Vasoactive Peptides & Inhibitors Flashcards
- where is angiotensinogen synthesized?
- what does it become and due to what enzymes?
- how is its synthesis regulated?
- synthesized in the liver
- converted by renin to angiotensin I
- renin released by juxtaglomerlar cells on afferent arteriole in response to
- NE/EPI release during hypovolemic state (low BP, low NaCl)
- renin released by juxtaglomerlar cells on afferent arteriole in response to
- angiotensin I converted to angiotensin II
- angiotensin II inhibits renin release
- antiogensin II –> III –> IV

antiotensin II receptors
- where are they found?
- what does stimulation by angiotensin cause?
- AT1 receptors
- found in the vascular smooth muscle
- stimulates PLC in membrane
- PLC stimulation results in IP3 release (from PIP2)
- IP3 release causes Ca++ release –> smooth muscle contraction
- –> vasoconstriction
- AT2 receptors
- found in fetal tissues
- angiotensin II binding maintains healthy tissues
- possibly found on endothelium and involved in NO mediated vasodilation

effects of AT1- angtiotensin II binding
- SNS outflow: release of catecholamines from nerve terminals
- cardiac:
- hypertrophy of cardiac and vascular muscle
- vasoconstriction
- CNS:
- perception of thirst to promote fluid intake
- ADH release
- ADH released from hypothalamus
- ADH increases water reabsorption
- ADH released from hypothalamus
- kidney: aldosterone release
- rentention of Na+ and fluid

pathological effects of angiotensin II
- hypertension (by vasoconstriction/increasing blood volume)
- heart failure (hypertension increases afterload against which the heart may word)
- cardiac remodeling after MI (causes hypertrophy)
- chronic renal diseases (efferent arterioles constriction increases glomerular hydrostatic pressure, injuring glomerulus)
list the classes of drugs that inhibit angiotensin II’s pathological effects
= inhibition of RAAS system
- renin inhibitors: inhibit conversion of antiotensinogen to angiotensin I
- ACE inhibitors: inhibit conversion of angiotensin I to angiotensin II
- AT receptor blockers

what three factors can increases renin release?
- drop in tubular NaCl
- low blood pressure
- stimulation of B1 receptors
aliskiren
- what kind of RAAS inhibitor
- MOA
- renin inhibitor: inhibits renin function
- MOA binds to renin and inhibits its function
- this inhibits the conversion of angiotensin to angiotensin I
- this subsequently decreases production of angiotensin II
- decrease in angiotensin II releases the negative feedback inhibition that it typically has over renin
- ends up causing renin secretion to actally i_ncrease_
- decrease in angiotensin II releases the negative feedback inhibition that it typically has over renin

ACE inhibitors MOA
ACE inhibitors
- inhibit conversion of angiotensin I to angiotensin II
- inhibit breakdown of bradykinin to inactive form, thus increasing concentration of bradykinin (a vasodilator)
* this contributes to anti-hypertensive effects mediated by antiogensin II decrease

AEs seen in ACE inhibitors but not ARBs
can cause a persistent dry cough - this is due increase in bradykinin
AT1 antagonists
- MOA
- indication
- MOA: bind AT1 receptors (found on smooth muscle vasculature) and inhibit binding of angiotensin
- indications: used in hypertensive patients who cannot tolerate the persistent dry cough caused by ACE inhibitors
- this is because they do NOT cause in increase in bradykinin like ACE inhibitors

effects of RAAS inhibition on cardiovascular system:
- decrease sympathetic nervous system
- decrease cardiovascular remodeling by
- inhibiting cardiovascular hypertrophy, and
- lowering work on the heart (pre-load and afterload), by
- inhibiting vasoconstriction
- reduceing blood volume
- by inhibiting ADH and aldosterone

renal effects of RAAS inhibition
-
reduce proteinurea
- proteinurea = presence of proteins in the urine due to damage of the glomerular capillaries
- constant increased glomerular pressure promotes filtration of otherwise not filtered proteins –> protein in the urine –> proteinurea
- RAAS inhibition:
- leads to vasodilation of the efferent arteriole, thus preventing high glomerular pressure
- proteinurea = presence of proteins in the urine due to damage of the glomerular capillaries
-
reduce risks of type 2 diabetes
- increase insulin sensitivity?
list the increases in RAAS products that will be seen as a result of renin inhibition, ACE inhibitors, and AT1 blocker
- Renin enzyme inhibitor: increase renin release
- ACE inhibitors: increase renin, Ang I
- AT1 blockers: increase renin, Ang I and II

what are the ACE inhibitors?
“prils”
captopril, lisonopril
what are the AT1 Receptor blockers (ARBs)?
“sartans”
losartan, valsartan
what renin enzyme inhibitor did we discuss?
aliskiren
uses of ACE inhibitors
- hypertension
- heart failure
- acute MI
- chronic renal disease: slows the rate of decline in renal function
- reducing intra-glomular pressure
- increasing selectivity of glomerular filtering membrane
diabetic kidney disease
- discuss the pathology
- why are ACE inhibitors an effetive treatment?
- diabetic kidney disease is characterized by mesangial expansion and glomerular basement thickening
- this causes contraction of the arterioles
- leads to a decrease in surface area of the basement membrane
- decreased surface area –> decreased GRF
- ACE inhibitors:
- dilate renal arterioles
- decrease glomelular capillary pressure
- decreased glomerular injury –> surface area restored –> restored GFR
- decrease glomelular capillary pressure
- increase selecitivty of filtering membrane
- such that growth factors are not leaking out into filtrate, damaging mesangium
- dilate renal arterioles
clinical uses of AT1 receptor antagonists (ARBs)
same as ACE inhibitors- hypertension, heart failure, chronic kidney disease, acute mi
indicated especially in someone intolerant to persistent dry cough
use of aliskiren
(renin enzyme inhibitor)
use = hypertension (not the first line though)
AEs of RAS inhibitors
ACE inhibitors, ARBs and renin inhibitor:
- hypotension
- headache, dizziness
- GI disturbances
-
renal function impairment
- ang II inhibition will vasodilate efferent arteriole, lowering glomular hydrastatic pressure. though this protects the glomerulus, it does decrease GFR. somebody with impaired renal function already has a low GFR, and adding an ACE inhibitor/ARB could be dangerous
-
hyperkalmia
- Ang II production stimulates aldsosterone secretion. aldstonerone stimulates Na/K exchanger that reabsorbs Na+ in exchanger for K+ secretion. inhibition of Ang II and thus aldosterone will slow K+ secretion thus causig K+ retention
ACE inhibitors specifically: cause the following AEs as a result of increasing bradykinin levels
- persistent dry cough
- angioedema
drug drug interactions of RAS inhibitors:
- NSAIDS longer than five days:
- they counteract the anti-hypertenive effects of RAS inhibitors
- trimethoprim other K+ sparing diuretics
- these drugs increase serum potassium
- hyperkalemic effects of RAS inhibitors coud be dangers
- litium - can cause lithium toxicity
mechanism by which co-administration of trimethoprim and RAS inhibitors can cause hyperkalmia
- in the principle cells of collecting tubules
- Na+ reabsorption leaves a negative intraluminal charge
- this draws K+ into the the filtrate
- trimethoprim behaves like a K+ sparing diuretic. in combination with RAS inhibitors, which inhibit aldosterone thus inhibiting K+ secretion, this can lead to hyperkalemia

contraindications of RAS inhibitors
- pregnancy
- pts with bilateral renal artery stenosis:
- these patients are hypoperfused
- RAS inhibitors will lower GRF further impairing renal function








