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what does the RAAS regulate?
fluid & electrolyte balance
what converts Angiotensin I to angiotensin II?
angiotensin converting enzyme
effects of angiotensin II
stimulation of aldosterone release
--> raise BP
can act on heart /blood vessels to cause hypertrophy/remodeling (redistribution of mass)
direct and indirect ways of causing vasoconstriction by angiotensin II
Direct: effects arterioles more than veins -> raises BP
Indirect: release of E/NE, acts on CNS to increase sympathetic stimulation of blood vessles
action of aldosterone
- works on DCT of kidney
- retain sodium -> retains water
- -> raises blood volume/pressure
what two mechanisms promote renal retention of water?
constriction of renal vessels -> less GFR
release of aldosterone
what can stimulate RAAS?
- blood loss
- sodium depletion
What does renin do?
- catalyzes formation of angiotensin I from angiotensinogen
- produced in kidneys
What do ACE inhibitors treat? how?
- hypertension, heart failure, diabetic nephropathy, myocardial infarction
- suppress formation of angiotensin II
- -> dilate blood vessels
- -> reduce blood volume
- -> prevent/reverse pathologic changes in heart/vessels
- also produce bradykinin, promotes vasodilation
are all ACE inhibitors the same?
produce similar effects, but no single ACE inhibitor is approved to treat all conditions
how do ACE inhibitors help heart failure?
lower arterial tone -> improve regional blood flow
reduce cardiac afterload -> increase cardiac output
venous dilation -> reduce pulmonary congestion/peripheral edema
dilate blood vessels in kidneys -> increase renal blood flow -> promote excretion of sodium and water
less blood volume -> less strain on heart
adverse effects of ACE inhibitors
hypotension (after first dose)