Unit 6 - cardiovascular system 4 Flashcards
What is the function of angiotensin-converting enzyme?
Catalyses the conversion of angiotensin I to potent active vasoconstrictor angiotensin II
Where are ACE enzymes found?
On the luminal surface of capillary endothelial cells, predominantly in the lungs
Which receptor is the target of angiotensin II?
AT1
AT2
What does the AT1 receptor mediate?
Classic angiotensin II actions
- vasoconstriction
- aldosterone stimulation
- renal Na+ and fluid retention
- ADH (vasopressin) release from posterior pituitary
- cardiac and vascular muscle cell growth
- stimulation of thirst centres in the brain
What was the first ACE inhibitor synthesised in 1975?
Captopril
What are the effects of ACE inhibitors?
Decreased angiotensin II production - vasodilation - reduction in aldosterone secretion - reduction in ADH secretion - reduced cardiac and vascular hypertrophy - decrease in Na+ and water retention - decrease in blood volume Inhibit bradykinin degredation - vasodilation via - NOS/NO - COX/PGI2
What is an ARB?
Angiotensin II receptor blocker
Which receptors are important in relation to cardiovascular regulation?
AT1 receptors
What are the advantages of angiotensin II receptor blockers (ARB’s)?
Aren’t associated with dry cough
What are the disadvantages of angiotensin II receptor blockers?
No effect on bradykinin
- less effective in low-renin hypertensives
Why are angiotensin II receptor blockers (ARBs) more effective at preventing angiotensin II mediated vasoconstriction?
They directly target AT1 receptors
Give some examples of angiotensin II receptor blockers?
- losartan
- candesartan cilexetil
What is the function of a Ca2+ channel blocker (CCB)?
Block voltage gated Ca2+ channel (VGCCs)
- target calcium initiated smooth muscle contraction
What are the three classes of L-type Ca2+ channel blockers?
- dihydropiridines
- benzothiazapines
- phenylalkylamines
What are the advantages of using dihyropyridines?
More selective for peripheral vasculature
- reduced total peripheral resistance