[SIM] Mechanism of Drug Action Flashcards
What is the receptor for Norepinephrine?
Beta-2
What is responsible for phosphorylation of Myosin?
Myosin Light Chain Kinase
What state does Myosin have to be to have a greater affinity for Actin in muscle contraction?
Phosphorylated
Function: Salbutamol
Binds to B2 Adrenergic Receptors, mimicking Norepinephrine causing relaxation of airways
Differentiate Salbutamol at Low Doses and High Doses
Low Dose: Specific to B2 Adrenergic Receptors
High Dose: Decreased specificity to B2 Adrenergic Receptors; may cause tremors and tachycardia
What are the receptors of Acetylcholine?
Nicotinic
Muscarinic
[Type of Receptor]
Nicotinic
Ionotropic
[Type of Receptor]
Muscarinic
G Protein Coupled Receptor
Phospholipase C/IP3 Pathway
Function: M2 Receptors
Bringing the heart back to normal after actions of the sympathetic nervous system
Components: Atropine
What is the component responsible for most of its physiologic effects?
D-Hyoscyamine
L-Hyoscyamine
L-Hyoscyamine
This is a competitive inhibitor of Acetylcholine
Atropine
[Type of Receptor]
Insulin
Ligand-gated Tyrosine Protein Kinase
Components of Insulin Receptors
2 Alpha Subunits
2 Beta Subunits
Linked by disulfide bonds
Where is the insulin-binding domain located?
Extracellular Alpha Sub-units
Which component of the insulin receptor has the cytoplasmic kinase activity?
Beta Sub-unit
Effect of Tyrosine Kinase Receptor Activation (Insulin Receptors)
Releases Phosphatidyl Inositol-3-Phosphate (PI3P) and increases the number of GLUT4 on the outer membrane, allowing entry of Glucose into the cell
What causes Type II Diabetes?
Insulin insensitivity or decrease in Insulin Receptor Signaling
Differentiate Tyrosine Kinase receptors from GPCRs in terms of Gene Expression
Tyrosine Kinases affect downstream events in gene expression
What is the most prevalent form of Estradiol and Estrone?
Estrogen
Where is Estrogen produced?
Ovaries
2 Main Targets of Estrogen
Breast
Uterus
Estrogen receptors are stabilized by?
Heat Shock Proteins
HSP90
Differentiate the 2 Kinds of Estrogen Receptors
- ER-Alpha
- Made up of 500 AAs
- Mostly in Endometrium and Breast Cancer - ER-Beta
- Made up of 600 AAs
- Present in Granulose Cells and Osteoblasts
What activates transcription in the ER-Alpha Receptor?
ER-Alpha:Estradiol Complex
What do Breast Tumor Cells need for growth and proliferation?
Estrogen
Drug for Breast Cancer Patients
How does it work?
Tamoxifen
Competitive, partial agonist inhibitor of Estrogen
Tamoxifen requires processing in the liver to become this activate metabolite that has a higher affinity to Estrogen Receptors
4-Hydroxytamoxifen (Endoxifen)
Limitations of Tamoxifen Therapy
- Only efffective in women who have ER+ BRCA
2. More than 1/3rd of these do not respond to Tamoxifen though
Lack of this liver enzyme may interfere with Tamoxifen metabolite production
Cytochrome P450 2D6
CYP2D6 and CYA3P4
2 Mechanisms of Sensitization
Homologous
Heterologous
Differentiate Homologous and Heterologous Sensitization
Homo: Loss of responsiveness of the specific receptor that has been exposed repeatedly
Hetero: Desensitization of one receptor also results in desensitization of another receptor not directly activated by agonist in question
Function: Chelating Agent
Prevent/Reverse heavy metal toxicity on enzymes or cellular targets by binding to them
Used for serious lead poisoning and lead encephalopathy
Ethylene Diamine Tetraacetate
CaNaEDTA
[Treatment]
Dimercaprol
Arsenic, Mercury, Gold, Lead, Antimony, and other Toxic Metal Poisoning
[Treatment]
Succimer
Lead Poisoning
[Treatment]
Penicillamine
Copper Poisoning
[Treatment]
Antacids
Patients with dyspepsia and acid-peptic diseases
[Treatment]
Mannitol
Use to treat oliguric phase of ARF
Promotes the excretion of toxic substances
Use to reduce intracranial pressure
Used in the treatment of cerebral edema
[Treatment]
Ammonium Chloride
Lowers blood pH after being metabolized to Urea and Hydrochloric Acid
[Treatment]
Ascorbic Acid
Acidifies urine, providing hydrogen ions and lowering urine pH
[Treatment]
Acetazolamide
Increases excretion of Bicarbonate Ions, lowering blood pH
Who experimented on chicks (the animal) with Curare and Nicotine?
Langley (1905)
Any cellular macromolecule that a drug binds to initiate its effects; a component of the organism with which a drug acts in some specific manner to cause an action which results to observable effects
Receptor
Agents that bind to receptors (include drugs, hormones, autacoids, growth factors, neurotransmitters, etc.)
Ligands
An agent that elicits a biological effect by binding to a receptor.
Agonist
Drugs binding to receptors but do not initiate change in cellular function. Blocks the binding of agonists.
An agent that by itself is devoid of biological activity but binds to the receptor and prevents the biological effect of an endogenous agonist.
Antagonist
Endogenous substances (generated by the agent-receptor complex which) which serve as signaling mechanisms that enable drugs/endogenous substance to exert their biologic effects.
Second Messengers
The measure of tightness with which a drug binds to a receptor.
Affinity
Measure of the ability of a drug, once bound to the receptor, to produce measurable physiologic effects
Intrinsic Activity
Receptors are present in finite numbers.
Saturability
Binding is a noncovalent interaction due to weak intermolecular forces.
Reversibility
Many natural occurring agonists exist as optical isomers (+ or -, l or d, S or R); preference for naturally- occurring stereoisomers (e.g. 1- vs d-norepinephrine)
Stereoselectivity
Preference for specific or closely related, agonist and should not recognize chemically dissimilar endogenous agents
Agonist Specificity
Binding should be present in tissues known to be biologically sensitive to the hormone/drug and should take place at concentrations consistent with the physiological concentrations of the endogenous agents
Tissue Specificity
Neurotransmitter used by all motor neurons
Acetylcholine
Components of Acetylcholine Receptors
5 Subunits:
2 Alpha Sub-units
1 Beta Sub-unit
1 Gamma Sub-unit
1 Delta Sub-unit
How many units of Acetylcholine is needed to activate the Nicotinic Acetylcholine Receptor?
2
[Treatment]
Turbocurarine
Neuromuscular blocking drug
Skeletal muscle relaxant
[Mechanism of Action]
Turbocurarine
Competitive antagonist of ACH that acts predominantly on Nicotinic Receptor Sites
Where are the Nicotinic Receptor Sites found on the ACH Receptors?
Alpha Sub-units
Differentiate Tachyphylaxis and Tolerance
Tachyphylaxis: Rapid desensitization as a result of acute effects
Tolerance: Long term effect