Renin-Aldosterone-Angiotensin System Flashcards
Overview
What cells secrete renin?
Juxtoglomerular cells
What factors lead to renin release?
Low NaCl in DCT
Low afferent arteriole pressure
B1 adrenergic stimulation
What acts as the sensor for NaCl in the DCT?
Macula densa
What chemical leads to the release of renin?
Prostaglandins
What happens if the macula densa senses high levels of NaCl?
It inhibits NO and makes adenosine
What happens if BP is low?
Low baroreceptor activation (afferent arterioles)
No NO inhibition and adenosine levels fall and afferent arterioles open
PG release from macula densa
Renin released from JGA
Angiotensin and Aldosterone release and an increase in NA retention and BP rises
What happens if BP is high?
Increased baroreptor activation (afferent arterioles) and the myogenic response kicks in
Afferent arteriole constrictrs due to NO inhibition and adenosine release (blocks renin)
GFR lowers and kidneys get protected
What happens if GFR is high?
Myogenic response via high NaCl in macula densa.
Adenosine released and NO inhibited to close afferent arteriles
What does NO do?
Vasodilates afferent arteriole to increase GFR
What does adenosine do?
Restricts afferent arteriole to lower GFR
What does renin do?
Changes Angiotensinogen to Angiotensin 1
This is converted to Angiotensin 2 by ACE
What does Angiotensin 2 do?
- Causes aldosterone release from adrenal cortex
- Constricts efferent arterioles to increase GFR pressure
What does aldosterone do?
Increase Na retention and K excretion and therefore increased water retention
How do ace inhibitors affect the system?
Stop Angiotensin 2 being produced and also dilate efferent arterioles so lower GFR
DO NOT USE IN SHOCK OR VOLUME DEPELETED STATES
What do NSAIDS do to the system?
Constrict afferent arterioles and lower GFR
Stop vasodilatory prostoglandins
What does spiranolactone do?
Inhibits aldosterone
What are some high renin states?
Renal artery stenosis
Volume depletion (to increase renal perfusion pressure)
Low cardiac output
What happens in unilateral renal stenosis?
Refractory HTN as renin levels increased (this is do increase GFR via efferent arteriole constriction)
No decline in kidney function as one one affected
What happens in bilateral renal stenosis?
Refractory HTN and decline in renal function
Dont give ACEI has dilates efferent so futher reduces GFR
Where are the baroreceptors for kidney perfusion?
Afferent arterioles
