals
promote release of AVP
increase water reabsorption in collecting ducts
Angiotensin 2 receptors
AT1 & AT2
AT1
- adrenal, cardiovascular, renal effects
- Gq»_space; Ca+2 to elicit response
AT2
associated with effects NOT related with aldosterone
Regulation of aldosterone
(if you have tooo much)
Atrial natriuretic Peptide (ANP)
as a result of volume expansion , atrial myocytes secrete
ANP»_space; binds to receptors in the zona G. to inhibit aldosterone synthesis
ANP counterbalance the effect of
RAA on aldosterone secretion
- ANP acts by increasing cGMP (opposes cAMP & inhibits aldosterone)
- ANP also reduces aldosterone indirectly by inhibiting renin release
