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Cardiology > Lecture 7 - Cardiovascular Pharmacology 1 > Flashcards

Lecture 7 - Cardiovascular Pharmacology 1 Flashcards

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1
Q

Which vessels contain smooth muscle?

A

Arteries, arterooles, veins. Venules have some smooth muscle

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2
Q

What is the role of vascular smooth muscle?

A

Control vascular dilation and constriction of blood vessels

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3
Q

What are vascular smooth muscles innervated by?

A

Sympathetic nerves - control contraction

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4
Q

How does vascular smooth muscle regulated vascular tone?

A

Interaction between vascular smooth muscles and endothelial cells - produce Nitric oxide and endothelin

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5
Q

What does the sympathetic nervous system produce

A

Adrenaline and nor adrenaline

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6
Q

What hormones are circulated?

A

Angiotensin 2 and natriuretic peptides

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7
Q

Describe the mechanism of vascular smooth muscle contraction

A
  1. Angiotensin type 2 type 1 receptors or alpha 1 adrenergic receptors stimulated
  2. This leads to activation of phospholipase C which produces seondary messenger inositol triphosphate.
    This stimulates release of Ca2+ from the sarcoplasmic reticulum and an increase in cytosolic conc of Ca2+.
    Raised Ca2+ binds to and activates calmodulin and that activates myosin light chain kinase . This phosphorylates myosi light chain
  3. Phosphorylated myosin light chain interacts with actin to form actin - myosin cross bridges - intiates vascular smooth cell contraction.
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8
Q

How do vasodilators act?

A

act to decrease vascular tone. reduce contractility of actin - myosin complexes in vascular smooth muscles

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9
Q

What do K+ channel openers do

A

Induce vasodilation by opening ATP sensitive K+ channels: results in hyperpolarization of the cell prevents activation of the voltage gated Ca2+ channels necessary for Ca2+ influx

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10
Q

What do Ca2+ channel blockers do?

A

Cause Vasodilation by reducing the entry o extracellular Ca2+ through L-type Ca2+ channels

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11
Q

What do ACE Inhibitors do?

A

Inhibit vasoconstriction by inhibiting formation of angiotensin 2

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12
Q

Angiotensin 2 type 1 receptor anatogonists?

A

Inihibit vasoconstriction by blocking Angiotensin 2 binding to the receptor

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13
Q

Alpha 1 adrenergic receptor antagonists?

A

Inhibit vasoconstriction by blocking the binding of adrenaline and nor adrenaline to the receptor

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14
Q

What is the major role of Renin - angiotensin aldosterone system

A

Vasoconstriction and sodium retention. Maintains tissue perfusion and increase extracellular fluid volume.

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15
Q

What does overstimulation of RAS do?

A

leads to hypertension and cardiac and vascular remodelling

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16
Q

What produces renin?

A

Juxtaglomerular cells of the kidney

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17
Q

What does renin do?

A

It is a protease that cleaves the prohormone angiotensinogen (produced by the liver) to angiotensin 1

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18
Q

What does ACE do?

A

Converts angiotensin 1 to 2

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19
Q

Where is ACE highly expressed?

A

In the endothelium of the lungs and on other endothelial cells.

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20
Q

ACE has a broad substrate specificity

A

includes bradykinin

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21
Q

Which membrane receptors do angiotensin 2 bind to?

A

AT1 and AT2 receptors

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22
Q

What do juxtglomerular cells express and what happens when they are activated?

A

They express AT1 receptors (vasoconstriction) and when they are activated they inhibit renin secretion. - negative feedback loop

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23
Q

What is angiotensin At1 receptor responsible for?

A
  1. Stimulates aldosterone secretion by the adrenal glands - increases NaCl reabsorption
  2. Vasoconstriction of blood vessels
  3. Sympathtic activation of adrenaline and noradrenaline
  4. Stimulation of thirst - ADH secretion
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24
Q

Angiotensin AT2 receptor

A

Appears to have opposite effects to AT1 including vasodilation (through bradykinin and no release)
expression is mostly foetal but appears again following injury or ischaemia

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25
What effect does ACE i on AT receptors?
They reduce activation of AT1 and AT2 which has a net effect of vasodilation.
26
What does reduced circulating levels of Angiotensin 2 lead to?
Increase circulation of renin and hence more angiotensin 1 formed
27
What effect do ACE i have on bradykinin
They decrease bradykinin degradation in order to help vasodilation and reduce BP through stimulating nitric oxide production in endothelial cells.
28
How do ACE i reduce blood pressure
Decrease levels of Angiotensin 2 and increase levels of bradykinin.
29
ACE i therapeutic uses?
anti-hypertensive, prevent left ventricular hypertrophy, MI, improve haemodynamics of people with congestive heart failure . protection against diabetic and non-diabetic nephropathy , cervical incompetence
30
Adverse effects of ACE i
Cough and angioedema (build up of fluid in the skin )
31
Examples of ACE i
Ramipril, Lisinopril, Enalapril
32
What do angiotensin 2 receptor blockers do?
Inhibit binding of Ang 2 to the AT1 receptor, promote vasodilation. Developed for people with reactions to ACE inhibitors.
33
What effect does ARB have on renin
increases renin levels and ang 1. this in turn leads to increase in Ang 2. Can also increase activation of AT2 receptors.
34
DIfference between ACE i and ARB's
Block Angiotensin binding to receptor and does not affect bradhykinin degradation whereas ace i decrease degradation.
35
ARB's therapeutic uses
Anti-hypertensives - young and diabetics. Less side -effects Still need to monitor renal function/potassium levels
36
Examples of ARB's
Losartan, Valsartan, Candesartan
37
Mechanism of vascular smooth muscle relaxation
Nitric oxde activates guanylyl cyclase by haem-dependent mechanisms. Activation results in elevated levels of cGMP and forms from guanosine triphosphate (GTP). cGMP activates myosin light chain phosphatase via cGMP-dependent protein kinase (PKG). MLCP dephosphorylates myosin light chains and inhibits interaction between phosphorylated myosin LC and actin. reduces formation of actin -myosin cross bridges and hence causes relaxation.
38
What is the role of Nitric oxide?
NO is produced in endothelial cells and plays an important role in vascular tone and platelet aggregation.
39
What factors promote endothelial synthesis of NO?
Shear stress, acetylcholine and bradykinin
40
How is NO useful clinically?
As vasodilatory agents which release NO - used to treat angina GTN spray, or agents whic inhibit cGMP, phosphodiesterase type 5 (Sildenaphil) - erectile dysfunction
41
What is Glyceryl trinitrate used for
is a prodrug - Angina, acute severe hypertension, pulmonary oedema
42
Why is GTN used acutely?
High first pass metabolism - rapid inactivation in the liver by nitrate reductase
43
Side effects of GTN
Mainly effects venous circulation. Side effects are headaches and hypotension
44
What is nitroprusside
powerful vasodilatorm reacts with sulfhydryl groups to give NO. Acts equally on venous and arterial smooth muscle
45
Contra indications of Nitroprusside
Protect from light as it turns to cyanide - hypertensive emergency
46
What should GTN not be used with ?
Not be used together with vasodilators that combat erectile disfunction like Viagra, Cialis or Levitra. - combination can cause hypotension, circulatory collapse and death.
47
Mechanism of vascular smooth muscle relaxation via stimulation of B2 adrenergic receptors
Activates adenylate cyclase which produces cAMP and activates protein kinase which after phosphorylation events 1. Increase in Sarco endoplasmic reticulum Ca activity - stores Ca in SER 2. Increases Plasma membrane Ca activity - Ca transported outside the cell.
48
What is the net result of Mechanism of vascular smooth muscle relaxation via stimulation of B2 adrenergic receptors
Ca 2+ is transported out of the cytosol and so lowers concentration so there is decreased activation of myosin light chain kinase - relaxation reduction in MLCK activity - less myosin light chain kinase phosphorylation - vascular smooth muscle relaxation
49
How do most vasodilators work?
reducing the contractility of actin-myosin complexes through reducing intracellular Ca2+ or dephosphorylation of myosin LC
50
Arterial and venous thrombosis therapies
Percutaneous cornorary intervention ( Angioplasties) Antiplatelet therapies COX 1 inhibition P2Y12 ADP receptor inhibitors alpha 2b Beta 3 integrin inhibitors Antithrombotic therapies - Vitamin K antagonists - Warfarin/Phenindione, Heparin
51
What is a complication of DVT
Pulmonary embolism
52
What is the primary target for arterial thrombosis
Rupture of an atherosclerotic plaque
53
What are the steps of an arterial thrombus formation
adhesion, activation, aggregation of platelets and platelet plug formation
54
What is percutaneous coronary intervention
Non -surgical widening of the coronary artery, using a balloon catheter to dilate the artery and a metal stent is placed. Anti-platelet therapy is important after. involves arterial access via femoral, radial or brachial branches.Guidewire passed into the coronary artery across the stenosis.
55
What are given in high risk procedures
Glycoproein 2b and 2a inhibitors and opiates if angina occurs during angioplasty
56
Types of stents
Bare metal stents | Drug - eluting stents - inhibits smooth muscle cell proliferation
57
After procedure care
Anti- platelets, aspirin indefinitely to reduce CVD risk | usually aspirin and clopidogrel
58
What happens when a plaque ruptures
platelets recruited to site and interact with collagen and von willebrand factor. Primary activation of platelets through thrombin activation. Integrin complex induces binding to fibrinogen - allows cross linking of platelets - further thrombus development. Activation of this receptor complex - final common pathway for platelet aggregation.
59
What are the primary targets of antiplatelet therapy?
Molecules involves in platelet activation and aggregation - inhibit thrombin activation and fibrinogen.
60
What is clopidogrel
an anti-platelet drug
61
What do COX 1 enzymes do?
Involved in protecting GI mucosa and in clotting
62
How does Aspirin work?
Suppresses the production of thromboxanes due to irreversible inactivation of the COX 1 enzyme by platelets.
63
Platelet ADP - receptors
P12Y12 receptors one of the receptors found on the cell surface of platelets involved in irreversible of platelet. Platelet Integrin complex formation for platelet aggregation and is important for cross-linking platelets of fibrin
64
What inhibits P2Y12 ADP receptor inhibition
Phioenopyridines Clopidogrel - most widely used activated by cyt p450 in the liver. irreversibly inhibits P2Y12 ADP receptor. used for patients undergoing PCI
65
What do inhibitors of the glycoprotein 2b/3a receptor complex do?
Designed to reduce platelet aggregation Abciximab - platelet aggregation inhibitor. used during and after procedures like angioplasty so platelets dont stick together eptifibatide - integrilin also antiplatelet drug of glycoprotein 2b/3a inhibitor class
66
What are the triggers of a venous thrombosis
abnormal blood flow altered properties of blood itself alterations in blood vessel wall(endothelium)
67
What are anticoagulants
Treat wide variety of conditions like venous and arterial thrombosis. Main 2 classes - vitamin k antagonists eg. warfarin and heparins - target multiple proteases in cascade
68
What is Vitamin K
Fat soluble vitamin | essential for production of clotting factors - 2,7,9 and 10
69
WARFARIN
Anticoagulant effective and safe for preventing thrombosis and embolism formation. Has to be monitored closely as some medications and food interact with it.
70
difference between anticoagulants and anti-platelets and thrombolytics
Anticoagulants, such as heparin or warfarin (also called Coumadin), work on chemical reactions in your body to lengthen the time it takes to form a blood clot. Antiplatelet drugs, such as aspirin, prevent blood cells called platelets from clumping together to form a clot. Thrombolytics - dissolve clots
71
Mechanism of action of warfarin
Warfarin acts by inhibiting the synthesis of vitamin K-dependent clotting factors, which include Factors II, VII, IX, and X, and the anticoagulant proteins C and S
72
What effects dose of warfarin
Up to 50% of interindividual variability of warfarin dosing due to CYP2C9 and VKORC1 polymorphisms
73
Actions of heparin
Activates antithrombin 3 - serpin Activation leads to a 1000 fold increase in Antithrombin 3 for thrombin and factor 10a intravenous or subcutaneous due to high -ve charge.
74
When is unfractionated heparin used?
Used in combination with anti-platelet agents in acute coronary events
75
Low molecular weight heparins ?
Inactivating factor 10a and are selective. used in prevention and treatment of dvt
76
What are the 2 main types of anti-platelet therapy
Inhibitors of activation (target COX 1 and P2Y12 ADP receptor) Inhibitors of aggregation (target αIIbβ3-integrin complex)
77
What are the anti-thrombotic therapies
Warfarin and heparin
78
How does warfarin act
inhibits vitamin K epoxide reductase | leads to loss of post-translational carboxylation of four coagulation factors (II,VII, IX and X)
79
How does heparin act
``` Heparin (inhibition depends on polymer length) Unfractionated heparins (targets thrombin and Factor Xa) LMW heparins (Factor Xa specific) ```

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