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59 Cards in this Set

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  • Back
Transmembrane receptors with enzymatic cytosolic domains: types
Tyrosine Kinase
Tyrosine Phosphatases
Tyrosine Kinase-associated
Serine/Threnoine Kinases
Guanylyl Cyclases
Transmembrane receptors with enzymatic cytosolic domains: examples
epidermal growth factor
platelet-derived growth factor
atrial natriuretic factor
transforming growth factor-P
enzymatic cytosolic domains
cross-phosphorylation occurs resulting in downstream signaling (kinases)
ligand binding results in endocytosis of receptor; new receptors for via de novo synthesis
almost all second messager systems involve reversible phosphorylation, which performs two principal functions in signaling: amplification and flexible regulation.
median effective dose
median toxic dose
median lethal dose
relates the dose of a drug required to produce a desired effect to that which produces an undesired effect
therapeutic index
the ratio of the TD50 to the ED50 for some therapeutically relevant effect
therapeutic index
dihydrofolate reductase
example of enzyme receptor:
antineoplastic drug methotrexate
transport proteins
Na+/K+ ATPase, the membrane receptor for cardioactive digitalis glycosides
structural proteins
tubulin, the receptor for colchicine, an anti-inflammatory agent
Many of the most useful drugs in clinical medicine act by mimicking or blocking the actions of endogenous ligands that regulate the flow of ions through plasma membrane channels. The natural ligands include acetylcholine, serotonin, γ-aminobutyric acid (GABA), and the excitatory amino acids (eg, glycine, aspartate, and glutamate). All of these agents are synaptic transmitters.
Ligand-Gated Channels
transmembrane receptors: examples
growth hormone
other growth and differentiation regulators
transmembrane ion channels
allow passage of ions and other hydrophilic molecules across plasma membrane
transmembrane ion channels: functions
neurotransmission, cardiac conduction, muscle contraction
transmembrane ion channels: types
1-ligand gated, where binding of ligand to channel causes altered ion conductance
2-voltage-gated, where change in transmembrane voltage gradient causes altered ion conductance
transmembrane ion channels, ligand-gated: examples
synaptic transmitters: acetylcholine, GABA, EAAs (excitatory amino acids: glycine, aspartate, glutamate)
nicotinic acetylcholine receptor can be in closed or open state
in closed state, the channel is occluded by amino acid side chains; in the open state, binding of 2 ACh molecules causes a conformation change that opens the channel
the maximal response that can be produced by a drug
Transmembrane ion channels
allow passage of ions and other hydrophilic molecules across the plasma membrane; can be closed, open, refractory, inactive
Transmembrane ion channels: functions
neruotransmission, cardiac conduction, muscle contraction
ligand-gated transmembrane ion channel domains
extracellular, within the channel or intracellular
voltage-gated transmembrane ion channel states
closed, open or inactivated
ex. block by local anesthetics
Transmembrane G Protein Coupled Receptors
-most abundant class
-receptors transverse the membrane and have intracellular domains that interact with G proteins
Transmembrane G Protein Coupled Receptors: site
extracellular surface of cell membrane
G proteins & second messengers
different ligand are associated with different second messenger system; G protein coupled signaling is involved in many processes
cAMP protein and effector element
G8; adenyl cyclase (converts ATP to cAMP)
G proteins & second messengers: first component
extracellual ligand couples with cell surface receptor
G proteins & second messengers: second component
activation of G protein
G proteins & second messengers: third component
changes the activity of an effector element, usually an enzyme or ion channel
G proteins: function
increase (amplifies signal) cellular second messengers such as cAMP, calcium or phosphoinositides
Intracellular second messengers
cyclic adenosine monophosphate or cAMP; calcuim and phosphoinositides; cyclic guanosine monophosphate (cGMP); kinases
receptor-less drugs
antacids, laxative, chelating agents, osmotic diuretics
types of receptor regulation
receptor desensitization; down regulation; up-regulation
recptor down regulation
produced by agonist-induced decreases in receptor biosynthesis and increases in receptor internalizaion and degradation, usually occurs over hours to days
point where 50% of receptors are bound
maxium effect or efficacy of a drug
EC50 or ED50
concentration or dose required to produce 50% of the maximum effect
concentration of a drug required to produce 50% of that drug's maximal effect (EC50)
potency depends on
the affinity (Kd) of receptors for binding the drug and the efficiency with which drug-receptor interaction is coupled to response
act on receptors to promote the biological response; result is hyperbolic curve on a linear scale
used to get a graded dose-response curve that is a sigmoid curve with a linear midsection that can be more easily analyzed
log concentration of a drug
spare receptors
exist when the maximal response can be elicited when fewer than 100% of the drug's receptors are occupied
spare receptors: how determined
graded dose response curve in which the dose producing the EC50 is less than the dose for Kd50
Kd (point where 50% of receptors are bound)
relationship between bound and free drug concentration; if Kd is low, binding affinity is high; if Kd is high, binding affinity is low
spare receptors: mechanisms
-when the effect of the drug-receptor interaction persists for a much longer time than the interaction itself
-when the actual number of recptors exceed the number of effector molecules available
quantal dose-response curves
percentage or frequency of (all or nothing) patient responses plotted against the log dose of the drug
quantal dose-effect curves
dose of drug rquired to produce a specified magnitude of effect
Efficacy (Emax) is measured how?
With a graded does-response curve, NOT a quantal dose-response curve
Quantal dose-response measures of potency: ED50
median effective dose
Quantal dose-response measures of potency: TD50
toxic dose
Quantal dose-response measures of potency: LD50
lethal dose
Therapeutic Index (TI)
Ratio of TD50 or LD50 to the ED50 determined from quantal-dose response curves
Therapeutic Index (TI)
-an estimate (ppor) of the safety of a drug
-a safe drug is one that has a small effective dose while requiring a very large dose to elicit a toxic response
Therapeutic window
the dosage range between the minimum effective therapeutic concentration (threshold) and the minium toxic concentration (dose)
Therapeutic window
-clinically relevant index of saftey
Certain Safety Factor (CSF)
-the ratio between the dose that is lethal in 1% of the subjects (LD1) and the dose that produces a therapeutic effect in 99% of the subjects (ED99)
Clinical effectiveness of a drug depends on
potency (ED50)
maximal efficacy
ability to reach the relevant receptors (site of action)