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IC > Vasoactive Peptides > Flashcards

Vasoactive Peptides Flashcards

1
Q

Vasoactive peptides

A

polypeptide hormones, transmitters that have roles in ANS and CNS
-important effects on vascular and other smooth muscles, mediators of inflammation

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2
Q

Vasoconstrictors

A

angiotensin II, vasopressin, endothelins, neuropeptide Y

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3
Q

Vasodilators

A

bradykinin and other kinins, natriuretic peptides, vasoactive intestinal peptide, substance P, neurotensin, calcitonin gene-related peptide

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4
Q

Biosynthesis of angiotensin

A
  • Angiotensinogen synthesized in liver as initial substrate and ciruclates in blood stream
  • Renin secreted from kidneys, and cleaves angiotensinogen–> angiotensin I (removal of last 4 AA)
  • Angiotensin I has little or no bio activity but circulates in blood stream
  • Angiotensin I converted to Ang II by ACE (Angiogensin converting enzyme)
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5
Q

Renin-angiotensin system

A
  • driven by SNS
  • long term regulation of CV fxn complementing short term NE release on peripheral vasculature
  • primary mediator is ang II
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6
Q

Renin secretion

A
  • Renin synthesized and stored in juxtaglomerular apparatus of nephron in kidney
  • Granular cells are site of synthesis, storage, and release of renin
  • Location of macula densa beside renin secreting JG cells in afferent arteriole and regulates renin secretion
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7
Q

Renin secretion inhibited by

A

1) inc NaCl flux thru chemoreceptors in macula densa
2) elevated BP thru baroreceptors in afferent arteriole wall
3) b-adrenergic blockade by inhibiting sympathetic stimulation via b1 adrenergic receptors
4) negative feedback by angiotensin II

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8
Q

Actions of Ang II

A
  • Inc peripheral resistance to inc afterload
  • Stimulate aldosterone secretion to inc fluid volume and plasma volume and inc preload
  • direct vasoconstrictor
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9
Q

ACE inhibitors will act

A

oppositely to decrease both preload and afterload

-also protect against subsequent failure by slowing remodeling after MI

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10
Q

ACE inhibitors

A
  • pril
  • all are prodrugs except for captopril
  • all ACE inh are equally effective in blocking conv of Ang I to Ang II
  • same clinical uses and same AE
  • Inhibit converting enzyme that is happening mainly in lung
  • Lower BP via reduced angiotensin vasoconstriction, dec aldosterone release which will dec blood volume and CO, red destruction of bradykinin (potent vasodilator, enhance BP lowering)

AE: cough and edema because inc bradykinin located in lungs and activation of sensory nerves in lung
-Also may increase renin release because diminishing neg feedback by ang II

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11
Q

Toxicity of ACE inhibitors

A

-cough, angioedema, hyperkalemia due to inhibited aldosterone secretion esp in pts with renal insufficiency, teratogen

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12
Q

Angiotensin Receptor Antagonist

A

Mainly selective for AT1

  • may cause hyperkalemia esp in pts with renal insuf
  • more specific in blocking ang effects because they do not affect bradykinin metabolism (no coughing or angioneurotic edema), but lose potential added benefit of circulating bradykinin levels
  • losartan
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13
Q

AT1r

A

Predominate in vascular smooth muscle in adults

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14
Q

AT2r

A

occur mainly in fetal tissues

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15
Q

Renin inhibitors

A

Aliskerin

  • reduction in plasma renin activity and ang I and II and aldosterone concentrations
  • red bp similar to those produced by ang II receptor antagonist
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16
Q

Sympatholytic drugs will also inhibit

A

secretion of renin
-beta blocker will act to lower renin and ang levels as well- indirect modifier because there are beta receptors that lead to renin release when acted on by catecholamines

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17
Q

Bradykinins and kalladin

A
  • arteriodilators formed by enzymes called kallikreins and act on protein substrates called kininogens
  • kinins released from pancreas, kidney, salivary glands, sweat
  • inflammation effects promote redness, pain, swelling (leaky endothelium), heat
  • produce pain
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18
Q

kallikreins

A

present in plasma and many tissues

form kinins

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19
Q

kininogens

A

present in plasma, lymph, interstitual fluid

acted on by kallikreins

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20
Q

B1 kinin receptor

A

limited tissue distribution and fxn

21
Q

B2 kinin receptor

A

widely distributed and cause most biological effects

22
Q

b2 receptor antagonist

A
  • icatibant

- used experimentally to evaluate kinin involvement in pain, hyperalgesia, inflammation; not available for clinical use

23
Q

b2 receptor agonist

A

may be useful for htn and CHF

24
Q

what contributes to antihtn effects of ACE inhibitors

A

bradykinin induced vasodilation- because ACE inh reduce bradykinin destruction and elevate plasma bradykinin levels

25
Q

Vasopressin

A
  • Antidiuretic hormone (ADH)
  • Synthesized in hypothalamus w/ oxytocin and secreted or released from post pit
  • produces antiduiretic and vasopressor effects by acting on 3 receptors V1a, V1b, V2
  • may constrict coronary blood vessels in pts with CAD
26
Q

V1a receptors

A

in VSM cause vasoconstriction and inc bp

-receptor antagonists

27
Q

V1b receptors

A

potentiate release of ACTH in pituitary

28
Q

V2 receptors

A

in renal cells produce antidiuresis by inc water permeability and reabsorption in collecting tubules

29
Q

desmopressin

A
  • synthetic variant
  • mostly V2 receptor action
  • antidiuretic effect is more potent than vasoconstriction effect- more selective towards fluid retention side
  • used to tx diabetes insipidus
30
Q

Diabetes insipidus can be treated with

A

vasopressin and desmopressin

31
Q

conivaptan

A

v1a and v2 (vasopressin receptor) antagonist - used to treat hyponatremia
-will lead to sodium retention

32
Q

endothelins

A

potent vasoconstrictor substances
-locally acting
-et1, et2, et3
direct positive inotropy and chronotropy
-rapid and transient BP decrease but prolonged inc in BP
-Contract bronchial smooth muscle
-Dec glomerular filtration and sodium, water excretion
-inc secretion of renin, aldosterone, vasopressin, anp

33
Q

ETA receptor

A

endothelin a receptor

-on smooth muscles, promotes vasoconstriction

34
Q

ETB receptor

A

endothelial release of EDRF (endothelium derived relaxation factor- NO) and prostanoids (similar to muscarinic effect or histamine)

35
Q

Bosentan

A
  • nonselective ETA/ETB receptor antagonist
  • approved for pulmonary htn
  • AE: systemic hypotension, hepatotoxicity
36
Q

Phosphoramidon

A

endothelin converting enzyme inhibitor

-non specific for endothelin converting enzyme

37
Q

Substance P

A
  • 11 amino acid tachykinin peptide
  • Rapidly acting vasodilator
  • contracts intestinal, bronchiolar smooth muscle
  • Stimulates glandular secretion
  • NT in CNS and enteric NS
  • inflammatory mediator in periphery
  • Makes endothelium leaky
38
Q

Other tachykinins

A

Neurokinin A, neurokinin B

39
Q

three G protein coupled neurokinin receptors are

A

NK1, NK2, NK3

40
Q

Nonpeptide NK1 receptor antagonists

A
  • developed as potential analgesics, under trial as antidepressants
  • prevents chemotherapy induced emesis
41
Q

CGRP

A

Calcitonin gene related peptide

  • distributed widely in CNS and PNS
  • most potent vasodilator yet discovered
  • release of CGRP from trigeminal nerves may produce migraine
  • 2 receptors: CGRP1 and CGRP2
42
Q

Neuropeptide Y

A
  • one of the most abundant neuropeptides in CNS and PNS

- frequently colocalized in noradrenergic neurons in NE

43
Q

Effects of neuropeptide Y in CNS

A

increased feeding, hypotension, hypothermia, and resp depression

44
Q

Effects of neuropeptide Y in PeripheralNS

A

Vasoconstriction of cerebral blood vessel, positive inotropic and chronotropic actions, hypertension
-When released NE will provide slow, long lasting vasoconstriction

45
Q

Neuropeptide Y receptors

A

Y1- cardiovascular and peripheral effects

Y5- CNS control of food intake

46
Q

Vasopeptidase inhibitors

A

Many vasoactive peptides are inactivated by endopeptidases

  • vasopeptidase inhibitors inhibit both ACE and neutral endopeptidase- increase levels of natriuretic peptides and decrease formation of angiotensin II
  • enhance vasodilation, reduce vasoconstriction, increase sodium excretion
  • decrease peripheral vascular resistance and blood pressure
  • produce angioedema and cough (because they inhibit ACE)
47
Q

ACE inhibitor list

A

-prils

benazepril, captopril, enalapril, fosinopril, lisinopril, moexipril, perindopril, quinapril, ramipril, trandolapril

48
Q

Ang receptor antagonist

A

-sartans

candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan

49
Q

Neurokinin-1 receptor antagonist

A

Aprepitant

IC (31 decks)

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