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[MT 6314] Pharmacology & Toxicology > Drug Receptors - Pharmacodynamics > Flashcards

Drug Receptors - Pharmacodynamics Flashcards

1
Q

The component of a cell or organism that interacts with a drug and initiates the chain of events leading to the drug’s observed effects.

A

Receptor

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2
Q

T/F: Receptors largely determine the qualitative relations between dose or concentration of drug and pharmacologic effects.

A

F; quantitative

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3
Q

T/F: Receptors are responsible for selectivity of drug action.

A

T

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4
Q

T/F: Receptors mediate the actions of pharmacologic agonists and antagonists.

A

T

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5
Q

Interferes with the ability of an agonist to activate the receptor

A

Antagonist

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6
Q

It used to identify or purify receptor proteins from tissue extracts; consequently, receptors were discovered after the drugs that bind to them.

A

Drug Binding

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7
Q

The best-characterized drug receptors are __________, which mediate the actions of endogenous chemical signals such as neurotransmitters, autacoids, and hormones

A

Regulatory Proteins

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8
Q

The receptor for the antineoplastic drug methotrexate

A

Dihydrofolate reductase

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9
Q

The receptor for statins; and various protein and lipid kinases.

A

3-hydroxy-3-methylglutaryl–coenzyme A (HMG-CoA) reductase

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10
Q

_________ can be useful drug targets.

A

Transport Proteins

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11
Q

The membrane receptor for cardioactive digitalis glycosides

A

Na+/K+- ATPase

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12
Q

The receptor for colchicine, an anti-inflammatory drug

A

Tubulin (Structural Proteins)

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13
Q

Mediates the effects of the most useful therapeutic agents

A

Regulatory Proteins

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14
Q

Best characterized drug receptors

A

Regulatory Proteins

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15
Q

↑ Kd = _ Binding Affinity

A

↓

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16
Q

Smaller EC50 = ____ Potency of the Drug

A

Greater

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17
Q

Molecules that translate the drug-receptor interaction into a change in cellular activity

A

Effectora

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18
Q

T/F: All receptors are effectors.

A

F; Some

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19
Q

A single molecule may incorporate both the drug binding site and the effector mechanism

A

Effectors

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20
Q

The maximal response that can be produced by the drug

A

Emax

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21
Q

The concentration of drug that produces 50% of maximal effect.

A

EC50

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22
Q

Resembles the mass action law that describes the association between two molecules of a given affinity.

A

Hyperbolic Relation

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23
Q

_________________ have been used to confirm this occupancy assumption (Hyperbolic Relation) in many drug-receptor systems

A

Radioactive receptor ligands

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24
Q

The total concentration of receptor sites

A

Bmax

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25
Q

represents the concentration of free drug at which half-maximal binding is observed

A

Kd / Equilibrium Dissociatoon Constant

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26
Q

Response of a particular receptor-effector system is measured against increasing concentration of a drug

A

Graded Dose-Response Curve

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27
Q

↓ EC50 = _____ amount needed to produce 50% = _____ potent drug

A

Smaller; more

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28
Q

Graph of the response versus the drug dose

A

Graded-Dose Response Curve

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29
Q

Maximal response that can be produced by a drug

A

Emax

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30
Q

Emax & Bmax

Are all receptors occupied?

A

Yes

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31
Q

Emax

Is there a response even if the dose is increased?

A

No

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32
Q

Total number of receptor sites

A

Bmax

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33
Q

Measure of the affinity of a drug for its binding site on the receptor

A

Kd

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34
Q

Are often presented as a plot of the drug effect (ordinate) against the logarithm of the dose or concentration (abscissa), transforming the hyperbolic curve into a sigmoid curve with a linear midportion

A

Dose-response data

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35
Q

The overall transduction process that links drug occupancy of receptors and pharmacologic response

A

Coupling

36
Q

The relative efficiency of occupancy-response coupling is determined by

A
  1. Receptor itself
  2. “Downstream” biochemical events
37
Q

Maximal drug response is obtained at less than maximal occupation of the receptors

Not qualitatively different from nonspare receptors, not hidden or unavailable

Temporal in character, when occupied, they can be coupled to respond, there is still effect

A

Spare Receptors

38
Q

Drugs with low binding affinity for receptors will be able to produce full response even at low concentration

A

Spare Receptors

39
Q

Kd (>/<) EC50 with spare receptors

A

>

40
Q

Spare Receptors

T/F: Effect lf the drug-receptor interaction may persist for a longer time than the interaction itself.

A

T

41
Q

Spare receptors may exceed the number of effectors available

A

Yes, as long as they consume the effectors present, kahit dagdagan mo pa, di na tataas yung effect

nakadepend ang effect sa effectors

42
Q

Non-regulatory molecules of the body

A

Inert Binding Sites

43
Q

Binding with these molecules will result to no detectable change in the function of the biologic system

A

Inert Binding Sites

44
Q

Buffers the concentration of the drug

Bound drugs do not contribute directly to the concentration gradient that drives diffusion

A

Inert Binding Sites

45
Q

Binds to the receptor and directly or indirectly bring about an effect

Full activation of the effector system

A

Agonist

46
Q

Produces less than the full effect, even when it has saturated the receptors

Acts as an inhibitor in the presence of a full agonist

A

Partial Agonist

47
Q

Binds but do not activate the receptors

Blocks / competes with agonist

A

Antagonist

48
Q

Classification of Antagonist

A
  1. Competitive Antagonist
  2. Irreversible Antagonist
  3. Chemical Antagonist
  4. Physiologic Antanogist
49
Q

Competes with agonist receptor

Binds to the receptor reversibly without activating the effector system

A

Competitive Antagonist

50
Q

T/F: Spare receptors may be demonstrated by using irreversible antagonists to prevent binding of agonist to a proportion of available receptors and showing that high concentrations of agonist can still produce an undiminished maximal response

A

T

51
Q

Antagonist (increases/decreases) the agonist concentration needed for a given degree of response

A

increases

52
Q

2 Therapeutic Implications of Competitive Antagonist

A

(1) Degree of inhibition produced by the competitive antagonist depends on the concentration of
antagonist (eg, propranolol)
(2) Clinical response to a competitive antagonist
depends on the concentration of agonist that is competing for binding to the receptor

53
Q

Antagonist that will not achieve maximal effect

A

Irreversible Antagonist

54
Q

Binds with the receptor via covalent bonds

Receptor is mot available to bind the agonist

A

Irreversible Antagonist

55
Q

More dependent on the rate of turnover of receptors

A

Irreversible Antagonists

56
Q

Concentration-effect curve moves downward

No shift of the curve in the dose axis

Emax is not reached

No increase in median effective dose (ED50) unless there are spare receptors

A

Irreversible Antagonist

57
Q

Does not depend on interaction with the agonist’s receptor

Drug that interacts directly with the drug being antagonized to remove it or to prevent it from reaching its target

A

Chemical Antagonism

58
Q

Makes use of the regulatory pathway

Effects that are less specific & less easy to control

A

Physiologic Antagonism

59
Q

Binds to a different receptor producing an effect opposite to that produced by the drug it is antagonizing

A

Physiologic Antagonism

60
Q

The total number of receptors present compared with the number actually needed to elicit a maximal biologic response.

A

Degree of Spareness

61
Q

The concentration (C′) of an agonist required to produce a given effect in the presence of a fixed concentration ([I]) of competitive antagonist is greater than the agonist concentration (C) required to produce the same effect in the absence of the antagonist. The ratio of these two agonist concentrations (called the dose ratio) is related to the dissociation constant (Ki ) of the antagonist

A

Schild Equation

62
Q

Occurs when a drug reduces the concentration of an agonist by forming a chemical complex

A

Chemical Antagonism

63
Q

T/F: some types of antagonism do not involve a receptor at all

A

T

64
Q

Binding to a different site “allosterically” on the receptor relative to the classical “orthosteric” site bound by the agonist.

A

Allosteric Modulators

65
Q

Can also bind at targets lacking a known orthosteric
binding site

A

Allosteric Modulators

66
Q

potentiate the receptor activity

A

Positive Allosteric Modulators

67
Q

reduce the receptor activity

A

Megative Allosteric Modulators

68
Q

Produce concentration-effect curves that resemble those observed with full agonists in the presence of an antagonist that irreversibly blocks some of the receptor sites.

A

Partial Agonists

69
Q

T/F: Failure of partial agonists to produce a maximal response is not due to decreased affinity for binding to receptors.

A

T

70
Q

competitively inhibit the responses produced by full agonists

A

Partial Agonists

71
Q

Intracellular molecules that translate the drug-receptor interaction into a change in cellular activity (e.g. adenylyl cyclase)

A

Effectors

72
Q

Bind to receptors but do not activate them

A

Receptor Antagonists

73
Q

T/F: Most effectors are found inside the cell

A

F; surface of the cell

74
Q

T/F: A single molecule may incorporate both the drug binding site and the effector mechanism

A

T

75
Q

↑ PA Occupancy = _ FA Binding

A

↓

76
Q

PA = _ Maximal Response

A

↓

77
Q

Transmembrane Signaling Mechanisms

A

1: A lipid-soluble chemical signal crosses the plasma membrane and acts on an intracellular receptor (which may be an enzyme or a regulator of gene transcription);

2: the signal binds to the extracellular domain of a transmembrane protein, thereby activating an enzymatic activity of its cytoplasmic domain;

3: the signal binds to the extracellular domain of a transmembrane receptor bound to a separate protein tyrosine kinase, which it activates;

4: the signal binds to and directly regulates the opening of an ion channel;

5: the signal binds to a cell-surface receptor linked to an effector enzyme by a G protein.

78
Q

______ hormone, whose receptors stimulate the transcription of genes by binding to specific DNA sequences (often called ________) near the gene whose expression is to be regulated.

A

Thyroid; Response Elements

79
Q

allows the DNA-binding and transcription-activating domains of the receptor to fold into their functionally active conformations, so that the activated receptor can initiate transcription of target genes.

A

hsp90

80
Q

The mechanism used by hormones that act by regulating gene expression has two therapeutically important consequences:

A
  1. All of these hormones produce their effects after a characteristic lag period of 30 minutes to several hours.
  2. The effects lf these agents can persist for hours / days after the agonist concentration has been reduced to zero.
81
Q

Mediates hormonal responses

A

cAMP (Cyclic adenosine monophosphate)

82
Q

These receptors are polypeptides consisting of an extracellular hormone-binding domain and a cytoplasmic enzyme domain, which may be a protein tyrosine kinase, a serine kinase, or a guanylyl cyclase

A

Ligand-Regulated Transmembrane Enzymes

83
Q

The intensity and duration of action of EGF, PDGF, and other agents that act via receptor tyrosine kinases are often limited by a process called ___________.

A

Receptor down-regulation

84
Q

respond to a heterogeneous group of peptide ligands, which include growth hormone, erythropoietin, several kinds of interferon, and other regulators of growth and differentiation.

A

Cytokine Receptors

85
Q

A separate protein tyrosine kinase, from the _______ family, binds noncovalently to the cytokine receptor.

A

Janus-kinase (JAK)

86
Q

Tyrosine kinase signaling function sequence

A
  1. Binding of Ligand
  2. Dimerization
  3. Activates the tyrosine kinase enzyme activity (phosphorylation)
  4. Phosphorykation of tyrosine residues
  5. Binding of EGF
  6. The receptor converts from its inactive monomeric state to an active dimeric state
    7, The cytoplasmic domains become phosphorylated (P) on specific tyrosine residues (Y), then enzymatic activities are activated
  7. Phosphorylation of substrate proteins (S).
87
Q

bind to the extracellular domain of a particular receptor and interfere with binding of growth factor.

membrane permeant small molecule chemicals (eg,
gefitinib, erlotinib)

inhibit the receptor’s kinase activity in the cytoplasm

A

Inhinitors of tyrosine kinases / Monoclonal antibodies

[MT 6314] Pharmacology & Toxicology (20 decks)

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